Cheirogaleidae
dwarf lemurs and mouse lemurs
(Also: fork-marked lemur)

There are 21 species in 5 genera in the family Cheirogaleidae. As with most Malagasy mammals, recent research has resulted in the naming of several new species in recent years. These are the smallest lemur species and are all arboreal, nocturnal, and social. They are all similar in ecology, with relatively restricted ranges and some variation in diets. (Groves, 1989; Martin, 2003; Nowak and Paradiso, 1983; Thorington and Anderson, 1984; Vaughan, et al., 2000)

Dwarf and mouse lemurs are restricted to forested regions of Madagascar. (Martin, 2003; Nowak and Paradiso, 1983; Vaughan, et al., 2000)

Dwarf and mouse lemurs are found in forested habitats of different types, including evergreen, deciduous, and scrub forests. Mouse lemurs (Microcebus) are also found in suburban and agricultural areas. Dwarf and mouse lemurs rest during the day in tree hollows or rounded leaf nests in Microcebus and Mirza species. (Martin, 2003; Nowak and Paradiso, 1983; Vaughan, et al., 2000)

Dwarf and mouse lemurs are the smallest lemurs, from 12 to 27 cm in length and 30 (Microcebus berthae) to 460 g (Phaner furcifer). Pygmy, or Berthe's, mouse lemurs (Microcebus berthae) are the smallest primates. Cheirogaleids have gray or brown dorsal pelage and lighter, creamy or yellowish pelage on their ventral surfaces. Some species have bold markings on their faces, such as eye rings or nose stripes. The fur is often thick and woolly. In general species in eastern Madagascar (more mesic forests) have reddish or brown fur and species in western Madagascar (more arid forests) have grayish fur. Dwarf and mouse lemurs are characterized by unusually long tails, ranging from about the length of the body to roughly half again as long; large, thin, and membranous ears; and well developed facial and carpal vibrissae. They have large, forward-facing eyes, reflecting their nocturnal lifestyle, compact bodies, and long, delicate fingers with rounded tips. In many species males are slightly larger than females. (Martin, 2003; Nowak and Paradiso, 1983; Vaughan, et al., 2000)

Their hind feet have elongated calcaneus and navicular bones. As with other strepsirhines, they have a distinctive " toilet claw" on the second digit of their hind feet. Their thumb (pollex) is not as conspicuously separated from the other digits as in lemurs; and the third and fourth digits of both feet are similar in length. (Feldhamer, et al., 1999; Groves, 1989; Nowak and Paradiso, 1983; Szalay and Dodson, 1979; Thorington and Anderson, 1984; Vaughan, et al., 2000)

Cranially, dwarf and mouse lemurs are defined by details of their cranial circulation and bullae. The frontal and palatal bones contact the orbit in most cheirogaleids. They have the typical strepsirhine tooth comb made up of lower incisors and canines, and their dental formula is 2/2, 1/1, 3/3, 3/3 = 36. In contrast to lemurs, their upper incisors are elongate. Hypocones are small are absent on the upper molars. (Feldhamer, et al., 1999; Groves, 1989; Nowak and Paradiso, 1983; Szalay and Dodson, 1979; Thorington and Anderson, 1984; Vaughan, et al., 2000)

Some species are generally found in monogamous family groups (Cheirogaleus, Phaner, Mirza). Microcebus species occur in multi-male, multi-female social groups in which males pursue females when they are in estrous. Males use mating calls during the time of breeding. Females can have multiple male mates and give birth to litters with multiple paternity as a result. Females have distinct estrous cycles. In some species the vagina is sealed with a membrane when the female is not in estrous. A vaginal plug forms after copulation in some species. Estrous is signaled by swelling of the vulva. (Martin, 2003; Nowak and Paradiso, 1983; Vaughan, et al., 2000)

Dwarf and mouse lemurs breed seasonally, generally during the wet season from October to March. Smaller species can have multiple litters in a year, each with 2 to 3 young, larger species give birth to single offspring. Gestation is from 2 to 3 months and the young are cared for in a nest. (Martin, 2003; Nowak and Paradiso, 1983; Vaughan, et al., 2000)

Females nurse their young regularly throughout the day, making it necessary for them to return to the nest throughout their nighttime foraging period. (Martin, 2003)

Dwarf lemurs (Cheirogaleus) have been recorded living up to 23.2 years old and fork-marked lemurs (Phaner furcifer) have been recorded living up to 25 years in captivity. Longevity in the wild has not been well documented and is likely to be shorter than captive lifespans.

Dwarf and mouse lemurs are all nocturnal and arboreal. They generally forage on their own, but roost during the day in small social groups and re-connect with other members of their social groups periodically throughout the night. Social organization varies among species, with some species (Microcebus, for example) being found in multi-male, multi-female groups and others (Cheirogaleus, for example) occurring in monogamous family units. Multi-male, multi-female groups are relatively loosely structured, with individuals having overlapping home ranges. Species that occur in relatively monogamous family units may cooperate to defend territories. Smaller species may become torpid occasionally and their body temperatures are labile, lowering when they sleep and rising when active. Fat is stored in the tail during rainy seasons to help individuals make it through dry seasons or times of torpor. Cheirogaleus species in arid habitats may aestivate for up to 6 months. Cheirogaleids get around with bipedal leaps and quadrupedal locomotion on branches. (Martin, 2003; Nowak and Paradiso, 1983; Vaughan, et al., 2000)

Individuals in social groups communicate with each other through scent marking and vocalizations. Scent marking involves leaving urine, feces, and gland secretions on trees and branches. Vocalizations include contact calls, alarm calls, and territorial defense calls, most are relatively high pitched sounds. (Martin, 2003)

Dwarf and mouse lemurs are generally omnivorous, eating fruits, insects, nectars, plant gums, and occasionally leaves and small vertebrates. Some species specialize on portions of that diet. For example, Cheirogaleus species eat mainly fruit and Phaner species specialize on plant gums and have a well-developed tooth comb in the lower jaw for this purpose. Most species forage mainly on the small branches of trees and shrubs below 10 m high, but they also forage on tree trunks, especially Phaner species, which have sharp claws on their digits to allow clinging to vertical surfaces. Phaner species also have an enlarged caecum to help them digest plant gums. (Martin, 2003; Nowak and Paradiso, 1983; Vaughan, et al., 2000)

Predators of cheirogaleids are not reported in the literature, but are likely to include nocturnal predators, such as snakes (Serpentes), owls (Strigiformes), and fossas (Cryptoprocta ferox). They are nocturnal, cryptically colored, arboreal, and agile, all helping to decrease their vulnerability to predators. (Vaughan, et al., 2000)

Through their frugivory, cheirogaleids may help to disperse seeds. They also impact insect populations through predation.

Dwarf and mouse lemurs are too small to be hunted for food to a great extent. They may help to disperse seeds in forests and control insect pests to some extent. (Martin, 2003; Nowak and Paradiso, 1983)

There are no adverse effects of dwarf and mouse lemurs on humans.

Most dwarf and mouse lemur species are considered "data deficient" by the IUCN, primarily because many species are newly named and poorly understood. Of the 29 species recognized by the IUCN, 14 species are data deficient, 7 are least concern, 1 is near threatened, 2 are vulnerable, and 4 are endangered. Species considered least concern are still considered potentially vulnerable to habitat destruction and populations are thought to be in decline. Smaller species tend to be more common and widespread, larger species tend to have fragmentary distributions and are less common, therefore more threatened. Previously, all lemurs were considered endangered, so they are all listed on Appendix I of CITES. (IUCN, 2009; Martin, 2003)

Hairy-eared dwarf lemurs (Allocebus trichotis) were considered extinct until they were rediscovered in 1989. (Vaughan, et al., 2000)

There are no Cheirogaleidae fossils, although they are known from subfossil deposits on Madagascar. An Eocene fossil genus from Pakistan, Bugtilemur, is considered part of Cheirogaleidae. (Martin, 2003)