Tuesday, October 15, 2013

Dwarf lemurs are the only primates known to hibernate

Dwarf lemurs are the only primates known to hibernate for extended periods.[90][108] 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.[107] DELL Latitude 120L Series CPU FAN Unlike any other hibernating mammal, the body temperature of hibernating dwarf lemurs will fluctuate with the ambient temperature rather than remaining low and stable. 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. DELL Latitude 131L Series CPU FAN 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][63] slow (loris-like) arboreal quadrupedal locomotion, once exhibited by Mesopropithecus;[109] fast arboreal quadrupedal locomotion, seen in true lemurs and ruffed lemurs;[ DELL Latitude C500 CPU FAN 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] DELL Latitude C540 CPU FAN 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.[61] The jumping prowess of the indriids have been well documented and are popular among ecotourists visiting Madagascar.[111] 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.[13DELL Latitude C600 CPU FAN ] Indriids can leap up to 10 m (33 ft) rapidly from tree trunk to tree trunk,[13][66] an ability referred to as "ricochetal leaping".[76] 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 asAlluaudia.[13] When distances between trees are too great, DELL Latitude C610 CPU FAN 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][66] This is sometimes described as a "dance-hop". Lemur communication can be transmitted through sound, sight, and smell (olfaction). DELL Latitude C640 CPU FAN The ring-tailed lemur, for instance, uses complex though highly stereotyped behaviors such as scent-marking and vocalizations.[87] Visual signals are probably the least used by lemurs, since they lack many of the muscles used in common primate facial expressions.[85] 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.[87] DELL Latitude C800 Series CPU FAN This species has also been observed using yawns as threats.[112][113] Their ringed tails also communicate distance, warn off neighboring troops, and help locate troop members.[87] Sifakas are known to exhibit an open-mouth play face[114] as well as a submissive teeth-baring grimace used in agonistic interactions. 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.[76] DELL Latitude C810 Series CPU FAN 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.[49] 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. DELL Latitude C840 Series CPU FAN 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.[87][115] DELL Latitude D400 Series CPU FAN 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] DELL Latitude D410 Series CPU FAN 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.[70] 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.[115] DELL Latitude D420 CPU FAN The loudest lemur is the indri, whose calls can be heard up to 2 km (1.2 mi) or more[50][60] and thus communicate more effectively the territorial boundaries over its 34 to 40 hectares (0.13 to 0.15 sq mi) home range.[76] 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.[60][115] 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.[60][65] DELL Latitude D430 CPU FAN 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. DELL Latitude D500 Series CPU FAN Allogrooming, however, appears to occur more frequently between higher ranking individuals, a shared trait with other primate species.[116] 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.[117] The ring-tailed lemur is known to be very tactile, spending between 5 and 11% of its time grooming. DELL Latitude D505 Series CPU FAN All lemurs experience some predation pressure.[118] Common defenses against predation include the use of alarm calls and predator mobbing,[119] 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.[120] Nocturnal lemurs are difficult to see and track at night and decrease their visibility by foraging alone. DELL Latitude D510 Series CPU FAN They also try to avoid predators by using concealing sleeping locations, such as nests, tree holes, or dense vegetation,[35] Some may also avoid areas frequented by predators by detecting the smell of their feces.[121] and alternating between multiple sleeping locations.[27] Even torpor and hibernation states among cheirogaleids may be partly due to high levels of predation.[118] DELL Latitude D531 CPU FAN 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. DELL Latitude D600 Series CPU FAN 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". Except for the aye-aye and the Lac Alaotra gentle lemur, lemurs are seasonal breeders with very short mating and birth seasons influenced by the highly seasonal availability of resources in their environment. DELL Latitude D610 Series CPU FAN 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.[83] 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. DELL Latitude D620 CPU FAN 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.[ DELL Latitude D630 CPU FAN 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.[94] 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. DELL Latitude D800 Series CPU FAN 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. Scent factors heavily into lemur reproduction. Scent-marking activity escalates during the mating season. Pheromones may coordinate reproductive timing for females coming into estrus.[83] DELL Latitude D810 Series CPU FAN 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 (E. mongoz), although the mongoose lemur has been observed mating outside of its pair bond.[35]Monogamy is most common among nocturnal species, DELL Latitude D820 CPU FAN 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 testesduring the mating season, and develop size dimorphism (likely due to the enlarged testes). These indicate a mating system known asscramble competition polygyny, where males cannot defend females or the resources that might attract them.[122] DELL Latitude D830 CPU FAN 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.[83] 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] DELL Latitude E4200 Series CPU FAN 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 someEulemur.[83] After the offspring are born, lemurs either carry them around or stash them while foraging. DELL Latitude E4300 Series CPU FAN 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.[123] Species that park their offspring include nocturnal species (e.g. mouse lemurs, sportive lemurs, and dwarf lemurs), bamboo lemurs, and ruffed lemurs.[26][123] In the case of the ruffed lemurs, the young are altricial and the mothers build nests for them, much like the smaller, DELL LATITUDE E4310 Series CPU FAN 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.[63][64] 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 groups.[124] Even males have been observed caring for infants in species such as the red-bellied lemur, mongoose lemur,[69DELL Latitude E5400 CPU FAN] eastern lesser bamboo lemur, silky sifaka,[124] fat-tailed dwarf lemur,[125] and ruffed lemurs.[126] Yet another trait that sets most lemurs apart from anthropoid primates is their long lifespan together with their high infant mortality.[94] Many lemurs, including the ring-tailed lemur, have adapted to a highly seasonal environment, which has affected their birthrate, maturation, and twinning rate (r-selection). DELL Latitude E5500 CPU FAN This helps them to recover rapidly from a population crash.[87] In captivity, lemurs can live twice as long as they do in the wild, benefiting from consistent nutrition that meets their dietary requirements, medical advancements, and improved understanding of their housing requirements. In 1960, it was thought that lemurs could live between 23 and 25 years. We now know that the larger species can live for more than 30 years without showing signs of aging (senescence) and still be capable of reproduction. Lemurs have traditionally been regarded as being less intelligent than anthropoid primates,[127] DELL Latitude E6400 Series CPU FAN with monkeys and apes often described as having more cunning, guile, and deceptiveness.[13] Many lemur species, such as sifakas and the ring-tailed lemur, have scored lower on tests designed for monkeys while performing as well as monkeys on other tests.[13][104] These comparisons may not be fair since lemurs prefer to manipulate objects with their mouths (rather than their hands) and only take interest in objects when in captivity.[104] DELL Latitude E6410 CPU FAN Recent studies have shown that lemurs exhibit levels of technical intelligence on par with many other primates, although they manipulate objects less often.[128] Tool use has not been witnessed by lemurs in the wild, although in captivity the common brown lemur and the ring-tailed lemur have been demonstrated to be able to understand and use tools.[12] A few lemurs have been noted to have relatively large brains. DELL Latitude E6410 Series CPU FAN The extinct Hadropithecus was as large as a large male baboon and had a comparably sized brain, giving it the largest brain size relative to body size among all prosimians.[129] The aye-aye also has a large brain-to-body ratio, which may indicate a higher level of intelligence.[39] However, despite having a built-in tool in the form of its thin, elongated middle finger, which it uses to fish for insect grubs, the aye-aye has tested poorly in the use of extraneous tools. DELL Latitude E6420 CPU FAN Madagascar not only contains two radically different climatic zones, the rainforests of the east and the dry regions of the west,[11] but also swings from extended drought to cyclone-generated floods.[130] These climatic and geographical challenges, along with poor soils, low plant productivity, wide ranges ofecosystem complexity, and a lack of regularly fruiting trees (such as fig trees) have driven the evolution of lemurs' immense morphological and behavioral diversity .DELL Latitude E6500 CPU FAN Their survival has required the ability to endure the persistent extremes, not yearly averages. Lemurs have either presently or formerly filled the ecological niches normally occupied by monkeys, squirrels, woodpeckers, and grazing ungulates.[13] With the diversity of adaptations for specific ecological niches, habitat selections among lemur families and some genera are often very distinct, thus minimizing competition.[11] DELL Latitude E6500 Series CPU FAN In nocturnal lemurs from the more seasonal forests in the west, up to five species can coexist during the wet season due to high food abundance. However, to endure the extreme dry season, three of the five species utilize different dietary patterns and their underlying physiological traits to allow them to coexist: fork-marked lemurs feed on tree gum, sportive lemurs feed on leaves, and giant mouse lemurs sometimes feed on insect secretions. DELL Latitude E6510 CPU FAN The other two species, the gray mouse lemur and the fat-tailed dwarf lemur (Cheirogaleus medius), avoid competition through reduced activity. The gray mouse lemur uses bouts of torpor, while the fat-tailed dwarf lemur hibernates completely.[26]Similarly, on the east coast entire genera focus on specific food to avoid too much niche overlap. True lemurs and ruffed lemurs are frugivorous, indriids are folivorous, and bamboo lemurs specialize in bamboo and other grasses. DELL Latitude E6510 Series CPU FAN Once again, seasonal dietary differences as well as subtle differences in substrate preferences, forest strata used, activity cycle, and social organization enable lemur species to coexist, although this time the species are more closely related and have similar niches.[11] A classic example involves resource partitioning between three species of bamboo lemur that live in close proximity in small forested areas: the golden bamboo lemur, the greater bamboo lemur, and the eastern lesser bamboo lemur (Hapalemur griseus). DELL Precision M4400 Series CPU FAN

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