Gray Mouse Lemur
Encyclopedia
The gray mouse lemur or lesser mouse lemur, is a small lemur
, a type of strepsirrhine
primate
, found only on the island of Madagascar
. Weighing 58 to 67 g (2 to 2.4 oz), it is the largest of the mouse lemur
s (genus
Microcebus), a group which include the smallest primates in the world. The species is named for its mouse
-like size and coloration and is known locally (in Malagasy
) as tsidy, koitsiky, titilivaha, pondiky, and vakiandry. Nearly indistinguishable from each other by appearance, the gray mouse lemur and all other mouse lemurs are considered cryptic species
. For this reason, the gray mouse lemur was considered the only mouse lemur species for decades until more recent studies began to distinguish between the species.
Like all mouse lemurs, this species is nocturnal and arboreal. It is very active, and although it forages alone, groups of males and females will form sleeping groups and share tree holes during the day. It exhibits a form of dormancy
called torpor
during the cool, dry winter months, and in some cases undergoes seasonal torpor (or hibernation
), which is unusual for primates. The gray mouse lemur can be found in several types of forest throughout western and southern Madagascar. Its diet consists primarily of fruit, insects, flowers, and nectar. In the wild, its natural predators include owls, snakes, and endemic mammalian predators. Predation pressure is higher for this species than among any other primate species, with one out of four individuals taken by a predator each year. This is counterbalanced by its high reproductive rate. Breeding is seasonal, and distinct vocalizations are used to prevent hybridization with species that overlap its range. Gestation
lasts approximately 60 days, and typically two young are born. The offspring are usually independent in two months, and can reproduce after one year. The gray mouse lemur has a reproductive lifespan of five years, although captive individuals have been reported to live up to 15 years.
Although threatened by deforestation
, habitat degradation
, and live capture for the pet trade
, it is considered one of Madagascar's most abundant small native mammals. Although it can tolerate moderate food shortages by experiencing daily torpor to conserve energy, extended food shortages due to climate change
would pose a significant risk to the species.
words mikros, meaning "small", and kebos, meaning "monkey". The Latin
version of kebos, cebus, is a common suffix used for primate names, despite the fact that the gray mouse lemur is a lemur, and not a monkey
. The species name, murinus, means "mouse-like" and derives from the Latin word mus, or "mouse", and the Latin suffix -inus, which means "like".
The lemur is known locally by several names in Malagasy, depending upon the region. Around Tôlanaro
(Fort Dauphin), it is called pondiky punˈdikʲ. In the northern end of its range, it is known as tsidy ˈtʃidʲ. Around Morondava
, it is referred to as koitsiky kuiˈtʃikʲ, titilivaha ti̥tiliˈva, and vakiandry vakiˈaɳɖʐʲ. In many cases, these Malagasy names are also used for other visually indistinguishable mouse lemur species that live within its range.
and infraorder
Lemuriformes. Within Lemuriformes, it belongs to the family Cheirogaleidae
, which contains the mouse lemurs, dwarf lemur
s, giant mouse lemur
s, fork-marked lemurs, and hairy-eared dwarf lemur
. The mouse lemur genus Microcebus includes the smallest primates in the world. Phylogenetic analyses of D-loop
DNA sequence
s of various lemur species suggests that the gray mouse lemur may be most closely related to the reddish-gray mouse lemur
(M. griseorufus).
First described in 1777 by English illustrator John Frederick Miller
, M. murinus remained the only species of its genus, as well as the name used for all mouse lemurs on Madagascar, between the first major taxonomic revision in 1931 and an extensive field study conducted in 1972. The field study distinguished the brown mouse lemur, M. rufus—then considered a subspecies—as a distinct, sympatric species in the southeastern part of the island. Upon this revision, the gray mouse lemur was thought to account for all mouse lemurs that lived in the drier parts of the north, west, and south, while the brown mouse lemur represented the eastern rainforest mouse lemurs. More recently, scientific understanding of the distribution and diversity of the mouse lemurs has become much more complex. Additional field studies, genetic testing, and resulting taxonomic revisions throughout the 1990s and 2000s identified numerous new mouse lemur species, demonstrating that the genus includes at least 17 cryptic species
.
to enhance its vision at night. The dorsal coat is brownish-gray with various reddish tones, the flanks are light gray to beige, and the ventral fur has discrete dull beige or whitish-beige patches along portions of the belly. On the rounded face, there is a pale white patch above the nose and between the eyes; some individuals have dark orbital markings. The furred portions of the hands and feet are off-white.
The gray mouse lemur is one of the smallest primates in the world, yet it is also the largest mouse lemur. Its total length is 25 to 28 cm (9.8 to 11 in), with a head-body length of 12 to 14 cm (4.7 to 5.5 in) and a tail
length of 13 to 14.5 cm (5.1 to 5.7 in). The average weight for this species is 60 g (2.1 oz), with ranges of 58 and 67 g (2 and 2.4 oz) and 40 and 70 g (1.4 and 2.5 oz) reported. This is smaller than the world's smallest monkey, the Pygmy Marmoset
, which ranges between 85 and 140 g (3 and 4.9 oz). Weight varies by season, with both sexes building fat reserves, up to 35% of their body weight, in the tail and hind legs prior to the dry season and periods of dormancy.
Researchers have identified differences in the tooth morphology of the first and second molar
s between the gray mouse lemur and the reddish-gray mouse lemur. In the reddish-gray mouse lemur, the first lower molar (m1) is squared and both the first and second upper molars (M1 and M2) have slight indentations around the middle of the posterior margin. The gray mouse lemur has a more elongated m1 and lacks the aforementioned indentation on M1 and M2. In terms of its general dentition
, the gray mouse lemur shares the same dental formula as all other members of its family, Cheirogaleidae:
This species has 66 chromosome
s, closely resembling the karyotype
of the dwarf lemurs (genus Cheirogaleus). Except for the X chromosome
, all chromosomes are acrocentric (with the short arm absent or virtually absent). Its genome size
is 3.12 picograms (pg).
, Cheirogaleidae
, the gray mouse lemur is nocturnal and arboreal. It inhabits lowland tropical dry forest, sub-arid thorn scrub, gallery forest
, spiny forest
, eastern littoral forest, dry deciduous forest
s, semi-humid deciduous, moist lowland forest
, transitional forest, and secondary forest
s or degraded forests (including plantations) all ranging up to 800 m (2,624.7 ft) above sea level. The species is more common in secondary forest than in primary forest, particularly bush and scrub habitat, where it occupies a "fine branch" niche
, restricting the vertical range to fine branches, fine terminal supports, lianes
and dense foliage. These lemurs are usually seen on branches less than 5 cm (2 in) in diameter. The gray mouse lemur tends to prefer lower levels of the forest and the understory
, where branches and vegetation are dense.
In secondary forest, it is generally observed from ground level up to 10 m (32.8 ft) above ground, yet 15 to 30 m (49.2 to 98.4 ft) in the canopy of primary forest. Studies have found that the species can spend as much as 40% of its time below 3 m (9.8 ft), with 70% of its time spent at this level during the end of the dry season, when plant food is limited and insects compose a larger percentage of the diet. The species is more numerous in spiny forest, such as the Andohahela Special Reserve
, than in the gallery forest, preferring drier, littoral forest, whereas the brown mouse lemur prefers inland rain forest.
The limits of the distribution are poorly understood. It is believed to range from the Onilahy River
or Lake Tsimanampetsotsa
in the south to Ankarafantsika National Park
in the north. There is also an isolated and disjointed population in the southeastern part of the island, near Tôlanaro and the Andohahela National Park, up to the Mandena Conservation Zone. Individuals tend to occupy small home ranges of 1 to 2 ha (2.5 to 4.9 acre). The gray mouse lemur is also sympatric
with the reddish-gray mouse lemur, golden-brown mouse lemur, Madame Berthe's mouse lemur
, and several other cheirogaleid
lemurs. In Ankarafantsika National Park
, where it coexists with the golden-brown mouse lemur, the gray mouse lemur's relative population density
was highest at higher altitudes and in drier habitat, while the golden-brown mouse lemur preferred the opposite. Another study has looked at the coexistence of the gray mouse lemur and Madame Berthe's mouse lemur and found small, exclusive clusters of each species and a high degree of feeding niche overlap
.
The gray mouse lemur can reach high population densities up to several hundred individuals per square kilometer (up to 167 individuals/km2 at Ankarafantsika National Park to 712 individuals/km2 at Kirindy Mitea National Park
). This abundance is not uniform and tends to concentrate in "population nuclei", suggesting that it is difficult to accurately estimate population densities when extrapolating from a small area (from various studies) to a large area. The difficulty in finding individuals during some times of the year, particularly during the dry periods, can further complicate the problem of estimating population densities.
Mouse lemurs are omnivorous
, favoring fruit and insects for the bulk of their diet. The gray mouse lemur may even come down to the ground to catch insect prey, although it will quickly return to the protective cover of the understory to consume its catch. Nectar is also a part of the gray mouse lemur's diet, making it a potential pollinator
for local plant species.
s of the gray mouse lemur are the Madagascar long-eared owl
and barn owl
. Studies conducted in Beza Mahafaly Reserve
and Kirindy Mitea National Park indicate a predation rate of around 25% (percent population taken by predator per year), the highest known for any primate species. However, given its high reproductive potential, predation does not appear to drastically impact its populations. Other raptors, such as the Henst's Goshawk
, and owls prey upon this species. Snake
s, such as Ichythcyphys miniatus (a native colubrid
snake), Madagascar Tree Boa, as well as mammalian predators, such as the Ring-tailed Mongoose
, Narrow-striped Mongoose
, Fossa
, and Domestic Dog
s are also known to prey upon the gray mouse lemur. Mammalian predators often discover tree holes serving as nests and then enlarge the opening in order to obtain and eat the occupant, resulting in strong selective pressure
affecting the choice of nest hole opening diameter and deepness.
Due to its non-gregarious nature, the gray mouse lemur, like other nocturnal lemurs, primarily defends itself from predators using avoidance strategies, although group defense through the use of alarm calls and predator mobbing
has been observed in this species. Studies involving the placement of predator and non-predator fecal
odor with captive populations have demonstrated a genetic predisposition for predator recognition through the detection of metabolite
s from meat digestion. The mouse lemurs were shown to avoid locations where they typically received rewards, as well as exhibit increased activity and anti-predator behavior, when the odor of predator feces were present in that vicinity, but not when the fecal odor of Malagasy non-predators was present.
During the day, when they are most vulnerable, individuals will take shelter inside tree holes, sometimes forming nests. Between three and nine different tree holes may be used within their home range, yet individuals will utilize one particular hole for up to five consecutive days. Tree hollows tend to be preferred, but spherical constructions made of leaves are also common. Nests are usually found in tree holes with a minimum diameter of 5 cm (2 in), with a median
of 13 cm (5.1 in), suggesting that this range in diameter of tree holes may be crucial for maintaining a healthy habitat. The gray mouse lemur also spends most of its time in dense vegetation, limiting its visibility and accessibility to predators. Furthermore, it has a high reproductive rate to counter losses to predation.
All mouse lemurs are highly active at night, often scurrying like mice and leaping over 3 m (9.8 ft), using the tail as a balancing organ. When moving among the terminal branches of bushes and trees, they grip using all four feet and move with four legs. When on the ground, either to catch insects or cross short open areas, mouse lemurs hop like a frog.
Foraging behavior is often slow, with height and direction changing continuously. Predation of insects occurs primarily on the ground. Before descending, the ear pinnae move alternately to help pinpoint the precise location of their prey. Insects are captured during a rapid dash across the leaf litter and are transported by mouth up into the relative safety of the branches. Studies with captive gray mouse lemurs have shown that vision is primarily used for prey detection, although the other senses certainly play a role in foraging.
The gray mouse lemur is omnivorous, feeding primarily on fruit and invertebrate
s. Local populations appear to specialize on locally available fruit. At both Marosalaza and Mandena, beetle
s are the primary insect prey, although moths, praying mantid
s, fulgorid bugs, crickets, cockroaches, and spiders are also eaten. Less than half the diet consists of insects, with fruit making up a slightly larger fraction. This lemur also consumes flowers, gums and nectar from Euphorbia and Terminalia
trees, leaves (Uapaca
sp.), exudate
s (Homopteran
larvae secretions), and small vertebrate
s such as tree frog
s, gecko
s, and chameleon
s. Its diet is seasonally varied and diverse in content, giving it a very broad feeding niche, compared to other species such as the Madame Berthe's mouse lemur. Therefore it is affected more by food availability than by niche partitioning where sympatry occurs.
winter. This rare trait in primates, coupled with the ease of observing the species within its wide geographic distribution and its good representation in captivity, makes it a popular subject for research as a model organism
.
The gray mouse lemur is unique among the mouse lemurs studied so far because it is the only species to exhibit prolonged seasonal torpor, but this behavior has only been observed to occur in one locality. Activity patterns can differ noticeably between sexes as well as populations. At the Ampijoroa Forestry Station in Ankarafantsika National Park, males and females exhibit daily, rather than seasonal torpor. At Kirindy Forest, both sexes share the same daily torpor, yet during the dry season (April/May through September/October), females become completely inactive for several weeks or up to five months to conserve energy and reduce predation. However, males rarely remain inactive for more than a few days and become extremely active before the females revive from torpor, allowing them to establish hierarchies and territories for the breeding season
. The use of alternative energy-saving strategies under the same environmental conditions was observed directly in 2008, providing the first physiological confirmation from the field. This pattern of seasonal versus daily torpor may relate to the seasonality of the region, since Kirindy is the only location west of the eastern mountain rainforests that experiences very low temperatures at night during the winter months. By entering extended torpor, sometimes referred to as hibernation, this would reduce the thermoregulatory stress in females, whereas males remain more active in preparation for the upcoming mating season. No difference in mortality has been shown between hibernating females and active males.
During torpor, the gray mouse lemur's metabolic rate slows and its body temperature drops to the ambient temperature, as low as 7 °C (44.6 °F). During the cooler months of May though August, the species selects tree holes closer to ground level, where ambient temperatures remain more stable. This allows them to remain in torpor longer, and to conserve metabolic resources.
This unusual ability for a primate to exhibit dormancy, in addition to the diminutive size, has led researchers to speculate that ancestral lemurs, and possibly ancestral primates, may have shared some traits with mouse lemurs. Consequently, the gray mouse lemur has once again been used as a model organism for studying lemur and primate evolution. For example, lemurs are thought to have colonized Madagascar by rafting
to the island around 60 million years ago according to molecular phylogenetic studies. Before the discovery that ocean currents were the opposite of what they are today, thus favoring such an event, it was thought that it would have taken too long for any animal not capable of entering a state of dormancy to survive the trip. Therefore the mouse lemurs, such as the gray mouse lemur, were thought to have shared this plesiomorphic (ancestral) trait with the ancestral lemurs.
, foraging alone at night, but frequently sleeping in groups during the day. This social pattern varies by gender, season, and location. Females tend to share nests with other females and their offspring, whereas males tend to sleep alone or in pairs outside of the breeding season. Groups of females sharing a nest can be relatively stable, consisting of two to nine individuals, although a male may be found with a group of females outside the breeding season. During the breeding season (September through October), males and females may sleep in the same tree hole. Mixed sex groups can be common at this time, with single males sharing nest sites with three to seven females or single females sharing nest sites with one to three males.
Research has shown that home ranges for the gray mouse lemur are likely to be small, possibly less than 50 m (164 ft). Males typically travel further at night and have home ranges that are twice as large as those of females, often overlapping with one another, and always overlapping with at least one female's home range. Male home ranges increase threefold during the breeding season.
Female home ranges overlap less than those of males, although localized concentrations, or "population nuclei", tend to form in some areas, where the sex ratio favors females to males by three or four to one at the nucleus core. Genetic studies indicate that females arrange themselves spatially in clusters ("population nuclei") of related individuals, while males tend to emigrate from their natal group. Research has shown that females in this species may maintain smaller ranges and associate more closely with other females than in some other mouse lemur species due to a more opportunistic feeding niche and, in the case of populations at Kirindy, the use of extended, seasonal torpor.
are the primarily modes of communication within this species. Home ranges are scent marked with urine and feces. Vocalizations are complex and very high-pitched (ranging from 10 to 36 kHz
), sometimes beyond the range of human hearing (0.02 to 20 kHz). These include calls for seeking contact, mating, distant communication, alarm, and distress.
As with other social mammals, the calls reveal the sex and identity of the individual. Dialects have also been detected between communities. The male trill call, part of the male mating display, is much like a bird song in terms of its ordered sequence of broadband frequency modulated syllables, ranging between 13 to 35 kHz in pitch
and lasting 0.3 to 0.9 seconds, repeating up to 1.5 times per minute. Each locality has its own theme of trill calls that is distinct from those of neighboring communities, and resident males produce individually distinct trill calls within that theme. These calls are not genetically programmed
. During play, young males produce early attempts at the trill call which show high degrees of variability. Research has shown that the male mouse lemurs consciously manipulate the dialect to resemble those of their neighbors, when transferred from their home to a new neighborhood. This may reduce aggression and foster social acceptance for emigrant males as they transfer from their natal group upon maturity.
Because mouse lemurs are cryptic species, and therefore visually indistinguishable, their social calls help individuals select mates of their own species. This differentiated signaling and recognition system has promoted species cohesiveness through premating isolation, and helped researchers distinguish and identify species.
is described as multi-male and multi-female. Males establish dominance hierarchies
prior to the mating season, however, some studies in the wild have shown no male aggression or visible competition for receptive females. Males in captivity become highly aggressive and form strict dominance hierarchies. These captive males may show the highest plasma
testosterone
levels found in mammals, and even the odor of a dominant male can lower the testosterone levels and sexually inhibit a subordinate male. During the breeding season, male testes
increase significantly in size, facilitating sperm competition
due to female promiscuity. Studies with the gray mouse lemur have shown that the optimal insemination period, during which a male is most likely to sire offspring, occurs early during a female's receptivity. Only during the mating season does male mortality rise above that of female mortality.
The females are receptive for 45 to 55 days between September and October, with estrus
lasting 1 to 5 days. Females advertise estrus by distinctive high-frequency calls and scent-marking. Gestation lasts 54 to 68 days, averaging 60 days, typically resulting in 2 or 3 offspring weighing 5 g (0.17636981052556 oz) each. Infants are born in a leaf nest or tree hole in November prior to the onset of the rainy season. Weaning
occurs after 25 days, and the infants are either left in the nest or carried in the mother's mouth and deposited on a branch while she forages. Infant mouse lemurs do not cling to the mother's fur. Independence is attained in 2 months, while sexual maturity is reached at 10 to 29 months in females and 7 to 19 months in males. Closely related females remain loosely associated after maturation (female philopatry
), whereas males disperse from their natal area. In the wild, the gray mouse lemur's reproductive lifespan is no more than 5 years, although captive specimens have reportedly lived as long as 15 years and 5 months.
(LC) with a decreasing population trend. Its greatest threats are habitat loss from slash-and-burn agriculture
and cattle-grazing
, as well as live capture for the local pet trade in the northern and southern parts of its range. Although this species inhabits secondary forests, studies have shown that decreased habitat quality adversely affects its populations since fewer tree holes offer fewer opportunities to conserve energy, increasing stress and mortality. Studies in the late 1960s and 1970s showed that heavy logging between 1968 and 1970 seemed to result in decreased body weight, the use of smaller trees for nesting sites, and a smaller maximum female nesting group size (down to 7 from 15). There is also a concern that although daily torpor can help conserve energy and resources during moderate food shortages, extended food shortages brought about by climate change
could create too much stress and severely impact the survivability of the species.
The gray mouse lemur is considered to be one of Madagascar's most abundant small native mammals, found in seven national parks, five special reserves, the Berenty Private Reserve
, and other privately protected forests within the Mandena Conservation Zone.
This species of mouse lemur breeds very well in captivity, although it is not commonly displayed in zoos like some larger, diurnal lemurs. In 1989, more than 370 individuals were housed by 14 International Species Information System
(ISIS) and non-ISIS institutions across the United States and Europe, 97% of which were captive born. In March 2009, 167 were registered at 29 ISIS institutions, including the Duke Lemur Center
.
Lemur
Lemurs are a clade of strepsirrhine primates endemic to the island of Madagascar. They are named after the lemures of Roman mythology due to the ghostly vocalizations, reflective eyes, and the nocturnal habits of some species...
, a type of strepsirrhine
Strepsirrhini
The clade Strepsirrhini is one of the two suborders of primates. Madagascar's only non-human primates are strepsirrhines, and others can be found in southeast Asia and Africa...
primate
Primate
A primate is a mammal of the order Primates , which contains prosimians and simians. 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...
, found only on the island of Madagascar
Madagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...
. Weighing 58 to 67 g (2 to 2.4 oz), it is the largest of the mouse lemur
Mouse lemur
The mouse lemurs are nocturnal lemurs of the genus Microcebus. Like all lemurs, mouse lemurs are native to Madagascar.Mouse lemurs have a combined head, body and tail length of less than , making them the smallest primates ; however, their weight fluctuates in response to daylight duration.Mouse...
s (genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Microcebus), a group which include the smallest primates in the world. The species is named for its mouse
Mouse
A mouse is a small mammal belonging to the order of rodents. The best known mouse species is the common house mouse . It is also a popular pet. In some places, certain kinds of field mice are also common. This rodent is eaten by large birds such as hawks and eagles...
-like size and coloration and is known locally (in Malagasy
Malagasy language
Malagasy is the national language of Madagascar, a member of the Austronesian family of languages. Most people in Madagascar speak it as a first language as do some people of Malagasy descent elsewhere.-History:...
) as tsidy, koitsiky, titilivaha, pondiky, and vakiandry. Nearly indistinguishable from each other by appearance, the gray mouse lemur and all other mouse lemurs are considered cryptic species
Cryptic species complex
In biology, a cryptic species complex is a group of species which satisfy the biological definition of species—that is, they are reproductively isolated from each other—but whose morphology is very similar ....
. For this reason, the gray mouse lemur was considered the only mouse lemur species for decades until more recent studies began to distinguish between the species.
Like all mouse lemurs, this species is nocturnal and arboreal. It is very active, and although it forages alone, groups of males and females will form sleeping groups and share tree holes during the day. It exhibits a form of dormancy
Dormancy
Dormancy is a period in an organism's life cycle when growth, development, and physical activity are temporarily stopped. This minimizes metabolic activity and therefore helps an organism to conserve energy. Dormancy tends to be closely associated with environmental conditions...
called torpor
Torpor
Torpor, sometimes called temporary hibernation is a state of decreased physiological activity in an animal, usually characterized by a reduced body temperature and rate of metabolism. Animals that go through torpor include birds and some mammals such as mice and bats...
during the cool, dry winter months, and in some cases undergoes seasonal torpor (or hibernation
Hibernation
Hibernation is a state of inactivity and metabolic depression in animals, characterized by lower body temperature, slower breathing, and lower metabolic rate. Hibernating animals conserve food, especially during winter when food supplies are limited, tapping energy reserves, body fat, at a slow rate...
), which is unusual for primates. The gray mouse lemur can be found in several types of forest throughout western and southern Madagascar. Its diet consists primarily of fruit, insects, flowers, and nectar. In the wild, its natural predators include owls, snakes, and endemic mammalian predators. Predation pressure is higher for this species than among any other primate species, with one out of four individuals taken by a predator each year. This is counterbalanced by its high reproductive rate. Breeding is seasonal, and distinct vocalizations are used to prevent hybridization with species that overlap its range. Gestation
Gestation
Gestation is the carrying of an embryo or fetus inside a female viviparous animal. Mammals during pregnancy can have one or more gestations at the same time ....
lasts approximately 60 days, and typically two young are born. The offspring are usually independent in two months, and can reproduce after one year. The gray mouse lemur has a reproductive lifespan of five years, although captive individuals have been reported to live up to 15 years.
Although threatened by deforestation
Deforestation
Deforestation is the removal of a forest or stand of trees where the land is thereafter converted to a nonforest use. Examples of deforestation include conversion of forestland to farms, ranches, or urban use....
, habitat degradation
Habitat destruction
Habitat destruction is the process in which natural habitat is rendered functionally unable to support the species present. In this process, the organisms that previously used the site are displaced or destroyed, reducing biodiversity. Habitat destruction by human activity mainly for the purpose of...
, and live capture for the pet trade
Exotic pet
An exotic pet is a rare or unusual animal pet, or an animal kept as a pet which is not commonly thought of as a pet.The definition is an evolving one; some rodents, reptiles, and amphibians have become firmly enough established in the world of animal fancy to no longer be considered exotic...
, it is considered one of Madagascar's most abundant small native mammals. Although it can tolerate moderate food shortages by experiencing daily torpor to conserve energy, extended food shortages due to climate change
Climate change
Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions or the distribution of events around that average...
would pose a significant risk to the species.
Etymology
The gray or lesser mouse lemur is named for its brownish-gray fur and mouse-like size and appearance. The genus name, Microcebus, derives from the GreekGreek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
words mikros, meaning "small", and kebos, meaning "monkey". The Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
version of kebos, cebus, is a common suffix used for primate names, despite the fact that the gray mouse lemur is a lemur, and not a monkey
Monkey
A monkey is a primate, either an Old World monkey or a New World monkey. There are about 260 known living species of monkey. Many are arboreal, although there are species that live primarily on the ground, such as baboons. Monkeys are generally considered to be intelligent. Unlike apes, monkeys...
. The species name, murinus, means "mouse-like" and derives from the Latin word mus, or "mouse", and the Latin suffix -inus, which means "like".
The lemur is known locally by several names in Malagasy, depending upon the region. Around Tôlanaro
Tôlanaro
Tôlanaro or Tolagnaro is a city in Madagascar. It is the capital of Anosy Region and of Tôlanaro District. It has a port of local importance, and a new port has been built at Ehoala...
(Fort Dauphin), it is called pondiky punˈdikʲ. In the northern end of its range, it is known as tsidy ˈtʃidʲ. Around Morondava
Morondava
Morondava is a city located in Menabe Region, of which it is the capital, in Madagascar. It is located in the delta of the Morandava River at .-Communication:...
, it is referred to as koitsiky kuiˈtʃikʲ, titilivaha ti̥tiliˈva, and vakiandry vakiˈaɳɖʐʲ. In many cases, these Malagasy names are also used for other visually indistinguishable mouse lemur species that live within its range.
Taxonomy
As its name implies, the gray mouse lemur is a lemur, a type of primate, and belongs to the suborder StrepsirrhiniStrepsirrhini
The clade Strepsirrhini is one of the two suborders of primates. Madagascar's only non-human primates are strepsirrhines, and others can be found in southeast Asia and Africa...
and infraorder
Taxonomic rank
In biological classification, rank is the level in a taxonomic hierarchy. Examples of taxonomic ranks are species, genus, family, and class. Each rank subsumes under it a number of less general categories...
Lemuriformes. Within Lemuriformes, it belongs to the family Cheirogaleidae
Cheirogaleidae
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.-Characteristics:...
, which contains the mouse lemurs, dwarf lemur
Dwarf lemur
The dwarf lemurs are the lemurs of the genus Cheirogaleus. All of the species in this genus, like all other lemurs, are native to Madagascar.- Description :...
s, giant mouse lemur
Giant mouse lemur
The giant mouse lemurs are small lemur species in the genus Mirza. They are native to the western deciduous forests of Madagascar, usually located near the coast or other sources of water...
s, fork-marked lemurs, and hairy-eared dwarf lemur
Hairy-eared Dwarf Lemur
The hairy-eared dwarf lemur , or hairy-eared mouse lemur, is a nocturnal lemur endemic to Madagascar. It is the only member of the genus Allocebus. This species is critically endangered and the population is estimated at 100-1000 individuals. They all live a single location in the northeastern part...
. The mouse lemur genus Microcebus includes the smallest primates in the world. Phylogenetic analyses of D-loop
D-loop
In molecular biology, a displacement loop or D-loop is a DNA structure where the two strands of a double-stranded DNA molecule are separated for a stretch and held apart by a third strand of DNA. The third strand has a base sequence which is complementary to one of the main strands and pairs with...
DNA sequence
DNA sequencing
DNA sequencing includes several methods and technologies that are used for determining the order of the nucleotide bases—adenine, guanine, cytosine, and thymine—in a molecule of DNA....
s of various lemur species suggests that the gray mouse lemur may be most closely related to the reddish-gray mouse lemur
Reddish-gray Mouse Lemur
The reddish-gray mouse lemur also known as the gray-brown mouse lemur or rufous-gray mouse lemur, is found in Western Madagascar in the region around Beza Mahafaly Reserve, north to Lamboharana....
(M. griseorufus).
First described in 1777 by English illustrator John Frederick Miller
John Frederick Miller
John Frederick Miller was an English illustrator, mainly of botanical subjects.Miller was the son of the artist Johann Sebastian Müller . Miller, along with his brother James, produced paintings from the sketches made by Sydney Parkinson on James Cook's first voyage...
, M. murinus remained the only species of its genus, as well as the name used for all mouse lemurs on Madagascar, between the first major taxonomic revision in 1931 and an extensive field study conducted in 1972. The field study distinguished the brown mouse lemur, M. rufus—then considered a subspecies—as a distinct, sympatric species in the southeastern part of the island. Upon this revision, the gray mouse lemur was thought to account for all mouse lemurs that lived in the drier parts of the north, west, and south, while the brown mouse lemur represented the eastern rainforest mouse lemurs. More recently, scientific understanding of the distribution and diversity of the mouse lemurs has become much more complex. Additional field studies, genetic testing, and resulting taxonomic revisions throughout the 1990s and 2000s identified numerous new mouse lemur species, demonstrating that the genus includes at least 17 cryptic species
Cryptic species complex
In biology, a cryptic species complex is a group of species which satisfy the biological definition of species—that is, they are reproductively isolated from each other—but whose morphology is very similar ....
.
Anatomy and physiology
The gray mouse lemur shares many traits with other mouse lemurs, including soft fur, a long tail, long hind limbs, a dorsal stripe down the back (not always distinct), a short snout, rounded skull, prominent eyes, and large, membranous, protruding ears. It has large eyes and a tapetum lucidumTapetum lucidum
The tapetum lucidum is a layer of tissue in the eye of many vertebrate animals....
to enhance its vision at night. The dorsal coat is brownish-gray with various reddish tones, the flanks are light gray to beige, and the ventral fur has discrete dull beige or whitish-beige patches along portions of the belly. On the rounded face, there is a pale white patch above the nose and between the eyes; some individuals have dark orbital markings. The furred portions of the hands and feet are off-white.
The gray mouse lemur is one of the smallest primates in the world, yet it is also the largest mouse lemur. Its total length is 25 to 28 cm (9.8 to 11 in), with a head-body length of 12 to 14 cm (4.7 to 5.5 in) and a tail
Tail
The tail is the section at the rear end of an animal's body; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammals, reptiles, and birds...
length of 13 to 14.5 cm (5.1 to 5.7 in). The average weight for this species is 60 g (2.1 oz), with ranges of 58 and 67 g (2 and 2.4 oz) and 40 and 70 g (1.4 and 2.5 oz) reported. This is smaller than the world's smallest monkey, the Pygmy Marmoset
Pygmy Marmoset
The pygmy marmoset or dwarf monkey is a New World monkey native to the rainforest canopies of western Brazil, southeastern Colombia, eastern Ecuador, eastern Peru, and northern Bolivia. It is one of the smallest primates, and the smallest true monkey, with its body length ranging from...
, which ranges between 85 and 140 g (3 and 4.9 oz). Weight varies by season, with both sexes building fat reserves, up to 35% of their body weight, in the tail and hind legs prior to the dry season and periods of dormancy.
Researchers have identified differences in the tooth morphology of the first and second molar
Molar (tooth)
Molars are the rearmost and most complicated kind of tooth in most mammals. In many mammals they grind food; hence the Latin name mola, "millstone"....
s between the gray mouse lemur and the reddish-gray mouse lemur. In the reddish-gray mouse lemur, the first lower molar (m1) is squared and both the first and second upper molars (M1 and M2) have slight indentations around the middle of the posterior margin. The gray mouse lemur has a more elongated m1 and lacks the aforementioned indentation on M1 and M2. In terms of its general dentition
Dentition
Dentition pertains to the development of teeth and their arrangement in the mouth. In particular, the characteristic arrangement, kind, and number of teeth in a given species at a given age...
, the gray mouse lemur shares the same dental formula as all other members of its family, Cheirogaleidae:
This species has 66 chromosome
Chromosome
A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...
s, closely resembling the karyotype
Karyotype
A karyotype is the number and appearance of chromosomes in the nucleus of an eukaryotic cell. The term is also used for the complete set of chromosomes in a species, or an individual organism.p28...
of the dwarf lemurs (genus Cheirogaleus). Except for the X chromosome
X chromosome
The X chromosome is one of the two sex-determining chromosomes in many animal species, including mammals and is common in both males and females. It is a part of the XY sex-determination system and X0 sex-determination system...
, all chromosomes are acrocentric (with the short arm absent or virtually absent). Its genome size
Genome size
Genome size is the total amount of DNA contained within one copy of a single genome. It is typically measured in terms of mass in picograms or less frequently in Daltons or as the total number of nucleotide base pairs typically in megabases . One picogram equals 978 megabases...
is 3.12 picograms (pg).
Ecology
Like all other members of its familyFamily (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
, Cheirogaleidae
Cheirogaleidae
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.-Characteristics:...
, the gray mouse lemur is nocturnal and arboreal. It inhabits lowland tropical dry forest, sub-arid thorn scrub, gallery forest
Gallery forest
Gallery forests are evergreen forests that form as corridors along rivers or wetlands and project into landscapes that are otherwise only sparsely treed such as savannas, grasslands or deserts....
, spiny forest
Madagascar spiny thickets
The Madagascar spiny thickets is an ecoregion in Madagascar. The vegetation type is found on poor substrates with low, erratic winter rainfall. An estimated 14,000 to is covered with this habitat, all in the southwest of the country...
, eastern littoral forest, dry deciduous forest
Madagascar dry deciduous forests
The Madagascar dry deciduous forests represent a tropical dry forest ecoregion generally situated in the western part of Madagascar. The area has high numbers of endemic plant and animal species but has suffered large-scale clearance for agriculture...
s, semi-humid deciduous, moist lowland forest
Madagascar lowland forests
The Madagascar lowland forests are a tropical moist broadleaf forest ecoregion, found on the eastern coast of the island of Madagascar.-Setting:...
, transitional forest, and secondary forest
Secondary forest
A secondary forest is a forest or woodland area which has re-grown after a major disturbance such as fire, insect infestation, timber harvest or windthrow, until a long enough period has passed so that the effects of the disturbance are no longer evident...
s or degraded forests (including plantations) all ranging up to 800 m (2,624.7 ft) above sea level. The species is more common in secondary forest than in primary forest, particularly bush and scrub habitat, where it occupies a "fine branch" niche
Ecological niche
In ecology, a niche is a term describing the relational position of a species or population in its ecosystem to each other; e.g. a dolphin could potentially be in another ecological niche from one that travels in a different pod if the members of these pods utilize significantly different food...
, restricting the vertical range to fine branches, fine terminal supports, lianes
Liana
A liana is any of various long-stemmed, woody vines that are rooted in the soil at ground level and use trees, as well as other means of vertical support, to climb up to the canopy to get access to well-lit areas of the forest. Lianas are especially characteristic of tropical moist deciduous...
and dense foliage. These lemurs are usually seen on branches less than 5 cm (2 in) in diameter. The gray mouse lemur tends to prefer lower levels of the forest and the understory
Understory
Understory is the term for the area of a forest which grows at the lowest height level below the forest canopy. Plants in the understory consist of a mixture of seedlings and saplings of canopy trees together with understory shrubs and herbs...
, where branches and vegetation are dense.
In secondary forest, it is generally observed from ground level up to 10 m (32.8 ft) above ground, yet 15 to 30 m (49.2 to 98.4 ft) in the canopy of primary forest. Studies have found that the species can spend as much as 40% of its time below 3 m (9.8 ft), with 70% of its time spent at this level during the end of the dry season, when plant food is limited and insects compose a larger percentage of the diet. The species is more numerous in spiny forest, such as the Andohahela Special Reserve
Andohahela National Park
Andohahela National Park, in southeast Madagascar, is remarkable for the extremes of habitats that are representened within it. The park covers 760 square kilometers of the Anosy mountain range, the southernmost spur of the Malagasy Highlands...
, than in the gallery forest, preferring drier, littoral forest, whereas the brown mouse lemur prefers inland rain forest.
The limits of the distribution are poorly understood. It is believed to range from the Onilahy River
Onilahy River
Onilahy is a river in Toliara Province, southern Madagascar. It flows down from the hills near Betroka to the Mozambique Channel. It empties at ....
or Lake Tsimanampetsotsa
Lake Tsimanampetsotsa
Lake Tsimanampetsotsa is a saline lake in the Toliara Province, southwestern part of Madagascar. It is located at around . The lake is an important wetland and it is protected within a national park and as a Ramsar site. Ramsar site has a total area of 456.00 km² while the surface of the lake is...
in the south to Ankarafantsika National Park
Ankarafantsika National Park
Ankarafantsika National Park is a National Park in the Boeny Region of Madagascar. The closest city is Majunga 115 km north of the park. Ankarafantsika is mostly tropical in climate type. The Sakalava people are the predominate ethnic group in the park. The rodent Macrotarsomys ingens occurs only...
in the north. There is also an isolated and disjointed population in the southeastern part of the island, near Tôlanaro and the Andohahela National Park, up to the Mandena Conservation Zone. Individuals tend to occupy small home ranges of 1 to 2 ha (2.5 to 4.9 acre). The gray mouse lemur is also sympatric
Sympatric speciation
Sympatric speciation is the process through which new species evolve from a single ancestral species while inhabiting the same geographic region. In evolutionary biology and biogeography, sympatric and sympatry are terms referring to organisms whose ranges overlap or are even identical, so that...
with the reddish-gray mouse lemur, golden-brown mouse lemur, Madame Berthe's mouse lemur
Madame Berthe's Mouse Lemur
Madame Berthe's mouse lemur or Berthe's mouse lemur is the smallest of the mouse lemurs and the smallest primate in the world; the average body length is and seasonal weight is around...
, and several other cheirogaleid
Cheirogaleidae
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.-Characteristics:...
lemurs. In Ankarafantsika National Park
Ankarafantsika National Park
Ankarafantsika National Park is a National Park in the Boeny Region of Madagascar. The closest city is Majunga 115 km north of the park. Ankarafantsika is mostly tropical in climate type. The Sakalava people are the predominate ethnic group in the park. The rodent Macrotarsomys ingens occurs only...
, where it coexists with the golden-brown mouse lemur, the gray mouse lemur's relative population density
Population density
Population density is a measurement of population per unit area or unit volume. It is frequently applied to living organisms, and particularly to humans...
was highest at higher altitudes and in drier habitat, while the golden-brown mouse lemur preferred the opposite. Another study has looked at the coexistence of the gray mouse lemur and Madame Berthe's mouse lemur and found small, exclusive clusters of each species and a high degree of feeding niche overlap
Niche differentiation
The term niche differentiation , as it applies to the field of ecology, refers to the process by which natural selection drives competing species into different patterns of resource use or different niches...
.
The gray mouse lemur can reach high population densities up to several hundred individuals per square kilometer (up to 167 individuals/km2 at Ankarafantsika National Park to 712 individuals/km2 at Kirindy Mitea National Park
Kirindy Mitea National Park
Kirindy Mitea National Park is a national Park of Madagascar. It is situated in the Menabe Region.- External links :*...
). This abundance is not uniform and tends to concentrate in "population nuclei", suggesting that it is difficult to accurately estimate population densities when extrapolating from a small area (from various studies) to a large area. The difficulty in finding individuals during some times of the year, particularly during the dry periods, can further complicate the problem of estimating population densities.
Mouse lemurs are omnivorous
Omnivore
Omnivores are species that eat both plants and animals as their primary food source...
, favoring fruit and insects for the bulk of their diet. The gray mouse lemur may even come down to the ground to catch insect prey, although it will quickly return to the protective cover of the understory to consume its catch. Nectar is also a part of the gray mouse lemur's diet, making it a potential pollinator
Pollinator
A pollinator is the biotic agent that moves pollen from the male anthers of a flower to the female stigma of a flower to accomplish fertilization or syngamy of the female gamete in the ovule of the flower by the male gamete from the pollen grain...
for local plant species.
Predation
The most significant predatorPredation
In ecology, predation describes a biological interaction where a predator feeds on its prey . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of its prey and the eventual absorption of the prey's tissue through consumption...
s of the gray mouse lemur are the Madagascar long-eared owl
Madagascar Long-eared Owl
The Madagascar Owl, Asio madagascariensis, also known as the Madagascar Long-eared Owl, is a medium sized owl endemic to the island of Madagascar. It is sometimes considered to be conspecific with the Long-eared Owl, Asio otus...
and barn owl
Barn Owl
The Barn Owl is the most widely distributed species of owl, and one of the most widespread of all birds. It is also referred to as Common Barn Owl, to distinguish it from other species in the barn-owl family Tytonidae. These form one of two main lineages of living owls, the other being the typical...
. Studies conducted in Beza Mahafaly Reserve
Beza Mahafaly Reserve
The Beza Mahafaly Reserve is a nature reserve in Madagascar located northeast of Betioky Sud. The Reserve also provides training and research opportunities. It consists of a fenced gallery forest, approximately , separated by from a gallery of arid spiny forest...
and Kirindy Mitea National Park indicate a predation rate of around 25% (percent population taken by predator per year), the highest known for any primate species. However, given its high reproductive potential, predation does not appear to drastically impact its populations. Other raptors, such as the Henst's Goshawk
Henst's Goshawk
Henst's Goshawk is a species of bird of prey in the Accipitridae family.It is endemic to Madagascar. Its natural habitats are subtropical or tropical dry forests, subtropical or tropical moist lowland forests, subtropical or tropical moist montane forests, and plantations.It is threatened by...
, and owls prey upon this species. Snake
Snake
Snakes are elongate, legless, carnivorous reptiles of the suborder Serpentes that can be distinguished from legless lizards by their lack of eyelids and external ears. Like all squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales...
s, such as Ichythcyphys miniatus (a native colubrid
Colubrid
A colubrid is a member of the snake family Colubridae. This broad classification of snakes includes about two-thirds of all snake species on earth. The earliest species of the snake family date back to the Oligocene epoch. With 304 genera and 1,938 species, Colubridae is the largest snake family...
snake), Madagascar Tree Boa, as well as mammalian predators, such as the Ring-tailed Mongoose
Ring-tailed mongoose
The Ring-tailed mongoose is a euplerid that lives on the island of Madagascar. There is actually much disagreement about the placement of Madagascar's carnivores including the Ring-tailed mongoose, within the phylogenetic tree. Recent molecular work by Anne Yoder et al...
, Narrow-striped Mongoose
Narrow-striped Mongoose
The Narrow-striped Mongoose , also locally called boky-boky in Malagasy, is a member of the family Eupleridae, subfamily Galidiinae. It inhabits the dry deciduous forests of western and southwestern Madagascar...
, Fossa
Fossa (animal)
The fossa is a cat-like, carnivorous mammal that is endemic to Madagascar. It is a member of the Eupleridae, a family of carnivorans closely related to the mongoose family . Its classification has been controversial because its physical traits resemble those of cats, yet other traits suggest a...
, and Domestic Dog
Dog
The domestic dog is a domesticated form of the gray wolf, a member of the Canidae family of the order Carnivora. The term is used for both feral and pet varieties. The dog may have been the first animal to be domesticated, and has been the most widely kept working, hunting, and companion animal in...
s are also known to prey upon the gray mouse lemur. Mammalian predators often discover tree holes serving as nests and then enlarge the opening in order to obtain and eat the occupant, resulting in strong selective pressure
Evolutionary pressure
Any cause that reduces reproductive success in a proportion of a population, potentially exerts evolutionary pressure or selection pressure. With sufficient pressure, inherited traits that mitigate its effects - even if they would be deleterious in other circumstances - can become widely spread...
affecting the choice of nest hole opening diameter and deepness.
Due to its non-gregarious nature, the gray mouse lemur, like other nocturnal lemurs, primarily defends itself from predators using avoidance strategies, although group defense through the use of alarm calls and predator mobbing
Mobbing behavior
Mobbing in animals is an antipredator behavior which occurs when individuals of a certain species mob a predator by cooperatively attacking or harassing it, usually to protect their offspring. A simple definition of mobbing is an assemblage of individuals around a potentially dangerous predator...
has been observed in this species. Studies involving the placement of predator and non-predator fecal
Feces
Feces, faeces, or fæces is a waste product from an animal's digestive tract expelled through the anus or cloaca during defecation.-Etymology:...
odor with captive populations have demonstrated a genetic predisposition for predator recognition through the detection of metabolite
Metabolite
Metabolites are the intermediates and products of metabolism. The term metabolite is usually restricted to small molecules. A primary metabolite is directly involved in normal growth, development, and reproduction. Alcohol is an example of a primary metabolite produced in large-scale by industrial...
s from meat digestion. The mouse lemurs were shown to avoid locations where they typically received rewards, as well as exhibit increased activity and anti-predator behavior, when the odor of predator feces were present in that vicinity, but not when the fecal odor of Malagasy non-predators was present.
During the day, when they are most vulnerable, individuals will take shelter inside tree holes, sometimes forming nests. Between three and nine different tree holes may be used within their home range, yet individuals will utilize one particular hole for up to five consecutive days. Tree hollows tend to be preferred, but spherical constructions made of leaves are also common. Nests are usually found in tree holes with a minimum diameter of 5 cm (2 in), with a median
Median
In probability theory and statistics, a median is described as the numerical value separating the higher half of a sample, a population, or a probability distribution, from the lower half. The median of a finite list of numbers can be found by arranging all the observations from lowest value to...
of 13 cm (5.1 in), suggesting that this range in diameter of tree holes may be crucial for maintaining a healthy habitat. The gray mouse lemur also spends most of its time in dense vegetation, limiting its visibility and accessibility to predators. Furthermore, it has a high reproductive rate to counter losses to predation.
Behavior
The gray mouse lemur is nocturnal, sleeping during the day in tree holes lined with leaf litter or purpose-built spherical nests constructed from dead leaves, moss and twigs. It usually forages alone at night, but may sleep in groups during the day, the composition of which depends on gender and season. Tree holes can be shared with up to 15 other individuals, although males tend to sleep alone while females tend to share nests.All mouse lemurs are highly active at night, often scurrying like mice and leaping over 3 m (9.8 ft), using the tail as a balancing organ. When moving among the terminal branches of bushes and trees, they grip using all four feet and move with four legs. When on the ground, either to catch insects or cross short open areas, mouse lemurs hop like a frog.
Foraging behavior is often slow, with height and direction changing continuously. Predation of insects occurs primarily on the ground. Before descending, the ear pinnae move alternately to help pinpoint the precise location of their prey. Insects are captured during a rapid dash across the leaf litter and are transported by mouth up into the relative safety of the branches. Studies with captive gray mouse lemurs have shown that vision is primarily used for prey detection, although the other senses certainly play a role in foraging.
The gray mouse lemur is omnivorous, feeding primarily on fruit and invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
s. Local populations appear to specialize on locally available fruit. At both Marosalaza and Mandena, beetle
Beetle
Coleoptera is an order of insects commonly called beetles. The word "coleoptera" is from the Greek , koleos, "sheath"; and , pteron, "wing", thus "sheathed wing". Coleoptera contains more species than any other order, constituting almost 25% of all known life-forms...
s are the primary insect prey, although moths, praying mantid
Mantis
Mantis is the common name of any insect in the order Mantodea, also commonly known as praying mantises. The word itself means "prophet" in Latin and Greek...
s, fulgorid bugs, crickets, cockroaches, and spiders are also eaten. Less than half the diet consists of insects, with fruit making up a slightly larger fraction. This lemur also consumes flowers, gums and nectar from Euphorbia and Terminalia
Terminalia (plant)
Terminalia is a genus of large trees of the flowering plant family Combretaceae, comprising around 100 species distributed in tropical regions of the world. This genus gets it name from Latin terminus, referring to the fact that the leaves appear at the very tips of the shoots.Trees of this genus...
trees, leaves (Uapaca
Uapaca
Uapaca is a genus of plant, in the family Phyllanthaceae and is the only genus comprised in the subtribe Uapacinae. It comprises about 60 species, of which 49 are confined to continental Africa.-Synonyms:This genus is also known as:...
sp.), exudate
Exudate
An exudate is any fluid that filters from the circulatory system into lesions or areas of inflammation. It can apply to plants as well as animals. Its composition varies but generally includes water and the dissolved solutes of the main circulatory fluid such as sap or blood...
s (Homopteran
Hemiptera
Hemiptera is an order of insects most often known as the true bugs , comprising around 50,000–80,000 species of cicadas, aphids, planthoppers, leafhoppers, shield bugs, and others...
larvae secretions), and small vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...
s such as tree frog
Tree frog
Hylidae is a wide-ranging family of frogs commonly referred to as "tree frogs and their allies". However, the hylids include a diversity of frog species, many of which do not live in trees, but are terrestrial or semi-aquatic.-Characteristics:...
s, gecko
Gecko
Geckos are lizards belonging to the infraorder Gekkota, found in warm climates throughout the world. They range from 1.6 cm to 60 cm....
s, and chameleon
Chameleon
Chameleons are a distinctive and highly specialized clade of lizards. They are distinguished by their parrot-like zygodactylous feet, their separately mobile and stereoscopic eyes, their very long, highly modified, and rapidly extrudable tongues, their swaying gait, the possession by many of a...
s. Its diet is seasonally varied and diverse in content, giving it a very broad feeding niche, compared to other species such as the Madame Berthe's mouse lemur. Therefore it is affected more by food availability than by niche partitioning where sympatry occurs.
Dormancy
As with all members of the mouse lemur genus, the gray mouse lemur is known to enter short states of daily torpor, particularly during the cool, dry Southern HemisphereSouthern Hemisphere
The Southern Hemisphere is the part of Earth that lies south of the equator. The word hemisphere literally means 'half ball' or "half sphere"...
winter. This rare trait in primates, coupled with the ease of observing the species within its wide geographic distribution and its good representation in captivity, makes it a popular subject for research as a model organism
Model organism
A model organism is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the organism model will provide insight into the workings of other organisms. Model organisms are in vivo models and are widely used to...
.
Breeding season
The breeding season is the most suitable season, usually with favourable conditions and abundant food and water, for breeding among some wild animals and birds . Species with a breeding season have naturally evolved to have sexual intercourse during a certain time of year in order to achieve the...
. The use of alternative energy-saving strategies under the same environmental conditions was observed directly in 2008, providing the first physiological confirmation from the field. This pattern of seasonal versus daily torpor may relate to the seasonality of the region, since Kirindy is the only location west of the eastern mountain rainforests that experiences very low temperatures at night during the winter months. By entering extended torpor, sometimes referred to as hibernation, this would reduce the thermoregulatory stress in females, whereas males remain more active in preparation for the upcoming mating season. No difference in mortality has been shown between hibernating females and active males.
During torpor, the gray mouse lemur's metabolic rate slows and its body temperature drops to the ambient temperature, as low as 7 °C (44.6 °F). During the cooler months of May though August, the species selects tree holes closer to ground level, where ambient temperatures remain more stable. This allows them to remain in torpor longer, and to conserve metabolic resources.
This unusual ability for a primate to exhibit dormancy, in addition to the diminutive size, has led researchers to speculate that ancestral lemurs, and possibly ancestral primates, may have shared some traits with mouse lemurs. Consequently, the gray mouse lemur has once again been used as a model organism for studying lemur and primate evolution. For example, lemurs are thought to have colonized Madagascar by rafting
Rafting event
Oceanic dispersal is a type of biological dispersal that occurs when organisms transfer from one land mass to another by way of a sea crossing on large clumps of floating vegetation. Such matted clumps of vegetation are often seen floating down major rivers in the tropics and washing out to sea,...
to the island around 60 million years ago according to molecular phylogenetic studies. Before the discovery that ocean currents were the opposite of what they are today, thus favoring such an event, it was thought that it would have taken too long for any animal not capable of entering a state of dormancy to survive the trip. Therefore the mouse lemurs, such as the gray mouse lemur, were thought to have shared this plesiomorphic (ancestral) trait with the ancestral lemurs.
Social systems
The gray mouse lemur is described as solitary but socialSolitary but social
"Solitary but social" is a type of social organization where individuals forage separately, yet some individuals sleep in the same location or share nests. Female home ranges usually overlap while those of males do not. Males usually do not associate with other males, and male offspring are usually...
, foraging alone at night, but frequently sleeping in groups during the day. This social pattern varies by gender, season, and location. Females tend to share nests with other females and their offspring, whereas males tend to sleep alone or in pairs outside of the breeding season. Groups of females sharing a nest can be relatively stable, consisting of two to nine individuals, although a male may be found with a group of females outside the breeding season. During the breeding season (September through October), males and females may sleep in the same tree hole. Mixed sex groups can be common at this time, with single males sharing nest sites with three to seven females or single females sharing nest sites with one to three males.
Research has shown that home ranges for the gray mouse lemur are likely to be small, possibly less than 50 m (164 ft). Males typically travel further at night and have home ranges that are twice as large as those of females, often overlapping with one another, and always overlapping with at least one female's home range. Male home ranges increase threefold during the breeding season.
Female home ranges overlap less than those of males, although localized concentrations, or "population nuclei", tend to form in some areas, where the sex ratio favors females to males by three or four to one at the nucleus core. Genetic studies indicate that females arrange themselves spatially in clusters ("population nuclei") of related individuals, while males tend to emigrate from their natal group. Research has shown that females in this species may maintain smaller ranges and associate more closely with other females than in some other mouse lemur species due to a more opportunistic feeding niche and, in the case of populations at Kirindy, the use of extended, seasonal torpor.
Communication
Vocalizations and scentOlfaction
Olfaction is the sense of smell. This sense is mediated by specialized sensory cells of the nasal cavity of vertebrates, and, by analogy, sensory cells of the antennae of invertebrates...
are the primarily modes of communication within this species. Home ranges are scent marked with urine and feces. Vocalizations are complex and very high-pitched (ranging from 10 to 36 kHz
Hertz
The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....
), sometimes beyond the range of human hearing (0.02 to 20 kHz). These include calls for seeking contact, mating, distant communication, alarm, and distress.
As with other social mammals, the calls reveal the sex and identity of the individual. Dialects have also been detected between communities. The male trill call, part of the male mating display, is much like a bird song in terms of its ordered sequence of broadband frequency modulated syllables, ranging between 13 to 35 kHz in pitch
Pitch (music)
Pitch is an auditory perceptual property that allows the ordering of sounds on a frequency-related scale.Pitches are compared as "higher" and "lower" in the sense associated with musical melodies,...
and lasting 0.3 to 0.9 seconds, repeating up to 1.5 times per minute. Each locality has its own theme of trill calls that is distinct from those of neighboring communities, and resident males produce individually distinct trill calls within that theme. These calls are not genetically programmed
Genetic program
In biology, a genetic program of a cell is a physiological change brought about by a temporal pattern of activation of a particular subset of genes....
. During play, young males produce early attempts at the trill call which show high degrees of variability. Research has shown that the male mouse lemurs consciously manipulate the dialect to resemble those of their neighbors, when transferred from their home to a new neighborhood. This may reduce aggression and foster social acceptance for emigrant males as they transfer from their natal group upon maturity.
Because mouse lemurs are cryptic species, and therefore visually indistinguishable, their social calls help individuals select mates of their own species. This differentiated signaling and recognition system has promoted species cohesiveness through premating isolation, and helped researchers distinguish and identify species.
Breeding and reproduction
The mating systemMating system
A mating system is a way in which a group is structured in relation to sexual behaviour. The precise meaning depends upon the context. With respect to higher animals, it specifies which males mate with which females, under which circumstances; recognised animal mating systems include monogamy,...
is described as multi-male and multi-female. Males establish dominance hierarchies
Dominance hierarchy
A dominance hierarchy is the organization of individuals in a group that occurs when competition for resources leads to aggression...
prior to the mating season, however, some studies in the wild have shown no male aggression or visible competition for receptive females. Males in captivity become highly aggressive and form strict dominance hierarchies. These captive males may show the highest plasma
Blood plasma
Blood plasma is the straw-colored liquid component of blood in which the blood cells in whole blood are normally suspended. It makes up about 55% of the total blood volume. It is the intravascular fluid part of extracellular fluid...
testosterone
Testosterone
Testosterone is a steroid hormone from the androgen group and is found in mammals, reptiles, birds, and other vertebrates. In mammals, testosterone is primarily secreted in the testes of males and the ovaries of females, although small amounts are also secreted by the adrenal glands...
levels found in mammals, and even the odor of a dominant male can lower the testosterone levels and sexually inhibit a subordinate male. During the breeding season, male testes
Testicle
The testicle is the male gonad in animals. Like the ovaries to which they are homologous, testes are components of both the reproductive system and the endocrine system...
increase significantly in size, facilitating sperm competition
Sperm competition
Sperm competition is a term used to refer to the competitive process between spermatozoa of two different males to fertilize an egg of a lone female. Competition occurs whenever females engage in promiscuous mating to increase their chances in producing more viable offspring...
due to female promiscuity. Studies with the gray mouse lemur have shown that the optimal insemination period, during which a male is most likely to sire offspring, occurs early during a female's receptivity. Only during the mating season does male mortality rise above that of female mortality.
The females are receptive for 45 to 55 days between September and October, with estrus
Estrous cycle
The estrous cycle comprises the recurring physiologic changes that are induced by reproductive hormones in most mammalian placental females. Estrous cycles start after puberty in sexually mature females and are interrupted by anestrous phases or pregnancies...
lasting 1 to 5 days. Females advertise estrus by distinctive high-frequency calls and scent-marking. Gestation lasts 54 to 68 days, averaging 60 days, typically resulting in 2 or 3 offspring weighing 5 g (0.17636981052556 oz) each. Infants are born in a leaf nest or tree hole in November prior to the onset of the rainy season. Weaning
Weaning
Weaning is the process of gradually introducing a mammal infant, either human or animal, to what will be its adult diet and withdrawing the supply of its mother's milk.The process takes place only in mammals, as only mammals produce milk...
occurs after 25 days, and the infants are either left in the nest or carried in the mother's mouth and deposited on a branch while she forages. Infant mouse lemurs do not cling to the mother's fur. Independence is attained in 2 months, while sexual maturity is reached at 10 to 29 months in females and 7 to 19 months in males. Closely related females remain loosely associated after maturation (female philopatry
Philopatry
Broadly, philopatry is the behaviour of remaining in, or returning to, an individual's birthplace. More specifically, in ecology philopatry is the behaviour of elder offspring sharing the parental burden in the upbringing of their siblings, a classic example of kin selection...
), whereas males disperse from their natal area. In the wild, the gray mouse lemur's reproductive lifespan is no more than 5 years, although captive specimens have reportedly lived as long as 15 years and 5 months.
Conservation status
The gray mouse lemur was listed in Appendix 1 by the Convention on International Trade in Endangered Species (CITES) in 1975, declaring it as threatened with extinction and prohibiting international trade of specimens except for non-commercial use, such as scientific research. As of 2009, the species was no longer listed under Appendix 1. The 2008 International Union for Conservation of Nature (IUCN) Red List assessment lists it as a species of Least ConcernLeast Concern
Least Concern is an IUCN category assigned to extant taxon or lower taxa which have been evaluated but do not qualify for any other category. As such they do not qualify as threatened, Near Threatened, or Conservation Dependent...
(LC) with a decreasing population trend. Its greatest threats are habitat loss from slash-and-burn agriculture
Slash and burn
Slash-and-burn is an agricultural technique which involves cutting and burning of forests or woodlands to create fields. It is subsistence agriculture that typically uses little technology or other tools. It is typically part of shifting cultivation agriculture, and of transhumance livestock...
and cattle-grazing
Grazing
Grazing generally describes a type of feeding, in which a herbivore feeds on plants , and also on other multicellular autotrophs...
, as well as live capture for the local pet trade in the northern and southern parts of its range. Although this species inhabits secondary forests, studies have shown that decreased habitat quality adversely affects its populations since fewer tree holes offer fewer opportunities to conserve energy, increasing stress and mortality. Studies in the late 1960s and 1970s showed that heavy logging between 1968 and 1970 seemed to result in decreased body weight, the use of smaller trees for nesting sites, and a smaller maximum female nesting group size (down to 7 from 15). There is also a concern that although daily torpor can help conserve energy and resources during moderate food shortages, extended food shortages brought about by climate change
Climate change
Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions or the distribution of events around that average...
could create too much stress and severely impact the survivability of the species.
The gray mouse lemur is considered to be one of Madagascar's most abundant small native mammals, found in seven national parks, five special reserves, the Berenty Private Reserve
Berenty Reserve
Berenty Reserve is a small private reserve of gallery forest along the Mandrake river, set in the semi-arid spiny forest ecoregion of the far south of Madagascar. For more than three decades the primatologist Alison Jolly , researchers and students have visited Berenty to conduct fieldwork on lemurs...
, and other privately protected forests within the Mandena Conservation Zone.
This species of mouse lemur breeds very well in captivity, although it is not commonly displayed in zoos like some larger, diurnal lemurs. In 1989, more than 370 individuals were housed by 14 International Species Information System
International Species Information System
-External links:*...
(ISIS) and non-ISIS institutions across the United States and Europe, 97% of which were captive born. In March 2009, 167 were registered at 29 ISIS institutions, including the Duke Lemur Center
Duke Lemur Center
The Duke Lemur Center is an sanctuary for rare and endangered prosimian primates, located at Duke University in Durham, North Carolina. It is the largest sanctuary for prosimian primates in the world....
.