| VIVINT APX |
| VIVINT APX The vivint company sign me up for another 36 month with out nitifiying me they say it was on the contract for an outomatic renew Irving , |
| 4th of Jul, 2011 by User964276 |
Vivint alarm company has sign me up for another 36 month contract because they stated that is in the contract and I sign it I told them that I sign the contract because they installed the system the first 36 month but not the second time.They did not get my approval and I did not authorize it in any shape or form, my contract ended in June and I gave them a call in July 5th,2011 because I did remember when my contract was over and it turn out to be in June 2011 and I was practically 1 day late cause of the holidays to late to cancel the contract and they automatically reinstated my contract.
They said they cannot cancel because I owe them around 500 dollars for the upcoming 36 month that I did not sign for.
Why can I not cancel after fulfilling my 36 month term?why do they need another contract? |
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A primate ( /?pra?me?t/ US dict: pr??·m?t) is a mammal of the order Primates ( /pra??me?ti?z/ US dict: pr?·m??·t?z; Latin: "prime, first rank"), [2] which contains prosimians (including lemurs, lorises, galagos and tarsiers) and simians (monkeys and apes – including humans).[3] Primates arose from ancestors that lived in the trees of tropical forests; many primate characteristics represent adaptations to life in this challenging three-dimensional environment. All but a few primate species remain at least partly arboreal.
With the exception of humans, who inhabit every continent, [a] most primates live in tropical or subtropical regions of the Americas, Africa and Asia.[4] Primates range in size from Madame Berthe's mouse lemur, which weighs only 30 grams (1 oz), to the mountain gorilla, weighing 200 kilograms (440 lb). According to fossil evidence, the primitive ancestors of primates may have existed in the late Cretaceous period around 65 million years ago; the oldest known primate is the Late Paleocene Plesiadapis, c. 55–58 million years ago.[5] Molecular clock studies suggest that the primate branch may be even older, originating in the mid-Cretaceous period around 85 mya.[5]
Order Primates has traditionally been divided into two main groupings: prosimians and anthropoids (simians). Prosimians have characteristics more like those of the earliest primates, and include the lemurs of Madagascar, lorisiforms and tarsiers. Simians include the monkeys and apes. More recently, taxonomists have preferred to split primates into the suborder Strepsirrhini, or curly-nosed primates, consisting of non-tarsier prosimians, and the suborder Haplorhini, or dry-nosed primates, consisting of tarsiers and the simians. Simians are divided into two groups: platyrrhine ("flat nosed") or New World monkeys of South and Central America and catarrhine (narrow nosed) monkeys and apes of Africa and southeastern Asia. New World monkeys include the capuchin, howler and squirrel monkeys; catarrhines consist of Old World monkeys (such as baboons and macaques), gibbons and great apes. Humans are the only extant catarrhines that have spread successfully outside of Africa, South Asia, and East Asia, although fossil evidence shows many other species were formerly present in Europe.
Considered generalist mammals, primates exhibit a wide range of characteristics. Some primates (including some great apes and baboons) are primarily terrestrial rather than arboreal, but all species possess adaptations for climbing trees. Locomotion techniques used include leaping from tree to tree, walking on two or four limbs, knuckle-walking, and swinging between branches of trees (known as brachiation). Primates are characterized by large brains relative to other mammals, as well as an increased reliance on stereoscopic vision at the expense of smell, the dominant sensory system in most mammals. These features are more developed in monkeys and apes and noticeably less so in lorises and lemurs. Three-color vision has developed in some primates. Most also have opposable thumbs and some have prehensile tails. Many species are sexually dimorphic, which means males and females have different physical traits, including body mass, canine tooth size, and coloration. Primates have slower rates of development than other similarly sized mammals and reach maturity later but have longer lifespans. Depending on the species, adults may live in solitude, in male–female pairs, or in groups of up to hundreds of members.
Contents [hide]
1 Evolutionary history
1.1 Evolution
1.2 Classification of living primates
1.3 Hybrids
2 Distinguishing features
3 Anatomy, physiology, and morphology
3.1 Sexual dimorphism
3.2 Locomotion
4 Behavior
4.1 Social systems
4.2 Interspecific associations
4.3 Cognition and communication
4.4 Life history
4.5 Diet and feeding
5 Habitat and distribution
6 Interactions between humans and other primates
6.1 Legal and social status
6.2 Role in scientific research
6.3 Conservation
7 See also
8 Footnotes
9 References
10 Further reading
11 External links
[edit]Evolutionary history
Euarchontoglires
Glires
Rodentia (rodents)
Lagomorpha (rabbits, hares, pikas)
Euarchonta
Scandentia (treeshrews)
Primatomorpha
Dermoptera (colugos)
†Plesiadapiformes
Primates
Order Primates is part of the clade Euarchontoglires, which is nested within the clade Eutheria of Class Mammalia. Recent molecular genetic research on primates, colugos, and treeshrews has shown that the two species of colugos are more closely related to primates than treeshrews, [6] even though treeshrews were at one time considered primates.[7] These three orders make up the clade Euarchonta. The combination of this clade with the clade Glires (composed of Rodentia and Lagomorpha) forms the clade Euarchontoglires. Variously, both Euarchonta and Euarchontoglires are ranked as superorders. Some scientists consider Dermoptera a suborder of Primates and call the "true" primates the suborder Euprimates.[8]
[edit]Evolution
Further information: List of fossil primates and Lemur evolutionary history
The primate lineage is thought to go back at least 65 mya (million years ago), [9] even though the oldest known primate from the fossil record is Plesiadapis (c. 55–58 mya) from the Late Paleocene.[10][11] Other studies, including molecular clock studies, have estimated the origin of the primate branch to have been in the mid-Cretaceous period, around 85 mya.[12][13][14]
By modern cladistic reckoning, Order Primates is monophyletic. Suborder Strepsirrhini, the curly-nosed or "wet-nosed" primates, is generally thought to have split off from the primitive primate line about 63 mya, [15] although earlier dates are also supported.[16] The seven strepsirhine families are the five related lemur families and the two remaining families that include the lorisids and the galagos.[1][17] Older classification schemes wrap Lepilemuridae into Lemuridae and Galagidae into Lorisidae, yielding a four-one family distribution instead of five-two as presented here.[1] During the Eocene, most of the northern continents were dominated by two groups, the adapiforms and the omomyids.[18][19] The former are considered members of Strepsirrhini, but did not have a toothcomb like modern lemurs; recent analysis has suggested Darwinius masillae fits into this grouping.[20] The latter was related closely to tarsiers, monkeys, and apes. It is unclear exactly how these two groups relate to extant primates. Omomyids perished about 30 mya, [19] while adapids survived until about 10 mya.[21]
Ring-tailed lemur, a strepsirrhine primate
According to genetic studies, the lemurs of Madagascar diverged from the lorisiforms approximately 75 mya.[16] These studies, as well as chromosomal and molecular evidence, also show that lemurs are more closely related to each other than to other strepsirrhine primates.[16][22] However, Madagascar split from Africa 160 mya and from India 90 mya.[23] To account for these facts, it is thought that a founding lemur population of a few individuals reached Madagascar from Africa via a single rafting event between 50 and 80 million years ago.[16][22][23] Other colonization options have been examined, such as multiple colonizations from Africa and India, but none are supported by the genetic and molecular evidence.[18]
Until recently the aye-aye has been difficult to place within Strepsirrhini.[1] Theories had been proposed that its family, Daubentoniidae, was either a lemuriform primate (meaning its ancestors split from the lemur line more recently than lemurs and lorises split) or a sister group to all the other strepsirrhines. In 2008, the aye-aye family was confirmed to be most closely related to the other Malagasy lemurs, likely having descended from the same ancestral population that colonized the island.[16]
Suborder Haplorhini, the simple-nosed or "dry-nosed" primates, is composed of two sister clades.[1] Prosimian tarsiers in the family Tarsiidae (monotypic in its own infraorder Tarsiiformes), represent the most basal division, originating about 58 mya.[24][25] The infraorder Simiiformes emerged about 40 mya, [19] and contains two clades, both parvorders: Platyrrhini, which developed in South America, consisting of New World monkeys, and Catarrhini, which developed in Africa, consisting of Old World monkeys, humans and the other apes.[1] A third clade, which included the eosimiids, developed in Asia but went extinct millions of years ago.[26]
As in the case of lemurs, the origin of New World monkeys is unclear. Molecular studies of concatenated nuclear sequences have yielded a widely varying estimated date of divergence between platyrrhines and catarrhines, ranging from 33 to 70 mya, while studies based on mitochondrial sequences produce a narrower range of 35 to 43 mya.[5][27] It is possible that anthropoid primates traversed the Atlantic ocean from Africa to South America during the Eocene by island hopping, facilitated by Atlantic Ocean ridges and a lowered sea level.[18] Alternatively, a single rafting event may explain this transoceanic colonization. Due to continental drift, the Atlantic Ocean was not nearly as wide at the time as it is today.[18] Research suggests that a small 1 kg (2.2 lb) primate could have survived 13 days on a raft of vegetation.[28] Given estimated current and wind speeds, this would have provided enough time to make the voyage between the continents.
Emperor tamarin, a New World monkey
Apes and monkeys spread from Africa into Europe and Asia starting in the Miocene.[29] Soon after, the lorises and tarsiers made the same journey. The first hominid fossils were discovered in Northern Africa and date back 5–8 mya.[19] Old World monkeys disappeared from Europe about 1.8 mya.[30] Molecular and fossil studies generally show that modern humans originated in Africa 100, 000–200, 000 years ago.[31]
Although primates are well studied in comparison to other animal groups, several new species have been recently discovered, and genetic tests have revealed previously unrecognised species in known populations. Primate Taxonomy listed about 350 species of primates in 2001;[32] the author, Colin Groves, increased that number to 376 for his contribution to the third edition of Mammal Species of the World (MSW3).[1] However, publications since the taxonomy in MSW3 was compiled in 2003 have pushed the number to 424 species, or 658 including subspecies.[33]
[edit]Classification of living primates
A 1927 drawing of chimpanzees, a gibbon (top right) and two orangutans (center and bottom center). The chimp in the upper left is brachiating; the orangutan at the bottom center is knuckle-walking.
Homo sapiens, a member of the order Primates
The following is the listing of the various families of primates:[1][17][33]
Order Primates
Suborder Strepsirrhini: non-tarsier prosimians
Infraorder Lemuriformes
Family Cheirogaleidae: dwarf lemurs and mouse-lemurs (32 species)
Family Daubentoniidae: aye-aye (1 species)
Family Lemuridae: lemurs (22 species)
Family Lepilemuridae: sportive lemurs (26 species)
Family Indriidae: woolly lemurs and allies (19 species)
Infraorder Lorisiformes
Family Lorisidae: lorises, pottos and allies (9 species)
Family Galagidae: galagos (19 species)
Suborder Haplorhini: tarsiers, monkeys and apes
Infraorder Tarsiiformes
Family Tarsiidae: tarsiers (9 species)
Infraorder Anthropoidea
Parvorder Platyrrhini: New World monkeys
Family Callitrichidae: marmosets and tamarins (42 species)
Family Cebidae: capuchins and squirrel monkeys (17 species)
Family Aotidae: night or owl monkeys (douroucoulis) (10 species)
Family Pitheciidae: titis, sakis and uakaris (42 species)
Family Atelidae: howler, spider, woolly spider and woolly monkeys (28 species)
Parvorder Catarrhini
Superfamily Cercopithecoidea
Family Cercopithecidae: Old World monkeys (135 species)
Superfamily Hominoidea
Family Hylobatidae: gibbons or "lesser apes" (13 species)
Family Hominidae: great apes, including humans (7 species)
Philippine tarsier, once considered a prosimian, now predominantly considered a haplorrhine
Order Primates was established by Carl Linnaeus in 1758, in the tenth edition of his book Systema Naturae, [34] for the genera Homo (humans), Simia (other apes and monkeys), Lemur (prosimians) and Vespertilio (bats). In the first edition of the same book (1735), he had used the name Anthropomorpha for Homo, Simia and Bradypus (sloths).[35] In 1839, Henri Marie Ducrotay de Blainville, following Linnaeus and imitating his nomenclature, established the orders Secundates (including the suborders Chiroptera, Insectivora and Carnivora), Tertiates (or Glires) and Quaternates (including Gravigrada, Pachydermata and Ruminantia), [36] but these new taxa were not accepted.
Before Anderson and Jones introduced the classification of Strepsirhini and Haplorhini in 1984, [37] (followed by McKenna and Bell's 1997 work Classification of Mammals: Above the species level), [38] the Primates were divided into two superfamilies: Prosimii and Anthropoidea.[39] Prosimii included all of the prosimians: Strepsirrhini plus the tarsiers. Anthropoidea contained all of the simians.
[edit]Hybrids
Primate hybrids usually arise in captivity, [40] but there have also been examples in the wild.[41][42] Hybridization occurs where two species' range overlap to form hybrid zones; hybrids may be created by humans when animals are placed in zoos or due to environmental pressures such as predation.[41] Intergeneric hybridizations, hybrids of different genera, have also been found in the wild. Although they belong to genera that have been distinct for several million years, interbreeding still occurs between the gelada and the Hamadryas baboon.[43]
[edit]Distinguishing features
Primates have diversified in arboreal habitats (trees and bushes) and possess many characteristics that are adaptations to this environment.[44] They are distinguished by:
retention of the collar bone in the pectoral girdle;[44]
shoulder joints which allow high degrees of movement in all directions;[44]
five digits on the fore and hind limbs with opposable thumbs and big toes;[44]
nails on the fingers and toes (in most species);[45]
a flat nail on the hallux (in all extant species);[45]
sensitive tactile pads on the ends of the digits;[44]
orbits encircled in bone;[46]
a trend towards a reduced snout and flattened face, attributed to a reliance on vision at the expense of olfaction (most notably in haplorrhines, and less so in strepsirrhines);[46]
a complex visual system with stereoscopic vision, high visual acuity and color vision;[44]
a brain having a well-developed cerebellum with posterior lobe and a calcarine fissure;[46]
a large brain in comparison to body size, especially in simians;[44]
differentiation of an enlarged cerebral cortex;[44]
reduced number of teeth compared to primitive mammals;[44]
three kinds of teeth;[46]
a well-developed cecum;[46]
two pectoral mammary glands;[44]
typically one young per pregnancy;[44]
a pendulous penis and scrotal testes;[46]
a long gestation and developmental period;[44] and
a trend towards holding the torso upright leading to bipedalism.[44]
Not all primates exhibit these anatomical traits, nor is every trait unique to primates. For example, other mammals have collar bones, three kinds of teeth and a pendulous penis, while spider monkeys have greatly reduced thumbs, ruffed lemurs have six mammary glands and strepsirrhines generally have longer snouts and a strong sense of smell.[46]
In regard to behavior, primates are frequently highly social, with flexible dominance hierarchies.[47] New World species form monogamous pair bonds, and show substantial paternal care of their young, unlike most Old World monkeys.[48]
[edit]Anatomy, physiology, and morphology
Primates have forward-facing eyes on the front of the skull; binocular vision allows accurate distance perception, useful for the brachiating ancestors of all great apes.[44] There is a bony ridge above the eye sockets; this ridge reinforces weaker bones in the face which are put under strain during chewing. Strepsirrhines have a postorbital bar, a bone which runs around the eye socket, to protect their eyes; in contrast, the higher primates, haplorrhines, have evolved fully enclosed sockets.[49]
Primate crania. The labels indicate brain mass.
The primate skull has a large domed cranium which is particularly prominent in anthropoids. The cranium protects the large brain, a distinguishing characteristic of this group.[44] The endocranial volume (the volume within the skull) is three times greater in humans than in the greatest non-human primate, reflecting a larger brain size.[50] The mean endocranial volume is 1201 cubic centimeters in humans, 469 cm3 in gorillas, 400 cm3 in chimpanzees and 397 cm3 in orangutans.[50] The primary evolutionary trend of primates has been the elaboration of the brain, in particular the neocortex (a part of the cerebral cortex), which is involved with sensory perception, generation of motor commands, spatial reasoning, conscious thought and, in humans, language.[4] While other mammals rely heavily on their sense of smell, the arboreal life of primates has led to a tactile, visually dominant sensory system, [4] a reduction in the olfactory region of the brain and increasingly complex social behavior.[51]
An 1893 drawing of the hands and feet of various primates
Primates generally have five digits on each limb (pentadactyly), with keratin nails on the end of each finger. The bottom sides of the hands and feet have sensitive pads on the fingertips. Most have opposable thumbs, a characteristic primate feature; however, opposing thumbs are not limited to this order (opossums, for example, also have them).[44] Thumbs allow some species to use tools. In primates, the combination of opposing thumbs, short fingernails (rather than claws) and long, inward-closing fingers is a relict of the ancestral practice of gripping branches, and has, in part, allowed some species to develop brachiation (swinging by the arms from tree limb to tree limb) as a significant means of transportation. Prosimians have clawlike nails on the second toe of each foot, called toilet-claws, which they use for grooming.[44]
The primate collar bone is retained as prominent element of the pectoral girdle; this allows the shoulder joint broad mobility.[47] Apes have more mobile shoulder joints and arms due to the dorsal position of the scapula, broad ribcages that are flatter front-to-back, and a shorter, less mobile spine compared to Old World monkeys (with lower vertebrae greatly reduced, resulting in tail loss in some species). Old World monkeys are unlike apes in that most have tails. The only primate family with fully prehensile tails are the New World atelids, including the howler, spider, woolly spider and woolly monkeys (New World capuchins have partially prehensile tails).
Primates show an evolutionary trend towards a reduced snout.[47] Technically, Old World monkeys are distinguished from New World monkeys by the structure of the nose, and from apes by the arrangement of their teeth.[51] In New World monkeys the nostrils face sideways; in Old World monkeys, they face downwards.[51] There is a considerably varied dental pattern in primates and although some have lost most of their incisors, all retain at least one lower incisor.[51] In most strepsirhines, the lower incisors and canines form a toothcomb, which is used in grooming and sometimes foraging, [46][51] and the first lower premolar is shaped like a canine.[46] Old World monkeys have eight premolars, compared with twelve in New World monkeys.[51] The Old World species are divided into apes and monkeys depending on the number of cusps on their molars; apes have five, Old World monkeys have four, [51] although humans may have 4 or 5.[52] The main hominid molar cusp (hypocone) evolved in early primate history, while the cusp of the corresponding primitive lower molar (paraconid) was lost. Prosimians are distinguished by their immobilized upper lips, the moist tip of their nose and forward-facing lower front teeth.
The evolution of color vision in primates is unique among most eutherian mammals. While the remote vertebrate ancestors of the primates possessed three color vision (trichromaticism), the nocturnal, warm-blooded, mammalian ancestors lost one of three cones in the retina during the Mesozoic era. Fish, reptiles and birds are therefore trichromatic or tetrachromatic while all mammals, with the exception of some primates and marsupials, [53] are dichromats or monochromats (totally color blind).[46] Nocturnal primates, such as the night monkeys and bush babies, are often monochromatic. Catarrhines are routinely trichromatic due to a gene duplication of the red-green opsin gene at the base of their lineage, 30 to 40 million years ago.[46][54] Platyrrhines, on the other hand, are trichromatic in a few cases only.[55] Specifically, individual females must be heterozygous for two alleles of the opsin gene (red and green) located on the same locus of the X chromosome.[46] Males, therefore, can only be dichromatic, while females can be either dichromatic or trichromatic. Color vision in strepsirrhines is not as well understood; however, research indicates a range of color vision similar to that found in platyrrhines.[46]
Like catarrhines, howler monkeys (a family of platyrrhines) show routine trichromatism that has been traced to an evolutionarily recent gene duplication.[56] Howler monkeys are one of the most specialized leaf-eaters of the New World monkeys; fruits are not a major part of their diet, [57] and the type of leaves they prefer to consume (young, nutritive, and digestible) are detectable only by a red-green signal. Field work exploring the dietary preferences of howler monkeys suggests that routine trichromaticism was environmentally selected for.[55]
[edit]Sexual dimorphism
Main article: Sexual dimorphism in non-human primates
Distinct sexual size dimorphism can be seen between the female and two male Hamadryas baboons.
Sexual dimorphism, the variation between individuals of different sex in the same species, is often exhibited in simians, though to a greater degree in Old World species (apes and some monkeys) than New World species. Recent studies involve comparing DNA to examine both the variation in the expression of the dimorphism among primates and the fundamental causes of sexual dimorphism. Primates usually have dimorphism in body mass[58][59] and canine tooth size[60][61] along with pelage and skin color.[62] The dimorphism can be attributed to and affected by different factors, including mating system, [63] size, [63] habitat and diet.[64]
Comparative analyses have generated a more complete understanding of the relationship between sexual selection, natural selection, and mating systems in primates. Studies have shown that dimorphism is the product of changes in both male and female traits.[65] Ontogenetic scaling, where relative extension of a common growth trajectory occurs, may give some insight into the relationship between sexual dimorphism and growth patterns.[66] Some evidence from the fossil record suggests that there was convergent evolution of dimorphism, and some extinct hominids probably had greater dimorphism than any living primate.[65]
[edit]Locomotion
Diademed sifaka, a lemur species, is a vertical clinger and leaper
Primate species move by brachiation, bipedalism, leaping, arboreal and terrestrial quadrupedalism, climbing, knuckle-walking or by a combination of these methods. Several prosimians are primarily vertical clinger and leapers. These include many bushbabies, all indriids (i.e., sifakas, avahis and indris), sportive lemurs, and all tarsiers.[67] Other prosimians are arboreal quadrupeds and climbers. Some are also terrestrial quadrupeds, while some are leapers. Most monkeys are both arboreal and terrestrial quadrupeds and climbers. Gibbons, muriquis and spider monkeys all brachiate extensively, [30] with gibbons sometimes doing so in remarkably acrobatic fashion. Woolly monkeys also brachiate at times.[57] Orangutans use a similar form of locomotion called quadramanous climbing, in which they use their arms and legs to carry their heavy bodies through the trees.[30] Chimpanzees and gorillas knuckle walk, [30] and can move bipedally for short distances. Although numerous species, such as australopithecines and early hominids, have exhibited fully bipedal locomotion, humans are the only extant species with this trait.
[edit]Behavior
[edit]Social systems
Richard Wrangham stated that social systems of non-human primates are best classified by the amount of movement by females occurring between groups.[68] He proposed four categories:
Female transfer systems – females move away from the group in which they were born. Females of a group will not be closely related whereas males will have remained with their natal groups, and this close association may be influential in social behavior. The groups formed are generally quite small. This organization can be seen in chimpanzees, where the males, who are typically related, will cooperate in defense of the group's territory. Among New World Monkeys, spider monkeys and muriquis use this system.[69]
Japanese macaques bathe together in Jigokudani Hot Springs
Male transfer systems – while the females remain in their natal groups, the males will emigrate as adolescents. Polygynous and multi-male societies are classed in this category. Group sizes are usually larger. This system is common among the ring-tailed lemur, capuchin monkeys and cercopithecine monkeys.[30]
Monogamous species – a male–female bond, sometimes accompanied by a juvenile offspring. There is shared responsibility of parental care and territorial defense. The offspring leaves the parents' territory during adolescence. Gibbons essentially use this system, although "monogamy" in this context does not necessarily mean absolute sexual fidelity.[70]
Solitary species – often males who defend territories that include the home ranges of several females. This type of organization is found in the prosimians such as the slow loris. Orangutans do not defend their territory but effectively have this organization.[71]
Other systems are known to occur as well. For example, with howler monkeys both the males and females typically transfer from their natal group on reaching sexual maturity, resulting in groups in which neither the males nor females are typically related.[57] Some prosimians, colobine monkeys and callitrichid monkeys use this system.[30]
Chimpanzees are social animals.
Primatologist Jane Goodall, who studied in the Gombe Stream National Park, noted fission-fusion societies in chimpanzees.[72] There is fission where the main group splits up to forage during the day, then fusion when the group returns at night to sleep as a group. This social structure can also be observed in the Hamadryas baboon, [73] spider monkeys[57] and the bonobo.[73] The gelada has a similar social structure in which many smaller groups come together to form temporary herds of up to 600 monkeys.[73]
These social systems are affected by three main ecological factors: distribution of resources, group size and predation.[48] Within a social group there is a balance between cooperation and competition. Cooperative behaviors include social grooming (removing skin parasites and cleaning wounds), food sharing, and collective defense against predators or of a territory. Aggressive behaviors often signal competition for availability of food, sleeping sites or mates. Aggression is also used in establishing dominance hierarchies.[48][74]
[edit]Interspecific associations
Several species of primates are known to associate in the wild. Some of these associations have been extensively studied. In the Tai Forest of Africa several species coordinate anti-predator behavior. These include the Diana monkey, Campbell's mona monkey, lesser spot-nosed monkey, western red colobus, king colobus and sooty mangabey, which coordinate anti-predator alarm calls.[75] Among the predators of these monkeys is the common chimpanzee.[76]
The red-tailed monkey associates with several species, including the Western red colobus, blue monkey, Wolf's mona monkey, mantled guereza, black crested mangabey and Allen's swamp monkey.[73] Several of these species are preyed upon by the common chimpanzee.[77]
In South America, squirrel monkeys associate with capuchin monkeys.[78] This may have more to do with foraging benefits to the squirrel monkeys than anti-predation benefits.[78]
[edit]Cognition and communication
Main article: Primate cognition
Further information: Great ape language
Primates have advanced cognitive abilities: some make tools and use them to acquire food and for social displays;[79][80] some have sophisticated hunting strategies requiring cooperation, influence and rank;[81] they are status conscious, manipulative and capable of deception;[82] they can recognise kin and conspecifics;[83][84] and they can learn to use symbols and understand aspects of human language including some relational syntax and concepts of number and numerical sequence.[85][86][87] Research in primate cognition explores problem solving, memory, social interaction, a theory of mind, and numerical, spatial, and abstract concepts.[88] Comparative studies show a trend towards higher intelligence going from prosimians to New World monkeys to Old World monkeys, and significantly higher average cognitive abilities in the great apes.[89][90] However, there is a great deal of variation in each group (e.g., among New World monkeys, both spider[89] and capuchin monkeys[90] have scored highly by some measures), as well as in the results of different studies.[89][90]
Lemurs, lorises, tarsiers, and New World monkeys rely on olfactory signals for many aspects of social and reproductive behavior.[4] Specialized glands are used to mark territories with pheromones, which are detected by the vomeronasal organ; this process forms a large part of the communication behavior of these primates.[4] In Old World monkeys and apes this ability is mostly vestigial, having regressed as trichromatic eyes evolved to become the main sensory organ.[91] Primates also use vocalizations, gestures, and facial expressions to convey psychological state.[92]
[edit]Life history
Primates have slower rates of development than other mammals.[30] All primate infants are breastfed by their mothers (with the exception of some human cultures and various zoo raised primates which are fed formula) and rely on them for grooming and transportation.[30] In some species, infants are protected and transported by males in the group, particularly males who may be their fathers.[30] Other relatives of the infant, such as siblings and aunts, may participate in its care as well.[30] Most primate mothers cease ovulation while breastfeeding an infant; once the infant is weaned the mother can reproduce again.[30] This often leads to weaning conflict with infants who attempt to continue breastfeeding.[30]
Primates have a longer juvenile period between weaning and sexual maturity than other mammals of similar size.[30] During the juvenile period, primates are more susceptible than adults to predation and starvation; they gain experience in feeding and avoiding predators during this time [30] They learn social and fighting skills, often through playing.[30]
Primates, especially females, have longer lifespans than other similarly sized mammals.[30] Late in life, female catarrhine primates appear to undergo a cessation of reproductive function known as menopause; other groups are less studied.[93]
[edit]Diet and feeding
Leaf eating mantled guereza, a species of black-and-white colobus
Foraging crab-eating macaques temporarily store food in their cheek pouches
Primates exploit a variety of food sources. It has been said that many characteristics of modern primates, including humans, derive from an early ancestor's practice of taking most of its food from the tropical canopy.[94] Most primates include fruit in their diets to obtain easily digested carbohydrates and lipids for energy.[30] However, they require other foods, such as leaves or insects, for amino acids, vitamins and minerals. Primates in the suborder Strepsirrhini (non-tarsier prosimians) are able to synthesize vitamin C, like most other mammals, while primates of the suborder Haplorrhini (tarsiers, monkeys and apes) have lost this ability, and require the vitamin in their diet.[95]
Many primates have anatomical specializations that enable them to exploit particular foods, such as fruit, leaves, gum or insects.[30] For example, leaf eaters such as howler monkeys, black-and-white colobuses and sportive lemurs have extended digestive tracts which enable them to absorb nutrients from leaves that can be difficult to digest.[30] Marmosets, which are gum eaters, have strong incisor teeth, enabling them to open tree bark to get to the gum, and claws rather than nails, enabling them to cling to trees while feeding.[30] The aye-aye combines rodent-like teeth with a long, thin middle finger to fill the same ecological niche as a woodpecker. It taps on trees to find insect larvae, then gnaws holes in the wood and inserts its elongated middle finger to pull the larvae out.[96] Some species have additional specializations. For example, the grey-cheeked mangabey has thick enamel on its teeth, enabling it to open hard fruits and seeds that other monkeys cannot.[30]
The gelada is the only primate species that feeds primarily on grass.[97] Tarsiers are the only extant obligate carnivorous primates, exclusively eating insects, crustaceans, small vertebrates and snakes (including venomous species).[98] Capuchin monkeys, on the other hand, can exploit many different types of food, including fruit, leaves, flowers, buds, nectar, seeds, insects and other invertebrates, bird eggs, and small vertebrates such as birds, lizards, squirrels and bats.[57] The common chimpanzee has a varied diet that includes predation on other primate species, such as the western red colobus monkey.[76][77]
[edit]Habitat and distribution
Rhesus macaque at Agra Fort, India
Primates evolved from arboreal animals, and many species live most of their lives in trees. Most primate species live in tropical rain forests. The number of primate species within tropical areas has been shown to be positively correlated to the amount of rainfall and the amount of rain forest area.[99] Accounting for 25% to 40% of the fruit-eating animals (by weight) within tropical rainforests, primates play an important ecological role by dispersing seeds of many tree species.[100]
Some species are partially terrestrial, such as baboons and patas monkeys, and a few species are fully terrestrial, such as geladas and humans. Non-human primates live in a diverse number of forested habitats in the tropical latitudes of Africa, India, Southeast Asia, and South America, including rainforests, mangrove forests, and montane forests. There are some examples of non-human primates that live outside of the tropics; the mountain-dwelling Japanese macaque lives in the north of Honsh? where there is snow-cover eight months of the year; the Barbary macaque lives in the Atlas Mountains of Algeria and Morocco. Primate habitats span a range of altitudes: the black snub-nosed monkey has been found living in the Hengduan Mountains at altitudes of 4, 700 meters (15, 400 ft), [101] the mountain gorilla can be found at 4, 200 meters (13, 200 ft) crossing the Virunga Mountains, [102] and the gelada has been found at elevations of up to 5, 000 metres (16, 000 ft) in the Ethiopian Highlands. Although most species are generally shy of water, a few are good swimmers and are comfortable in swamps and watery areas, including the proboscis monkey, De Brazza's monkey and Allen's swamp monkey, which has developed small webbing between its fingers. Some primates, such as the rhesus macaque and gray langurs, can exploit human-modified environments and even live in cities.[73][103]
[edit]Interactions between humans and other primates
Close interactions between humans and other primates (NHPs) can create pathways for the transmission of zoonotic diseases. Viruses such as Herpesviridae (most notably Herpes B Virus), Poxviridae, measles, ebola, rabies, the Marburg virus and viral hepatitis can be transmitted to humans; in some cases the viruses produce potentially fatal diseases in both humans and non-human primates.[104]
[edit]Legal and social status
Only humans are recognized as persons and protected in law by the United Nations Universal Declaration of Human Rights.[b] The legal status of NHPs, on the other hand, is the subject of much debate, with organizations such as the Great Ape Project (GAP) campaigning to award at least some of them legal rights.[105] In June 2008, Spain became the first country in the world to recognize the rights of some NHPs when its parliament's cross-party environmental committee urged the country to comply with GAP's recommendations, which are that chimpanzees, bonobos, orangutans, and gorillas not be used for animal experiments.[106][107]
Capuchin monkeys' manual dexterity is one reason they can assist quadriplegic humans.
Many species of NHP are kept as pets by humans. GAP estimates that around 3, 000 NHPs live as exotic pets in the United States, while the Humane Society of the United States puts the figure much higher, at around 15, 000.[108] The expanding Chinese middle class has increased demand for NHPs as exotic pets in recent years.[109] Although NHP import for the pet trade was banned in the U.S. in 1975, smuggling still occurs along the United States – Mexico border, with prices ranging from US$3000 for monkeys to $30, 000 for apes.[110]
Primates are used as model organisms in laboratories and have been used in space missions.[111] They serve as service animals for disabled humans. Capuchin monkeys can be trained to assist quadriplegic humans; their intelligence, memory, and manual dexterity make them ideal helpers.[112]
NHPs are kept in zoos around the globe. Historically, zoos were primarily a form of entertainment, but more recently have shifted their focus to conservation, education and research. Many zoos now feature naturalistic exhibits and educational material for the public; in the United States many participate in the Species Survival Plan (SSP), developed by the Association of Zoos and Aquariums (AZA), to maximize genetic diversity through captive breeding. Zoos and other animal welfare supporters generally oppose animal rights initiatives and the GAP's insistence that all NHPs be released from captivity for two primary reasons. First, captive-born primates lack the knowledge and experience to survive in the wild if released. Second, zoos provide living space for primates and other animals threatened with extinction in the wild.
[edit]Role in scientific research
Further information: Animal testing on non-human primates and International trade in primates
Thousands of non-human primates are used around the world in research because of their psychological and physiological similarity to humans.[113][114] In particular, the brains and eyes of NHPs more closely parallel human anatomy than those of any other animals. NHPs are commonly used in preclinical trials, neuroscience, ophthalmology studies, and toxicity studies. Rhesus macaques are often used, as are other macaques, African green monkeys, chimpanzees, baboons, squirrel monkeys, and marmosets, both wild-caught and purpose-bred.[113][115] In 2005, GAP reported that 1, 280 of the 3, 100 NHPs living in captivity in the United States were used for experiments.[105] In 2004, the European Union used around 10, 000 NHPs in such experiments; in 2005 in Great Britain, 4, 652 experiments were conducted on 3, 115 NHPs.[116] Governments of many nations have strict care requirements of NHPs kept in captivity. In the US, federal guidelines extensively regulate aspects of NHP housing, feeding, enrichment, and breeding.[117] European groups such as the European Coalition to End Animal Experiments are seeking a ban on all NHP use in experiments as part of the European Union's review of animal testing legislation.[118]
[edit]Conservation
The International Union for Conservation of Nature (IUCN) lists more than a third of primates as critically endangered or vulnerable. Trade is regulated, as all species are listed by CITES in Appendix II, except 50 species and subspecies listed in Appendix I, which gain full protection from trade.[119][120] Common threats to primate species include deforestation, forest fragmentation, monkey drives (resulting from primate crop raiding), [121] and primate hunting for use in medicines, as pets, and for food. Large-scale tropical forest clearing is widely regarded as the process that most threatens primates.[122][123][124] More than 90% of primate species occur in tropical forests.[123][125] The main cause of forest loss is clearing for agriculture, although commercial logging, subsistence harvesting of timber, mining, and dam construction also contribute to tropical forest destruction.[125] In Indonesia large areas of lowland forest have been cleared to increase palm oil production, and one analysis of satellite imagery concluded that during 1998 and 1999 there was a loss of 1, 000 Sumatran orangutans per year in the Leuser Ecosystem alone.[126]
The critically endangered Sumatran orangutan
Primates with a large body size (over 5 kg) are at increased extinction risk due to their greater profitability to poachers compared to smaller primates.[125] They reach sexual maturity later and have a longer period between births. Populations therefore recover more slowly after being depleted by poaching or the pet trade.[127] Data for some African cities show that half of all protein consumed in urban areas comes from the bushmeat trade.[128] Endangered primates such as guenons and the drill are hunted at levels that far exceed sustainable levels.[128] This is due to their large body size, ease of transport and profitability per animal.[128] As farming encroaches on forest habitats, primates feed on the crops, causing the farmers large economic losses.[129] Primate crop raiding gives locals a negative impression of primates, hindering conservation efforts.[130]
Madagascar, home to five endemic primate families, has experienced the greatest extinction of the recent past; since human settlement 1, 500 years ago, at least eight classes and fifteen of the larger species have become extinct due to hunting and habitat destruction.[4] Among the primates wiped out were Archaeoindris (a lemur larger than a silverback gorilla) and the families Palaeopropithecidae and Archaeolemuridae.[4]
In Asia, Hinduism, Buddhism, and Islam prohibit eating primate meat; however, primates are still hunted for food.[125] Some smaller traditional religions allow the consumption of primate meat.[131][132] The pet trade and traditional medicine also increase demand for illegal hunting.[109][133][134] The rhesus macaque, a model organism, was protected after excessive trapping threatened its numbers in the 1960s; the program was so effective that they are now viewed as a pest throughout their range.[124]
The critically endangered Cross River gorilla
In Central and South America forest fragmentation and hunting are the two main problems for primates. Large tracts of forest are now rare in Central America.[122][135] This increases the amount of forest vulnerable to edge effects such as farmland encroachment, lower levels of humidity and a change in plant life.[136][137] Movement restriction results in a greater amount of inbreeding, which can cause deleterious effects leading to a population bottleneck, whereby a significant percentage of the population is lost.[138][139]
There are 21 critically endangered primates, 7 of which have remained on the IUCN's "The World's 25 Most Endangered Primates" list since the year 2000: the silky sifaka, Delacour's langur, the white-headed langur, the gray-shanked douc, the Tonkin snub-nosed monkey, the Cross River gorilla and the Sumatran orangutan.[140] Miss Waldron's red colobus was recently declared extinct when no trace of the subspecies could be found from 1993 to 1999.[141] A few hunters have found and killed individuals since then, but the subspecies' prospects remain bleak.[142] |
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Lemurs (pronounced /?li?m?(r)/ US dict: l??·m?r) are a clade of strepsirrhine primates endemic to the island of Madagascar. They are named after the lemures (ghosts or spirits) of Roman mythology due to the ghostly vocalizations, reflective eyes, and the nocturnal habits of some species. Although lemurs often are confused with ancestral primates, the anthropoid primates (monkeys, apes, and humans) did not evolve from them; instead, lemurs merely share morphological and behavioral traits with basal primates. Lemurs arrived in Madagascar around 62 to 65 mya by rafting on mats of vegetation at a time when ocean currents favored oceanic dispersal to the island. Since that time, lemurs have evolved to cope with an extremely seasonal environment and their adaptations give them a level of diversity that rivals that of all other primate groups. Until shortly after humans arrived on the island around 2, 000 years ago, there were lemurs as large as a male gorilla. Today, there are nearly 100 species of lemurs, and most of those species have been discovered or promoted to full species status since the 1990s; however, lemur taxonomic classification is controversial and depends on which species concept is used. Even the higher-level taxonomy is disputed, with some experts preferring to place most lemurs within the infraorder Lemuriformes, while others prefer Lemuriformes to contain all living strepsirrhines, placing all lemurs in superfamily Lemuroidea and all lorises and galagos in superfamily Lorisoidea.
Ranging in size from 30 g (1.1 oz) to 9 kg (20 lb), lemurs share many common, basal primate traits, such as divergent digits on their hands and feet and nails instead of claws (in most species). However, their brain-to-body size ratio is smaller than that of anthropoid primates, and among many other traits they share with other strepsirrhine primates, they have a "wet nose" (rhinarium). Lemurs are generally the most social of the strepsirrhine primates and communicate more with scents and vocalizations than with visual signals. Many lemur adaptations are in response to Madagascar's highly seasonal environment. Lemurs have relatively low basal metabolic rates and may exhibit seasonal breeding, dormancy (such as hibernation or torpor), or female social dominance. Most eat a wide variety of fruits and leaves, while some are specialists. Although many share similar diets, different species of lemur share the same forests by differentiating niches.
Lemur research focused on taxonomy and specimen collection during the 18th and 19th centuries. Although field observations trickled in from early explorers, modern studies of lemur ecology and behavior did not begin in earnest until the 1950s and 1960s. Initially hindered by political instability and turmoil on Madagascar during the mid-1970s, field studies resumed in the 1980s and have greatly increased our understanding of these primates. Research facilities like the Duke Lemur Center have provided research opportunities under more controlled settings. Lemurs are important for research because their mix of primitive characteristics and traits shared with anthropoid primates can yield insights on primate and human evolution. However, many lemur species are threatened with extinction due to habitat loss and hunting. Although local traditions generally help protect lemurs and their forests, illegal logging, widespread poverty, and political instability hinder and undermine conservation efforts.
Contents [hide]
1 Etymology
2 Evolutionary history
2.1 Distribution and diversity
2.2 Taxonomic classification and phylogeny
3 Anatomy and physiology
3.1 Dentition
3.2 Senses
3.3 Metabolism
4 Behavior
4.1 Diet
4.2 Social systems
4.3 Activity patterns
4.4 Locomotion
4.5 Communication
4.6 Predator avoidance
4.7 Reproduction
4.8 Cognitive abilities and tool use
5 Ecology
6 Research
7 Conservation
7.1 Threats in the wild
7.2 Conservation efforts
8 Cultural references
9 Footnotes
10 References
10.1 Books cited
11 External links
[edit]Etymology
Carl Linnaeus, the founder of modern binomial nomenclature, gave lemurs their name as early as 1758, when he used it in 10th edition of Systema Naturae. He included three species under the genus Lemur: Lemur tardigradus (the red slender loris, now known as Loris tardigradus), Lemur catta (the ring-tailed lemur), and Lemur volans (the Philippine colugo, now known as Cynocephalus volans).[2] Although the term "lemur" was apparently at first intended for lorises, it was soon limited to the endemic Malagasy primates, which have been known as "lemurs" ever since.[3] The name derives from the Latin term lemures, [4] which refers to specters or ghosts that were exorcised during the Lemuria festival.[5] Linnaeus was familiar with the nocturnal habits and ghost-like appearance of lemurs and lorises, [6] as well as their noiseless movements at night, reflective eyes, and ghostly cries. He may also have known that the some Malagasy people have held legends that lemurs are the souls of their ancestors.[7] Being familiar with the works of Virgil and Ovid and seeing an analogy that fit with his naming scheme, Linnaeus adapted the term "lemur" for these nocturnal primates.[8]
[edit]Evolutionary history
Main article: Evolutionary history of lemurs
Lemurs are prosimian primates belonging to the suborder Strepsirrhini. Like other strepsirrhine primates, such as lorises, pottos, and galagos, they share ancestral (or plesiomorphic) traits with early primates. In this regard, lemurs are popularly confused with ancestral primates; however, lemurs did not give rise to monkeys and apes (simians). Instead, they evolved independently in isolation on Madagascar.[9] All modern strepsirrhines including lemurs are traditionally thought to have evolved from primitive primates known as adapiforms during the Eocene (56 to 34 mya) or Paleocene (65 to 56 mya).[9][10][11] Adapiforms, however, lack a specialized arrangement of teeth, known as a toothcomb, which nearly all living strepsirrhines possess.[12][13][14] A more recent hypothesis is that lemurs descended from lorisiform (loris-like) primates. This is supported by comparative studies of the cytochrome b gene and the presence of the strepsirrhine toothcomb in both groups.[14][15] Instead of being the direct ancestors of lemurs, the adapiforms may have given rise to both the lemurs and lorisiforms, a split that would be supported by molecular phylogenetic studies.[14] The later split between lemurs and lorises is thought to have occurred approximately 62 to 65 mya according to molecular studies, [16] although other genetic tests and the fossil record in Africa suggest more conservative estimates of 50 to 55 mya for this divergence.[17]
A reconstructed map of the Earth during the Early Paleocene, approximately 65 million years ago, around the time that lemurs first evolved and colonized Madagascar
Once part of the supercontinent Gondwana, the island of Madagascar has been isolated since it broke away from eastern Africa (~160 mya), Antarctica (~80–130 mya), and India (~80–90 mya).[18][19] Since ancestral lemurs are thought to have originated in Africa around 62 to 65 mya, they would have had to have crossed the Mozambique Channel, a deep channel between Africa and Madagascar with a minimum width of about 560 km (350 mi).[14] In 1915, paleontologist William Diller Matthew noted that the mammalian biodiversity on Madagascar (including lemurs) can only be accounted for by random rafting events, where very small populations rafted from nearby Africa on tangled mats of vegetation, which get flushed out to sea from major rivers.[20] This form of biological dispersal can occur randomly over millions of years.[14][21] In the 1940s, American paleontologist George Gaylord Simpson coined the term "sweepstakes hypothesis" for such random events.[22] Rafting has since been the most accepted explanation for the lemur colonization of Madagascar, [23][24] but until recently this trip was thought to be very unlikely because strong ocean currents flow away from the island.[25] In January 2010, a report demonstrated that around 60 mya both Madagascar and Africa were 1, 650 km (1, 030 mi) south of their present-day positions, placing them in a different ocean gyre, producing currents that ran counter to what they are today. The ocean currents were shown to be even stronger than today, which would have pushed a raft along faster, shortening the trip to 30 days or less—short enough for a small mammal to survive easily. As the continental plates drifted northward, the currents gradually changed, and by 20 mya the window for oceanic dispersal had closed, effectively isolating the lemurs and the rest of the terrestrial Malagasy fauna from mainland Africa.[25] Isolated on Madagascar with only a limited number of mammalian competitors, the lemurs did not have to compete with other evolving arboreal mammalian groups, such as squirrels.[26] They were also spared from having to compete with monkeys, which evolved later. The intelligence, aggression, and deceptiveness of monkeys gave them an advantage over other primates in exploiting the environment.[4][13]
[edit]Distribution and diversity
See also: Subfossil lemur
A life restoration of Babakotia radofilai, a sloth lemur that became extinct less than two thousand years ago
Lemurs have adapted to fill many open ecological niches since making their way to Madagascar.[13][26] Their diversity in both behavior and morphology (outward appearance) rivals that of the monkeys and apes found elsewhere in the world.[4] Ranging in size from the 30 g (1.1 oz) Madame Berthe's mouse lemur, the world's smallest primate, [27] to the recently extinct 160–200 kg (350–440 lb) Archaeoindris fontoynonti, [28] lemurs evolved diverse forms of locomotion, varying levels of social complexity, and unique adaptations to the local climate.[13][29]
Lemurs lack any shared traits that make them stand out from all other primates.[30] Different types of lemurs have evolved unique combinations of unusual traits to cope with Madagascar's harsh, seasonal climate. These traits can include seasonal fat storage, hypometabolism (including torpor and hibernation), small group sizes, low encephalization (relative brain size), cathemerality (activity both day and night), and strict breeding seasons.[10][29] Extreme resource limitations and seasonal breeding are also thought to have given rise to three other relatively common lemur traits: female social dominance, sexual monomorphism, and male–male competition for mates involving low levels of agonism, such as sperm competition.[31]
Before the arrival of humans roughly 1500 to 2000 years ago, lemurs were found all across the island.[26] However, early settlers quickly converted the forests to rice paddies and grassland through slash-and-burn agriculture (known locally as tavy), restricting lemurs to approximately 10% of the island's area, ~60, 000 km2 (23, 000 sq mi).[32] Today, the diversity and complexity of lemur communities increases with floral diversity and precipitation and is highest in the rainforests of the east coast, where precipitation and floral diversity are also at their highest.[11] Despite their adaptations for weathering extreme adversity, habitat destruction and hunting have resulted in lemur populations declining sharply, and their diversity has diminished, with the recent extinction of at least 17 species in eight genera, [26][28][33] known collectively as the subfossil lemurs. Most of the approximately 100 species and subspecies of lemur are either threatened or endangered. Unless trends change, extinctions are likely to continue.[34]
Until recently, giant lemurs existed on Madagascar. Now represented only by recent or subfossil remains, they were modern forms that were once part of the rich lemur diversity that has evolved in isolation. Some of their adaptations were unlike those seen in their living relatives.[26]All 17 extinct lemurs were larger than the extant (living) forms, some weighing as much as 200 kg (440 lb), [4] and are thought to have been active during the day.[35] Not only were they unlike the living lemurs in both size and appearance, they also filled ecological niches that either no longer exist or are now left unoccupied.[26] Large parts of Madagascar, which are now devoid of forests and lemurs, once hosted diverse primate communities that included more than 20 lemur species covering the full range of lemur sizes.[36]
[edit]Taxonomic classification and phylogeny
Lemur phylogeny[23][37][36]
Strepsirrhini
Lorisiform clade
Galagidae (galagos)
Lorisidae (lorises)
Lemur clade
Daubentonia (aye-aye)
Lemuridae (brown lemurs and allies)
†Megaladapidae (koala lemurs)
Lepilemuridae (sportive lemurs)
Cheirogaleidae (mouse lemurs and allies)
†Archaeolemuridae (monkey lemurs)
†Palaeopropithecidae (sloth lemurs)
Indriidae (sifakas, indris, and woolly lemurs)
Main article: Taxonomy of lemurs
For a more comprehensive list, see List of lemur species.
From a taxonomic standpoint, the term "lemur" originally referred to the genus Lemur, which currently contains only the ring-tailed lemur. The term is now used in the colloquial sense in reference to all Malagasy primates.[38]
Lemur taxonomy is controversial, and not all experts agree, particularly with the recent increase in the number of recognized species.[30][39][40] According to Russell Mittermeier, the president of Conservation International (CI), taxonomist Colin Groves, and others, there are nearly 100 recognized species or subspecies of extant (or living) lemur, divided into five families and 15 genera.[41] Because genetic data indicates that the recently extinct subfossil lemurs were closely related to living lemurs, [42] an additional three families, eight genera, and 17 species can be included in the total.[28][33] In contrast, other experts have labeled this as taxonomic inflation, [40] instead preferring a total closer to 50 species.[30]
The classification of lemurs within the suborder Strepsirrhini is equally controversial, although the most experts agree on the same phylogenetic tree. In one taxonomy published by Colin Groves, the aye-aye was placed in its own infraorder, Chiromyiformes, while the rest of the lemurs were placed in Lemuriformes.[43] In another taxonomy, Lemuriformes contains all living strepsirrhines in two superfamilies, Lemuroidea for all lemurs and Lorisoidea for lorises and galagos.[17]
3 infraorders, 2 superfamilies[43] 1 infraorder, 2 superfamilies[17][44]
Order Primates
Suborder Strepsirrhini: non-tarsier prosimians
Infraorder Chiromyiformes: aye-aye
Infraorder Lemuriformes
Superfamily Cheirogaleoidea
Family Cheirogaleidae: dwarf and mouse lemurs
Superfamily Lemuroidea
Family †Archaeolemuridae: monkey or baboon lemurs
Family Indriidae: woolly lemurs, sifakas, and allies
Family Lemuridae: brown lemurs and allies
Family Lepilemuridae: sportive lemurs
Family †Megaladapidae: koala lemurs
Family †Palaeopropithecidae: sloth lemurs
Infraorder Lorisiformes: galagos and lorises
Suborder Haplorrhini: tarsiers, monkeys and apes
Order Primates
Suborder Strepsirrhini: non-tarsier prosimians
Infraorder Lemuriformes
Superfamily Lemuroidea
Family †Archaeolemuridae: monkey or baboon lemurs
Family Cheirogaleidae: dwarf and mouse lemurs
Family Daubentoniidae: aye-aye
Family Indriidae: woolly lemurs, sifakas, and allies
Family Lemuridae: brown lemurs and allies
Family Lepilemuridae: sportive lemurs
Family †Megaladapidae: koala lemurs
Family †Palaeopropithecidae: sloth lemurs
Superfamily Lorisoidea: galagos and lorises
Suborder Haplorrhini: tarsiers, monkeys and apes
The Sahamalaza sportive lemur (Lepilemur sahamalazensis) was identified as a distinct species in 2006.
Lemur taxonomy has changed significantly since the first taxonomic classification of lemurs by Carl Linnaeus in 1758. One of the greatest challenges has been the classification of the aye-aye, which has been a topic of debate up until very recently.[4] Until Richard Owen published a definitive anatomical study in 1866, early naturalists were uncertain whether the aye-aye (genus Daubentonia) was a primate, rodent, or marsupial.[45][46][47] However, the placement of the aye-aye within the order Primates remained problematic until very recently. Based on its anatomy, researchers have found support for classifying the genus Daubentonia as a specialized indriid, a sister group to all strepsirrhines, and as an indeterminate taxon within the order Primates.[15] Molecular tests have now shown Daubentoniidae is basal to all Lemuriformes, [15][48] and in 2008, Russell Mittermeier, Colin Groves, and others ignored addressing higher-level taxonomy by defining lemurs as monophyletic and containing five living families, including Daubentoniidae.[41]
Relationships among lemur families have also proven to be problematic and have yet to be definitively resolved.[15] To further complicate the issue, several Paleogene fossil primates from outside Madagascar, such as Bugtilemur, have been classified as lemurs.[49] However, scientific consensus does not accept these assignments based on genetic evidence, [15][48] and therefore it is generally accepted that the Malagasy primates are monophyletic.[15][23][37] Another area of contention is the relationship between the sportive lemurs and the extinct koala lemurs (Megaladapidae). Formerly grouped in the same family due to similarities in dentition, [50] they are no longer considered to be closely related due to genetic studies.[37][51]
More taxonomic changes have occurred at the genus level, although these revisions have proven more conclusive, often supported by genetic and molecular analysis. The most noticeable revisions included the gradual split of a broadly defined genus Lemur into separate genera for the ring-tailed lemur, ruffed lemurs, and brown lemurs due to a host of morphological differences.[52][53]
Due to several taxonomic revisions by Russell Mittermeier, Colin Groves, and others, the number of recognized lemur species has grown from 33 species and subspecies in 1994 to approximately 100 in 2008.[30][41][54] With continuing cytogenetic and molecular genetic research, as well as ongoing field studies, particularly with cryptic species such as mouse lemurs, the number of recognized lemur species is likely to keep growing.[30] However, the rapid increase in the number of recognized species has had its critics among taxonomists and lemur researchers. Since classifications ultimately depend on the species concept used, conservationists often favor definitions that result in the splitting of genetically distinct populations into separate species to gain added environmental protection. Others favor a more thorough analysis.[30][40]
[edit]Anatomy and physiology
Lemurs vary greatly in size. They include the smallest primates in the world and, until recently, also included some of the largest. They currently range in size from about 30 g (1.1 oz) for Madame Berthe's mouse lemur (Microcebus berthae) up to 7–9 kg (15–20 lb) for the indri (Indri indri) and diademed sifaka (Propithecus diadema).[55][56] When recently extinct species are considered, the size range extended up to that of a gorilla at 160–200 kg (350–440 lb) for Archaeoindris fontoynonti.[4][28]
Close-up of a ruffed lemur's foot, showing the toilet-claw on the second toe and nails on all other toes
Like all primates, lemurs have five divergent digits with nails (in most cases) on their hands and feet. Most lemurs possess a laterally compressed, elongated nail, called a toilet-claw, on the second toe and use it for scratching and grooming.[46][57] In addition to the toilet-claw, lemurs share a variety of other traits with other strepsirrhine primates, which include a rhinarium (or "wet nose"); a fully functional vomeronasal organ, which detects pheromones; a postorbital bar and the lack of postorbital closure (a wall of thin bone behind the eye); orbits (bony sockets that enclose the eye) that are not fully facing forward; left and right mandible (lower jaw) bones that are not fully fused; and a small brain-to-body mass ratio.[14][58]
Additional traits shared with other prosimian primates (strepsirrhine primates and tarsiers) include a bicornuate (two-horned) uterus and epitheliochorial placentation.[12][58] Because their thumbs are only pseudo-opposable, making their movement less independent of the other fingers, [57] their hands are less than perfect at grasping and manipulating objects.[19] On their feet, they have a widely abducted hallux (first toe) which facilitates the grasping of tree limbs.[46] A common misconception is that lemurs have a prehensile tail, a trait found only in New World monkeys, particularly atelids, among primates.[57] Lemurs also rely heavily on their sense of smell, a trait shared with most other mammals and primitive primates, but not with the visually oriented higher primates.[19]
Lemurs are a diverse group of primates in terms of morphology and physiology.[30] Some lemurs, such as the sportive lemurs and indriids, have longer hind limbs than forelimbs, making them excellent leapers.[59][60][61] Indriids also have a specialized digestive system for folivory, exhibiting enlarged salivary glands, a spacious stomach, and an elongated caecum (lower gut) that facilitates fermentation.[11][13][56][62][63] The hairy-eared dwarf lemur (Allocebus trichotis) reportedly has a very long tongue, allowing it to feed on nectar.[46] Likewise, the red-bellied lemur (Eulemur rubriventer) has a feathery brush-shaped tongue, also uniquely adapted to feed on nectar and pollen.[11] The aye-aye has evolved some traits that are unique among primates, making it stand out among the lemurs. Such traits include continuously growing, rodent-like front teeth for gnawing through wood and hard seeds; a highly mobile, filiform (filament-shaped) middle finger for extracting food from tiny holes; large, bat-like ears for detecting hollow spaces within trees;[13][26][46][64] and use of self-generated acoustical cues to forage.[45]
Lemurs are unusual since they have great variability in their social structure, yet generally lack sexual dimorphism in size and canine tooth morphology.[11][38] However, some species tend towards having larger females, [45] and two species of true lemur (genus Eulemur), the gray-headed lemur (E. albocollaris) and the Red Lemur (E. rufus), exhibit size differences in canine teeth.[65] True lemurs show sexual dichromatism (sexual differences in fur coloration), [38] but the difference between the genders varies from strikingly obvious, as in the black lemur (E. macaco), to nearly imperceptible in the case of the common brown lemur (E. fulvus).[65]
Crypsis, or the inability of humans to visually distinguish between two or more distinct species, has recently been discovered among lemurs, particularly within the sportive lemurs (Lepilemur) and mouse lemurs (Microcebus). With sportive lemurs, subspecies were traditionally defined based on slight morphological differences, but new genetic evidence has supported giving full species status to these regional populations.[51] In the case of mouse lemurs, the gray mouse lemur (M. murinus), golden-brown mouse lemur (M. ravelobensis), and Goodman's mouse lemur (M. lehilahytsara) were considered the same species until recently, when genetic tests identified them as cryptic species.[66]
[edit]Dentition
Lemur deciduous and permanent dentitions
Family Deciduous dental formula[50][67] Permanent dental formula[38][46][68][69]
Cheirogaleidae, Lemuridae
Lepilemuridae
†Archaeolemuridae
†Megaladapidae
Indriidae, †Palaeopropithecidae [N 1] [N 2]
Daubentoniidae
The lemur dentition is heterodont (having multiple tooth morphologies) and derives from an ancestral primate permanent dentition of . Indriids, sportive lemurs, the aye-aye, and the extinct sloth lemurs, monkey lemurs, and koala lemurs have reduced dentitions, having lost incisors, canines, or premolars.[71] The ancestral deciduous dentition is, but young indriids, aye-ayes, koala lemurs, sloth lemurs, and probably monkey lemurs have fewer deciduous teeth.[50][67]
There are also noticeable differences in dental morphology and tooth topography between lemurs. Indri, for instance, have teeth that are perfectly adapted for shearing leaves and crushing seeds.[56] In the toothcomb of most lemurs, the bottom incisors and canine teeth are procumbent (face forward rather than up) and finely spaced, thus providing a tool for either grooming or feeding.[14][50][71] For instance, indri use their toothcomb not only for grooming, but also to pry out the large seeds from the tough exocarp of Beilschmiedia fruits, [72] while fork-marked lemurs use their relatively long toothcomb to cut through tree bark to induce the flow of tree sap.[46] Only the aye-aye, the extinct giant aye-aye, and the largest of the extinct giant sloth lemurs lack a functional strepsirrhine toothcomb.[71][69] In the case of the aye-aye, the morphology of the deciduous incisors, which are lost shortly after birth, indicate that its ancestors had a toothcomb. These milk teeth are lost shortly after birth[73] and are replaced by open-rooted, continually growing (hypselodont) incisors.[71]
A six-tooth version of the strepsirrhine toothcomb in a ring-tailed lemur, with canine-like premolars behind it
The toothcomb in lemurs normally consists of six teeth (four incisors and two canines), although indriids, monkey lemurs, and some sloth lemurs only have a four-tooth toothcomb due to the loss of either a canine or an incisor.[14][71] Because the lower canine is either included in the toothcomb or lost, the lower dentition can be difficult to read, especially since the first premolar (P2) is often shaped like a canine (caniniform) to fill the canine's role.[50] In folivorous (leaf-eating) lemurs, except for indriids, the upper incisors are greatly reduced or absent.[50][71] Used together with the toothcomb on the mandible (lower jaw), this complex is reminiscent of an ungulate browsing pad.[71]
Lemurs are unusual among primates for their rapid dental development, particularly among the largest species. For example, indriids have relatively slow body growth but extremely fast tooth formation and eruption.[74] By contrast, anthropoid primates exhibit slower dental development with increased size and slower morphological development.[71] Lemurs are also dentally precocious at birth, and have their full permanent dentition at weaning.[29]
Lemurs generally have thin tooth enamel compared to anthropoid primates. This may result in extra wear and breakage to the anterior (front) teeth due to heavy use in grooming, feeding, and fighting. Little other dental health information is available for lemurs, except that wild Ring-tailed Lemurs at Berenty Private Reserve occasionally exhibit abscessed maxillary canines (seen as open wounds on the muzzle) and tooth decay, possibly due to the consumption of non-native foods.[71]
[edit]Senses
The sense of smell, or olfaction, is highly important to lemurs and is frequently used in communication.[11][13][19] Lemurs have long snouts (compared to the short snouts of haplorrhines) that are traditionally thought to position the nose for better sifting of smells, [13] although long snouts do not necessarily translate into high olfactory acuity since its not the relative size of the nasal cavity that correlates with smell, but the density of olfactory receptors.[75][76] Instead, the long snouts may facilitate better chewing.[76]
Lemurs generally have a wet nose, or rhinarium, as well as a longer snout than anthropoid primates.
The wet nose, or rhinarium, is a trait shared with other strepsirrhines and many other mammals, but not with haplorrhine primates.[46] Although it is claimed to enhance the sense of smell, [58] it is actually a touch-based sense organ that connects with a well-developed vomeronasal organ (VNO). Since pheromones are usually large, non-volatile molecules, the rhinarium is used to touch a scent-marked object and transfer the pheromone molecules down the philtrum (the nasal mid-line cleft) to the VNO via the nasopalatine ducts that travel through the incisive foramen of the hard palate.[12]
To communicate with smell, which is useful at night, lemurs will scent mark with urine as well as scent glands located on the wrists, inside elbow, genital regions, or the neck.[12][58] The scrotal skin of most male lemurs has scent glands.[77] Ruffed lemurs (genus Varecia) and male sifakas have a gland at the base of their neck, [12][46] while the greater bamboo lemur (Prolemur simus) and the Ring-tailed Lemur have glands inside the upper arms near the axilla.[12] Male ring-tailed lemurs also have scent glands on the inside of their forearms, adjacent to a thorn-like spur, which they use to gouge, and simultaneously, scent-mark tree branches.[46] They will also wipe their tails between their forearms and then engage in "stink fights" by waving their tail as their opponents.[12]
Lemurs (and strepsirrhines in general) are considered to be less visually oriented than the higher primates, since they rely so heavily on their sense of smell and pheromone detection. The fovea on the retina; which yields higher visual acuity, is not well-developed. The postorbital septum (or bony closure behind the eye) in haplorrhine primates is thought to stabilize the eye slightly, allowing for the evolution of the fovea. With only a postorbital bar, lemurs have been unable to develop a fovea.[78] Therefore, regardless of their activity pattern (nocturnal, cathemeral, or diurnal), lemurs exhibit low visual acuity and high retinal summation.[29] Lemurs can see a wider visual field, however, than anthropoid primates due to a slight difference in the angle between the eyes, as shown in the following table:[79]
Optical angles and visual fields[79]
Angle between eyes Binocular field Combined field
(binocular + periphery)
Lemurs 10–15° 114–130° 250–280°
Anthropoid primates 0° 140–160° 180–190°
Although they lack a fovea, some diurnal lemurs have a cone-rich, although less clustered, area centralis.[78] This area centralis has a high rod-to-cone cell ratio in many diurnal species studied thus far, whereas diurnal anthropoids have no rod cells in their fovea. Once again, this suggests lower visual acuity in lemurs than in anthropoids.[80] Furthermore, the rod-to-cone cell ratio can be variable even among diurnal species. For instance, Verreaux's sifaka (Propithecus verreauxi) and the indri (Indri indri) have only a few large cones scattered along their predominantly rod-dominated retina. The eyes of the Ring-tailed Lemur contain one cone to five rods. Nocturnal lemurs such as mouse lemurs and dwarf lemurs, on the other hand, have retinas made up entirely of rod cells.[12]
Since cone cells make color vision possible, the high prevalence of rod cells in lemur eyes suggest they have not evolved color vision.[12] The most studied lemur, the Ring-tailed Lemur, has been shown to have blue-yellow vision, but lacks the ability to distinguish red and green hues.[81] Due to polymorphism in opsin genes, which code for color receptivity, trichromatic vision may rarely occur in females of a few lemur species, such as Coquerel's sifaka (Propithecus coquereli) and the red ruffed lemur (Varecia rubra). Most lemurs, therefore, are either monochromats or dichromats.[12]
Aye-ayes exhibit eyeshine because they have a reflective layer of tissue in the eye, called a tapetum lucidum.
Most lemurs have retained the tapetum lucidum, a reflective layer of tissue in the eye, which is found in many vertebrates.[38] This trait is absent in haplorrhine primates, and its presence further limits the visual acuity in lemurs.[29][80] The strepsirrhine choroidal tapetum is unique among mammals because it is made up of crystalline riboflavin, and the resulting optical scattering is what limits visual acuity.[80] Although the tapetum is considered to be ubiquitous in lemurs, there appear to be exceptions among true lemurs, such as the Black Lemur and the common brown lemur, as well as the ruffed lemurs.[12][29][80] Since the riboflavins in the tapetum have a tendency to dissolve and vanish when processed for histological investigation, however, the exceptions are still debatable.[12]
[edit]Metabolism
Lemurs have low basal metabolic rates (BMR), which helps them to conserve energy during the dry season, when water and food are scarce.[11][61] They can optimize their energy use by lowering their metabolic rate to 20% below the values predicted for mammals of similar body mass.[82] The red-tailed sportive lemur (Lepilemur ruficaudatus), for instance, reportedly has one of the lowest metabolic rates among mammals. Its low metabolic rate may be linked to its generally folivorous diet and relatively small body mass.[61] Lemurs exhibit behavioral adaptations to complement this trait, including sunning behaviors, hunched sitting, group huddling, and nest sharing, in order to reduce heat loss and conserve energy.[82] Dwarf lemurs and mouse lemurs exhibit seasonal cycles of dormancy to conserve energy.[82] Before dry season, they will accumulate fat in white adipose tissue located at the base of the tail and hind legs, doubling their weight.[27][83][84] At the end of the dry season, their body mass may fall to half of what it was prior to the dry season.[27] Lemurs that do not experience states of dormancy are also able to shut down aspects of their metabolism for energy conservation.[82]
[edit]Behavior
Lemur behavior is as variable as lemur morphology. Differences in diet, social systems, activity patterns, locomotion, communication, predator avoidance tactics, breeding systems, and intelligence levels help define lemur taxa and set individual species apart from the rest. Although trends frequently distinguish the smaller, nocturnal lemurs from the larger, diurnal lemurs, there are often exceptions that help exemplify the unique and diverse nature of these Malagasy primates.
[edit]Diet
Mouse lemurs primarily eat fruit, although their diet also includes insects.
Lemur diets are highly variable and demonstrate a high degree of plasticity, [85] although general trends suggest that the smallest species primarily consume fruit and insects (omnivory), while the larger species are more herbivorous, consuming mostly plant material.[35] As with all primates, hungry lemurs might eat anything that is edible, whether or not the item is one of their preferred foods.[12] For instance, the Ring-tailed Lemur eats insects and small vertebrates when necessary[35][52] and as a result it is commonly viewed as an opportunistic omnivore.[71] Coquerel's giant mouse lemur (Mirza coquereli) is mostly frugivorous, but will consume insect secretions during the dry season.[35]
A common assumption in mammalogy is that small mammals cannot subsist entirely on plant material and must have a high-calorie diet in order to survive. As a result, it was thought that the diet of tiny primates must be high in protein-containing insects (insectivory). Research has shown, however, that mouse lemurs, the smallest living primates, consume more fruit than insects, contradicting the popular hypothesis.[12][35]
Plant material makes up the majority of most lemur diets. Members of at least 109 of all known plant families in Madagascar (55%) are exploited by lemurs. Since lemurs are primarily arboreal, most of these exploited species are woody plants, including trees, shrubs, or lianas. Only the ring-tailed lemur, the bamboo lemurs (genus Hapalemur), and the black-and-white ruffed lemur (Varecia variegata) are known to consume herbs. While Madagascar is rich in fern diversity, these plants are rarely eaten by lemurs. One possible reason for this is that ferns lack flowers, fruits, and seeds—common food items in lemur diets. They also occur close to the ground, while lemurs spend most of their time in the trees. Lastly, ferns have an unpleasant taste due to the high content of tannins in their fronds. Likewise, mangroves appear to be rarely exploited by lemurs due to their high tannin content.[85] Some lemurs appear to have evolved responses against common plant defenses, however, such as tannins and alkaloids.[72] The golden bamboo lemur (Hapalemur aureus), for instance, eats giant bamboo (Cathariostachys madagascariensis), which contains high levels of cyanide. This lemur can consume twelve times the typically lethal dose for most mammals on a daily basis; the physiological mechanisms that protect it from cyanide poisoning are unknown.[11] At the Duke Lemur Center (DLC) in the United States, lemurs that roam the outdoor enclosures have been observed eating poison ivy (Taxicodendron radicans), yet have shown no ill effects.[57]
Up to 95% of the greater bamboo lemur's diet consists of bamboo.[52]
Many of the larger lemur species consume leaves (folivory), [85] particularly the indriids.[59] However, some smaller lemurs such as sportive lemurs (genus Lepilemur) and woolly lemurs (genus Avahi) also primarily eat leaves, making them the smallest primates that do so.[61] The smallest of the lemurs generally do not eat much leaf matter.[85] Collectively, lemurs have been documented consuming leaves from at least 82 native plant families and 15 alien plant families. Lemurs tend to be selective in their consumption of the part of the leaf or shoot as well as its age. Often, young leaves are preferred over mature leaves.[85]
Many lemurs that eat leaves tend to do so during times of fruit scarcity, sometimes suffering weight loss as a result.[86] Most lemur species, including most of the smallest lemurs and excluding some of the indriids, predominantly eat fruit (frugivory) when available. Collectively, lemurs have been documented consuming fruit from at least 86 native plant families and 15 alien plant families. As with most tropical fruit eaters, the lemur diet is dominated by fruit from Ficus (fig) species.[85] In many anthropoid primates, fruit is a primary source of vitamin C, but unlike anthropoid primates, lemurs (and all strepsirrhines) can synthesize their own vitamin C.[87] Historically, captive lemur diets high in vitamin C-rich fruits have been thought to cause hemosiderosis, a type of iron overload disorder, since vitamin C increases iron absorption. Although lemurs in captivity have been shown to be prone to hemosiderosis, the frequency of the disease varies across institutions and may depend on the diet, husbandry protocols, and genetic stock. Assumptions about the problem need to be tested separately for each species.[88] The ring-tailed lemur, for instance, seems to be less prone to the disorder than other lemur species.[89]
Only eight species of lemur are known to be seed predators (granivores), but this may be under-reported since most observations only report fruit consumption and do not investigate whether the seeds are consumed as well. These lemurs include some indriids, such as the diademed sifaka (Propithecus diadema), the golden-crowned sifaka (Propithecus tattersalli), the indri, [11][63] and the aye-aye. The aye-aye, which specializes in structurally defended resources, can chew through Canarium seeds, which are harder than the seeds that New World monkeys are known to break open.[45] At least 36 genera from 23 families of plants are targeted by lemur seed predators.[85]
Inflorescences (clusters of flowers) of at least 60 plant families are eaten by lemurs ranging in size from the tiny mouse lemurs to the relatively large ruffed lemurs. If the flowers are not exploited, sometimes the nectar is consumed (nectarivory) along with the pollen (palynivory). At least 24 native species from 17 plant families are targeted for nectar or pollen consumption.[85]
Bark and plant exudates such as tree sap are consumed by a few lemur species. The exploitation of exudates has been reported in 18 plant species and only in the dry regions in the south and west of Madagascar. Only the Masoala fork-marked lemur (Phaner furcifer) and Coquerel's giant mouse lemur regularly consume tree sap. Bark has never been reported as an important food item in lemur diets, but at least four species eat it: the aye-aye, the red-tailed sportive lemur (Lepilemur ruficaudatus), the common brown lemur (Eulemur fulvus), and Verreaux's sifaka (Propithecus verreauxi). Most bark feeding is directly linked to exudate feeding, except for the aye-aye's bark feeding on Afzelia bijuga (genus Afzelia) at Nosy Mangabe in the northeast.[85]
Soil consumption (geophagy) has also been reported and likely helps with digestion, provides minerals and salts, and helps absorb toxins. Sifakas have been observed eating soil from termite mounds, possibly adding beneficial intestinal flora to aid the digestion of cellulose from their folivorous diet.[57]
[edit]Social systems
Lemurs are social and live in groups that usually include less than 15 individuals.[11] Observed social organization patterns include "solitary but social", "fission-fusion", "pair bonds", and "multi-male group".[90] Nocturnal lemurs are mostly solitary but social, foraging alone at night but often nesting in groups during the day. The degree of socialization varies by species, gender, location, and season.[26][35] In many nocturnal species, for instance, the females, along with their young, will share nests with other females and possibly one male, whose larger home range happens to overlap one or more female nesting groups. In sportive lemurs and fork-marked lemurs, one or two females may share a home range, possibly with a male. In addition to sharing nests, they will also interact vocally or physically with their range-mate while they forage at night.[35] Diurnal lemurs exhibit many of the social systems seen in monkeys and apes, [11][35] living in relatively permanent and cohesive social groups. Multi-male groups are the most common, just as they are in most anthropoid primates. True lemurs utilize this social system, often living in groups of ten or less. Ruffed lemurs have been shown to live in fission-fusion societies, [35] and Indri forms pair bonds.[90]
Dwarf lemurs are solitary but social, foraging alone but often sleeping in groups.
Some lemurs exhibit female philopatry, where females stay within their natal range and the males migrate upon reaching maturity, and in other species both sexes will migrate.[11] In some cases, female philopatry may help explain the evolution of female-bonded multi-male groups, such as those of the ring-tailed lemur, Milne-Edwards' sifaka (Propithecus edwardsi), and the Verreaux's sifaka. Their ancestors may have been more solitary, with females that lived in mother-daughter pairs (or dyads). Over time, these dyads may have allied themselves with other neighboring mother-daughter dyads in order to defend more distributed resources in a wide home range. If this is true, then multi-male groups in lemurs may differ fundamentally in their internal structure from those in catarrhine primates (Old World monkeys and apes).[91]
The presence of female social dominance sets lemurs apart from most other primates and mammals;[11][35][38][92] in most primate societies, males are dominant unless females band together to form coalitions that displace them.[93] However, many Eulemur species are exceptions[35][65] and the greater bamboo lemur (Prolemur simus) does not exhibit female dominance.[94] When females are dominant within a group, the way they maintain dominance varies. Ring-tailed lemur males act submissively with or without signs of female aggression. Male crowned lemurs (Eulemur coronatus), on the other hand, will only act submissively when females act aggressively towards them. Female aggression is often associated with, but not limited to, feeding.[95]
There have been many hypotheses that have attempted to explain why lemurs exhibit female social dominance while other primates with similar social structures do not, [11][92] but no consensus has been reached after decades of research. The dominant view in the literature states that female dominance is an advantageous trait given the high costs of reproduction and the scarcity of resources available.[92] Indeed, female dominance has been shown to be linked to increased maternal investment.[93] However, when reproductive costs and extreme seasonality of resources were compared across primates, other primates demonstrated male dominance under conditions that were similar to or more challenging than those faced by lemurs. In 2008, a new hypothesis revised this model using simple game theory. It was argued that when two individuals were equally matched in fighting capacity, the one with the most need would win the conflict since it would have the most to lose. Consequently, the female, with higher resource needs for pregnancy, lactation, and maternal care, was more likely to win in resource conflicts with equally sized males. This, however, assumed monomorphism between sexes.[92] The following year, a new hypothesis was proposed to explain monomorphism, stating that because most female lemurs are only sexually receptive for a day or two each year, males can utilize a more passive form of mate guarding: copulatory plugs, which block the female reproductive tract, preventing other males from successfully mating with her, and thus reducing the need for aggression and the evolutionary drive for sexual dimorphism.[31]
Social grooming serves many functions for social lemurs.
In general, levels of agonism (or aggression) tend to correlate with relative canine height. The ring-tailed lemur has long, sharp upper canine teeth in both sexes, and it also exhibits high levels of agonism. The Indri, on the other hand, has smaller canines and exhibits lower levels of aggression.[29] When neighboring groups of the same species defend their territories, the conflict can take the form of ritualized defense. In sifakas, these ritualized combats involve staring, growling, scent-marking, and leaping to occupy certain sections of the tree. The indri defends its home range with ritualized "singing" battles.[11]
Like other primates, lemurs groom socially (allogroom) to ease tensions and solidify relationships. They groom in greeting, when waking up, when settling in for sleep, between mother and infant, in juvenile relations, and for sexual advances.[96] Unlike anthropoid primates, who part the fur with the hands and pick out particles with the fingers or mouth, lemurs groom with their tongue and scraping with their toothcomb.[11][96] Despite the differences in technique, lemurs groom with the same frequency and for the same reasons as anthropoids.[96]
[edit]Activity patterns
The biological rhythm can vary from nocturnal in smaller lemurs to diurnal in most larger lemurs. Diurnality is not seen in any other prosimian.[26] Cathemerality, where an animal is active sporadically both day and night, occurs among some of the larger lemurs. Few if any other primates exhibit this sort of activity cycle, [97] either regularly or irregularly under changing environmental conditions.[11] The most heavily studied cathemeral lemurs are the true lemurs.[38][98] Although the mongoose lemur (E. mongoz) is the best-documented example, every species in the genus studied has shown some degree of cathemeral behavior, [65] although night activity is often restricted by light availability and moon periodicity.[12] This type of behavior was first documented in the 1960s in true lemur species as well as other Lemuridae species, such as ruffed lemurs and bamboo lemurs. Initially described as "crepuscular" (active at dawn and dusk), anthropologist Ian Tattersall stimulated additional research and coined the new term "cathemeral", [97] although many non-anthropologists prefer the terms "circadian" or "diel".[12]
In order to conserve energy and water in their highly seasonal environment, [82][99] mouse lemurs and dwarf lemurs exhibit seasonal behavioral cycles of dormancy where the metabolic rate and body temperature are lowered. They are the only primates known to do so.[82] They accumulate fat reserves in their hind legs and the base of their tail before the dry winter season, when food and water are scarce, [27][83] and can exhibit daily and prolonged torpor during the dry season. Daily torpor constitutes less than 24 hours of dormancy, whereas prolonged torpor averages two weeks in duration and signals hibernation.[82] Mouse lemurs have been observed experiencing torpor that lasts for several consecutive days, but dwarf lemurs are known to hibernate for six to eight months every year, [26][27][84] particularly on the west coast of Madagascar.[99]
Dwarf lemurs are the only primates known to hibernate for extended periods.[82][100] Unlike other hibernating mammals from temperate regions, which have to awaken regularly for a few days, dwarf lemurs experience five months of continuous deep hibernation (May through September). Before and after this deep hibernation, there are two months (April and October) of transition, where they will forage on a limited basis to reduce demands on their fat reserves.[99] Unlike any other hibernating mammal, the body temperature of hibernating dwarf lemurs will fluctuate with the ambient temperature rather than remaining low and stable.[27][84][99]
Other lemurs that do not exhibit dormancy conserve energy by selecting thermoregulated microhabitats (such as tree holes), sharing nests, and reducing exposed body surfaces, such as by hunched sitting and group huddling. Also, the ring-tailed lemur, ruffed lemurs, and sifakas are commonly seen sunning, thus using solar radiation to warm their bodies instead of metabolic heat.[82]
[edit]Locomotion
Sifakas are specially adapted to vertical clinging and leaping, so they must hop sideways to move on the ground.
Locomotor behavior in lemurs, both living and extinct, is highly varied and its diversity exceeds that of anthropoids.[35] Locomotor postures and behaviors have included vertical clinging and leaping (including saltatory behavior), seen in indriids and bamboo lemurs;[35][59] slow (loris-like) arboreal quadrupedal locomotion, once exhibited by Mesopropithecus;[101] fast arboreal quadrupedal locomotion, seen in true lemurs and ruffed lemurs;[35][102] partially terrestrial quadrupedal locomotion, seen in the ring-tailed lemur; highly terrestrial quadrupedal locomotion, once exhibited by monkey lemurs such as Hadropithecus;[35] and sloth-like suspensory locomotion, once exhibited by many of the sloth lemurs, such as Palaeopropithecus.[11][35] The Lac Alaotra gentle lemur (Hapalemur alaotrensis) has even been reported to be a good swimmer.[11] Sometimes these locomotor types are lumped together into two main groups of lemurs, the vertical clingers and leapers and the arboreal (and occasionally terrestrial) quadrupeds.[57]
The jumping prowess of the indriids have been well documented and are popular among ecotourists visiting Madagascar.[103] Using their long, powerful back legs, they catapult themselves into the air and land in an upright posture on a nearby tree, with both hands and feet tightly gripping the trunk.[13] Indriids can leap up to 10 m (33 ft) rapidly from tree trunk to tree trunk, [13][62] an ability referred to as "ricochetal leaping".[72] Verreaux's sifaka (Propithecus verreauxi) manages to do this in the spiny forests of southern Madagascar. It is unknown how it avoids impaling its palms on the thorn-covered trunks of large plants such as Alluaudia.[13] When distances between trees are too great, sifakas will descend to the ground and cross distances more than 100 m (330 ft) by standing upright and hopping sideways with the arms held to the side and waving up and down from chest to head height, presumably for balance.[13][62] This is sometimes described as a "dance-hop".[13]
[edit]Communication
Lemur communication can be transmitted through sound, sight, and smell (olfaction). The ring-tailed lemur, for instance, uses complex though highly stereotyped behaviors such as scent-marking and vocalizations.[81] Visual signals are probably the least used by lemurs, since they lack many of the muscles used in common primate facial expressions.[79] Given their poor vision, whole-body postures are probably more noticeable. However, the Ring-tailed Lemur has demonstrated distinct facial expressions including a threat stare, pulled back lips for submission, and pulled back ears along with flared nostrils during scent-marking.[81] This species has also been observed using yawns as threats.[104][105] Their ringed tails also communicate distance, warn off neighboring troops, and help locate troop members.[81] Sifakas are known to exhibit an open-mouth play face[106] as well as a submissive teeth-baring grimace used in agonistic interactions.[63]
Lemurs communicate by scent-marking their territory.
Olfaction is particularly important to lemurs, [11] except for the indri, which lacks most common lemur scent glands and has a greatly reduced olfactory region in the brain.[72] Olfaction can communicate information about age, sex, reproductive status, as well as demarcate the boundaries of a territory. It is most useful for communication between animals that rarely encounter each other.[45] Small, nocturnal lemurs mark their territories with urine, while the larger, diurnal species use scent glands located on various parts of their anatomy. The ring-tailed lemur engages in "stink fights" by rubbing its tail across scent glands on its wrists, and then flicking its tail at other male opponents. Some lemurs defecate in specific areas, otherwise known as latrine behavior. Although many animals exhibit this behavior, it is a rare trait among primates. Latrine behavior can represent territorial marking and aid in interspecies signaling.[12]
Compared to other mammals, primates in general are very vocal, and lemurs are no exception.[12] Some lemur species have extensive vocal repertoires, including the Ring-tailed Lemur and ruffed lemurs.[81][107] Some of the most common calls among lemurs are predator alarm calls. Lemurs not only respond to alarm calls of their own species, but also alarm calls of other species and those of non-predatory birds. The Ring-tailed Lemur and a few other species have different calls and reactions to specific types of predators.[35] With mating calls, it has been shown that mouse lemurs that cannot be discerned visually respond more strongly to the calls of their own species, particularly when exposed to the calls of other mouse lemurs that they would encounter normally within their home range.[66] Lemur calls can also be very loud and carry long distances. Ruffed lemurs use several loud calls that can be heard up to 1 km (0.62 mi) away on a clear, calm day.[107] The loudest lemur is the indri, whose calls can be heard up to 2 km (1.2 mi) or more[46][56] and thus communicate more effectively the territorial boundaries over its 34 to 40 hectares (0.13 to 0.15 sq mi) home range.[72] Both ruffed lemurs and the indri exhibit contagious calling, where one individual or group starts a loud call and others within the area join in.[56][107] The song of the indri can last 45 seconds to more than 3 minutes and tends to coordinate to form a stable duet comparable to that of gibbons.[56][61]
Tactile communication (touch) is mostly used by lemurs in the form of grooming, although the ring-tailed lemur also clumps together to sleep (in an order determined by rank), reaches out and touches adjacent members, and cuffs other members. Reaching out and touching another individual in this species has been shown to be a submissive behavior, done by younger or submissive animals towards older and more dominant members of the troop. Allogrooming, however, appears to occur more frequently between higher ranking individuals, a shared trait with other primate species.[108] Unlike anthropoid primates, lemur grooming seems to be more intimate and mutual, often directly reciprocated. Anthropoids, on the other hand, use allogrooming to manage agonistic interactions.[109] The Ring-tailed Lemur is known to be very tactile, spending between 5 and 11% of its time grooming.[108]
Sample lemur vocalizations
Indri duet
The wailing "song" of the Indri
Gray Mouse Lemur alarm call
High-frequency, fast-paced squeaks emitted when startled
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Ring-tailed Lemur cackle
A defensive but confrontational vocalization
Ruffed lemur roar/shriek chorus
An intergroup spacing call
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[edit]Predator avoidance
Lemur alarm calls
Three types of clicks followed by loud yaps
Mammalian predator alert by a ring-tailed lemur
High-amplitude, pulsed squawks
Mammalian predator alert by a ruffed lemur
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All lemurs experience some predation pressure.[110] Common defenses against predation include the use of alarm calls and predator mobbing, [111] mostly among diurnal lemurs.[35] The leaping abilities of lemurs may have evolved for predator avoidance rather than for travel, according to a study in kinematics.[112] Nocturnal lemurs are difficult to see and track at night and decrease their visibility by foraging alone. They also try to avoid predators by using concealing sleeping locations, such as nests, tree holes, or dense vegetation, [35] and alternating between multiple sleeping locations.[27] Even torpor and hibernation states among cheirogaleids may be partly due to high levels of predation.[110] Infants are protected while foraging by either leaving them in the nest or by stashing them in a hidden location, where the infant remains immobile in the absence of the parent.[35]
Diurnal lemurs are visible during the day, so many live in groups, where the increased number of eyes and ears helps aid in predator detection. Diurnal lemurs use and respond to alarm calls, even those of other lemur species and non-predatory birds. The ring-tailed lemur has different calls and reactions to different classes of predators, such as predatory birds, mammals, or snakes.[35] Some lemurs, such as the indri, use crypsis to camouflage themselves. They are often heard but difficult to see in the trees due to the dappled light, earning them the reputation of being "ghosts of the forest".[72]
[edit]Reproduction
Except for the aye-aye and the Lac Alaotra gentle lemur, lemurs are seasonal breeders[11][38] with very short mating and birth seasons influenced by the highly seasonal availability of resources in their environment. Mating seasons usually last less than three weeks each year, [35] with the female vagina opening up only during a few hours or days of her most receptive time of estrus.[77] These narrow windows for reproduction and resource availability appear to relate to their short gestation periods, rapid maturation, and low basal metabolic rates, as well as the high energy costs of reproduction for females. This may also relate to the relatively high mortality rate among adult females and the higher proportion of adult males in some lemur populations—both unusual traits among primates. In both the aye-aye and Lac Alaotra gentle lemur, birth (parturition) occurs over a six-month period.[11]
Lemurs time their mating and birth seasons so that all weaning periods are synchronized to match the time of highest food availability.[77][86] Weaning occurs either before or shortly after the eruption of the first permanent molars in lemurs.[29] Mouse lemurs are able to fit their entire breeding cycle into the wet season, whereas larger lemurs, such as sifakas, must lactate for two months during the dry season.[86] Infant survival in some species, such as Milne-Edwards' Sifaka, has been shown to be directly impacted by both environmental conditions and the rank, age, and health of the mother. The breeding season is also affected by geographical location. For example, mouse lemurs give birth between September and October in their native habitat in the southern hemisphere, but from May through June in the captive settings in the northern hemisphere.[77]
Woolly lemurs are nocturnal and typically give birth to one offspring, which they carry with them while foraging.
Scent factors heavily into lemur reproduction. Scent-marking activity escalates during the mating season. Pheromones may coordinate reproductive timing for females coming into estrus.[77] Mating can be either monogamous or promiscuous for both males and females, and mating can include individuals from outside the group.[11][35] Monogamous lemurs include the red-bellied lemur (Eulemur rubriventer) and the mongoose lemur (Eulemur mongoz), although the Mongoose Lemur has been observed mating outside of its pair bond.[35] Monogamy is most common among nocturnal species, although some exhibit scramble competition, sexual suppression of subordinates, or competitions between males that avoid direct fighting.[29] In mouse lemurs, males utilize sperm plugs, developed enlarged testes during the mating season, and develop size dimorphism (likely due to the enlarged testes). These indicate a mating system known as scramble competition polygyny, where males cannot defend females or the resources that might attract them.[113]
The gestation period varies within lemurs, ranging from 9 weeks in mouse lemurs and 9–10 weeks in dwarf lemurs to 18–24 weeks in other lemurs.[77] The smaller, nocturnal lemurs, such as mouse lemurs, giant mouse lemurs, and dwarf lemurs, usually give birth to more than one infant, whereas the larger, nocturnal lemurs, such as fork-marked lemurs, sportive lemurs, and the aye-aye usually have one offspring.[26] Dwarf and mouse lemurs have up to four offspring, but both average only two. Ruffed lemurs are the only large, diurnal lemurs to consistently give birth to two or three offspring. All other lemurs have single births. Multiple births in lemurs are normally fraternal, and are known to occur in every five to six births in species such as the ring-tailed lemur and some Eulemur.[77]
After the offspring are born, lemurs either carry them around or stash them while foraging. When transported, the infants either cling to the mother's fur or are carried in the mouth by the scruff. In some species, such as bamboo lemurs, infants are carried by mouth until they are able to cling to their mother's fur.[114] Species that park their offspring include nocturnal species (e.g. mouse lemurs, sportive lemurs, and dwarf lemurs), bamboo lemurs, and ruffed lemurs.[26][114] In the case of the ruffed lemurs, the young are altricial and the mothers build nests for them, much like the smaller, nocturnal lemur species.[11] Woolly lemurs are unusual for nocturnal lemurs because they live in cohesive family groups and carry their single offspring with them rather than parking them.[59][60] Alloparenting (multiple or group parenting) has been reported in all lemur families except the sportive lemurs and aye-aye. Allonursing is also known to occur in several lemur gr |
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Cheirogaleidae is the family of strepsirrhine primates that contains the various dwarf and mouse lemurs. Like all other lemurs, cheirogaleids live exclusively on the island of Madagascar.
Contents [hide]
1 Characteristics
2 Classification
3 Footnotes
4 References
[edit]Characteristics
Cheirogaleids are smaller than the other lemurs and, in fact, they are the smallest primates. They have a soft, long fur colored grey-brown to reddish on top with a generally brighter underbelly. Typically they have small ears, large, close set eyes, and long hind legs. Like all strepsirrhines they have fine claws at the second toe of the hind legs. They grow to a size of only 13 to 28 cm, with a tail that is very long, sometimes up to one and a half times as long as the body. They weigh no more than 500 grams, with some species weighing as little as 60 grams.[3]
Dwarf and mouse lemurs are nocturnal and arboreal. They are excellent climbers and can also jump far, using their long tail for balance. When on the ground (a rare occurrence) they move by hopping on their hind legs. They spend the day in tree hollows or leaf nests. Cheirogaleids are typically solitary but sometimes live together in pairs.
Their eyes possess a tapetum lucidum, a light-reflecting layer that improves their night vision. Some species, such as the Lesser Dwarf Lemur, store fat at the hind legs and the base of the tail and hibernate. Unlike lemurids, they have long upper incisors, although they do have the comb-like teeth typical of all strepsirhines. They have the dental formula:
Cheirogaleids are omnivores, eating fruits, flowers and leaves (and sometimes nectar) as well as insects, spiders and small vertebrates.[3]
The females usually have three pairs of nipples. After a meager 60 day gestation, they will bear two to four (usually two or three) young. After five to six weeks these are weaned and become fully mature near the end of their first year or sometime in their second year, depending on the species. In human care, they can live for up to 15 years, although their life expectancy in the wild is probably significantly shorter.
[edit]Classification
The five genera of cheirogaleids contain 32 species.[4][5][6][7]
Infraorder Lemuriformes
Family Cheirogaleidae
Genus Cheirogaleus: dwarf lemurs
C. medius group
Fat-tailed Dwarf Lemur, Cheirogaleus medius
Southern Fat-tailed Dwarf Lemur, Cheirogaleus adipicaudatus
C. major group
Greater Dwarf Lemur, Cheirogaleus major
Furry-eared Dwarf Lemur, Cheirogaleus crossleyi
Lesser Iron-gray Dwarf Lemur, Cheirogaleus minusculus
Greater Iron-gray Dwarf Lemur, Cheirogaleus ravus
Sibree's Dwarf Lemur, Cheirogaleus sibreei
Genus Microcebus: mouse lemurs
Gray Mouse Lemur, Microcebus murinus
Reddish-gray Mouse Lemur, Microcebus griseorufus
Golden-brown Mouse Lemur, Microcebus ravelobensis
Northern Rufous Mouse Lemur, Microcebus tavaratra
Sambirano Mouse Lemur, Microcebus sambiranensis
Simmons' Mouse Lemur, Microcebus simmonsi
Pygmy Mouse Lemur, Microcebus myoxinus
Brown Mouse Lemur, Microcebus rufus
Madame Berthe's Mouse Lemur, Microcebus berthae
Goodman's Mouse Lemur, Microcebus lehilahytsara
Jolly's Mouse Lemur, Microcebus jollyae
MacArthur's Mouse Lemur, Microcebus macarthurii
Mittermeier's Mouse Lemur, Microcebus mittermeieri
Claire's Mouse Lemur, Microcebus mamiratra
Bongolava Mouse Lemur, Microcebus bongolavensis
Danfoss' Mouse Lemur, Microcebus danfossi
Arnhold's Mouse Lemur, Microcebus arnholdi [7]
Margot Marsh's Mouse Lemur, Microcebus margotmarshae [7]
Genus Mirza: giant mouse lemurs
Coquerel's Giant Mouse Lemur or Coquerel's Dwarf Lemur, Mirza coquereli
Northern Giant Mouse Lemur, Mirza zaza
Genus Allocebus
Hairy-eared Dwarf Lemur, Allocebus trichotis
Genus Phaner: fork-crowned lemurs
Masoala Fork-crowned Lemur, Phaner furcifer
Pale Fork-crowned Lemur, Phaner pallescens
Pariente's Fork-crowned Lemur, Phaner parienti
Mt. d’Ambre Fork-crowned Lemur, Phaner electromontis |
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