(Cheirogaleidae)
Class: Mammalia
Order: Primates
Suborder: Prosimii
Family: Cheirogaleidae
Thumbnail description
Dwarf and mouse lemurs are the smallest of the Madagascar lemurs, with colors ranging from gray to dark brown dorsally and cream to yellowish brown ventrally; some have conspicuous facial markings (e.g., dark rings around the eyes; pale nose stripe)
Size
Head and body length, 5–11 in (12–27 cm); weight 1–16.5 oz (30–460 g)
Number of genera, species
5 genera, 17 species
Habitat
Members of this family are found throughout Madagascar in all forest types; all species are nocturnal and essentially arboreal
Conservation status
Endangered: 3 species; Vulnerable: 1 species; Lower Risk/Near Threatened: 1 species
Distribution
Restricted to forested regions of Madagascar
Evolution and systematics
There is no fossil record in Madagascar for any lemurs, although mouse lemur skulls have been reported among subfossils from sites just a few thousand years old. An Eocene primate from Pakistan, Bugtilemur, shows some similarities to modern dwarf lemurs (Cheirogaleus) in molar tooth morphology and was therefore allocated to the family Cheirogaleidae by its discoverers.
Chromosomal and molecular evidence overwhelmingly indicates that lemurs are a monophyletic group (i.e., all derived from a specific common ancestor), thus resolving a conflict in interpretation of morphological characters. At one time, numerous authors suggested that the dwarf and mouse lemurs (Cheirogaleidae) are closer to the loris group (Lorisiformes) than to other lemurs, but this has now been effectively discounted. Within the adaptive radiation of the Madagascar lemurs, it is equally clear that dwarf and mouse lemurs belong to a monophyletic subgroup, derived from a later common ancestor retaining many primitive features from the earliest lemurs. While chromosomal and molecular evidence indicates that the aye-aye (Daubentonia) branched away first during diversification of the lemurs, relationships between the remaining four families (Cheirogaleidae, Lemuridae, Lepilemuridae, Indriidae) remain unresolved, probably because they separated from one another relatively quickly.
Physical characteristics
These are the smallest lemurs, ranging in size from 1 oz (30 g) for the pygmy mouse lemur (Microcebus berthae) to 16.5 oz (460 g) for the fork-crowned lemur (Phaner furcifer). All species are nocturnal, with correspondingly large eyes, and essentially arboreal, with relatively long tails. The tarsal bones in the heel region of the foot are mildly elongated. The fur is dense and woolly in all species. As a general rule, species inhabiting the eastern rainforest tend to be rufous (reddish brown) in dorsal coloration, while those living in the dryer forests in the west are grayer. In all species, the ventral fur is considerably lighter and varies from white through cream to yellowish brown. The external ears (pinnae) are relatively large and, in some species, very conspicuous.
Distribution
Species of the genera Cheirogaleus and Microcebus occur throughout the forested regions of Madagascar, while the hairy-eared mouse lemur (Allocebus), Coquerel's lemur (Mirza), and fork-crowned lemurs (Phaner) have more restricted ranges.
Habitat
All species are essentially arboreal and use nests of some kind. Mouse lemurs (Microcebus and Mirza) construct globular leaf-nests but can also use tree hollows, whereas dwarf lemurs (Cheirogaleus), hairy-eared mouse lemurs, and fork-crowned lemurs typically use tree hollows.
Dwarf and mouse lemurs are found in every kind of forested habitat in Madagascar, including evergreen rainforest in the east, deciduous forest in the northwest and west, and semiarid forest in the southwest and south. Mouse lemurs (Microcebus species) also occur in small patches of scrub vegetation and even in gardens in settled areas.
Behavior
Although they typically forage alone at night, all species in the family Cheirogaleidae live in social networks involving overlapping ranges, occasional contacts during the night, and nest sharing during the day. However, the degree of tolerance between same-sex adults varies, such that some species (e.g., mouse lemurs) live in dispersed multi-male/multi-female groups, while others (e.g., dwarf lemurs) live in dispersed monogamous groups.
Because all species are typically solitary while foraging, social communication during the night is mainly based on vocalizations and scent marking. Due to their small body sizes, most vocalizations are relatively high-pitched and the small-contact, alarm, threat, and range defense. According to species, scent marking can involve deposition of urine, feces, or secretions of special skin glands.
All species show some degree of home-range defense between adults of each sex, but only those that are clearly monogamous (Cheirogaleus) or that show a tendency to monogamy (Mirza and Phaner) defend an exclusive territory.
All dwarf and mouse lemurs are exclusively nocturnal. Smaller species show incomplete control of body temperature, which declines during daytime sleep, and varying degrees of torpor, ranging from facultative to obligatory. Fat may be stored in the tail during the rainy season as a reserve for torpor during the dry season.
Feeding ecology and diet
Fruits and insects are the staple diet for most dwarf and mouse lemurs, but each species shows a particular specialty, sometimes involving plant exudates (gums). Whereas dwarf lemurs feed mainly on fruits, mouse lemurs tend to eat a relatively balanced diet of fruits and insects. However, Coquerel's mouse lemur also consumes secretions produced by insects as part of its diet. Gum-feeding occurs to a limited extent in both
Cheirogaleus and Microcebus species, but fork-crowned lemurs are heavily specialized on this food source as the main dietary intake. Some species also feed on nectar from flowers (e.g., Cheirogaleus and Phaner).
Most species tend to concentrate foraging activity for fruits and insects in the fine branches of trees and bushes, but fork-crowned lemurs spend much time on tree trunks searching for gums.
As an adaptation to gum-feeding, fork-crowned lemurs have a particularly well-developed tooth comb in the lower jaw. They also have sharply pointed tips (needle-claws) on the nails of all digits, except the big toe, for clinging to broad trunk surfaces while feeding on gums. The caecum (located at the extreme of the colon) is enlarged in Phaner as an adaptation for digestion of gum assisted by symbiotic bacteria. The presence of needle-claws in the hairy-eared mouse lemur suggests that this species also feeds regularly on gums.
Reproductive biology
In all dwarf and mouse lemurs, females show a clear-cut brief period of estrus. In the smaller species, a membrane seals the vulva most of the time. Estrus is marked by the swelling and opening of the vulva, and in some species a vaginal plug is formed after mating. Males actively pursue estrous females in the trees, and in most or all species the male emits a specific mating call. In species with a multi-male/multi-female social system (e.g., Microcebus species), several males can mate with a female during estrus, and genetic tests have shown that different fathers may sire offspring in the same litter. The gestation period, lasting between two and three months according to species, is relatively short compared to other primates. All species typically rear their offspring in a nest. The smaller dwarf and mouse lemurs have multiple litters commonly containing two to three offspring, whereas the larger species usually have a single offspring. Suckling occurs relatively frequently during the night, so mothers must reduce their activity away from the nest for some weeks after birth. Strictly seasonal breeding is found in all species. Births typically take place during the wet season (October–March).
Conservation status
At one time all lemurs were classified as Endangered and as a result all are included in Appendix I of the CITES legislation. However, some mouse lemurs (e.g., Microcebus murinus, M. rufus) are in fact very widespread in Madagascar, occurring in all kinds of habitats, including domestic gardens. However, two mouse lemur species with very restricted ranges are listed as Endangered (M. berthae and M. ravlobensis). Most dwarf lemurs are also quite widespread, although less common than M. murinus and M. rufus species. Species in the remaining genera (Allocebus, Mirza, and Phaner) all have much more restricted geographical distributions. Allocebus trichotis is listed as Endangered, Mirza coquereli as Vulnerable, and Phaner furcifer as Near Threatened.
Significance to humans
Dwarf and mouse lemurs are all too small to be of much significance to humans. They may occasionally be eaten, but the amount of meat obtained is generally too limited to make targeted hunting worthwhile, with the possible exception of fork-crowned lemurs.
Species accounts
Hairy-eared mouse lemurGreater dwarf lemur
Western fat-tailed dwarf lemur
Gray mouse lemur
Red mouse lemur
Coquerel's mouse lemur
Masoala fork-crowned lemur
Resources
Books:Charles-Dominique, et al., eds. Nocturnal Malagasy Primates. New York: Academic Press, 1980.
Groves, Colin P. The Taxonomy of Primates. Washington, DC: Smithsonian Institution Press, 2001.
Martin, Robert D. Primate Origins and Evolution: A Phylogenetic Reconstruction. New Jersey: Princeton University Press, 1990.
Sussman, Robert W. Primate Ecology and Social Structure. Volume 1: Lorises, Lemurs and Tarsiers. Needham Heights, MA: Pearson Custom Publishing, 1999.
Tattersall, Ian. The Primates of Madagascar. New York: Columbia University Press, 1982.
Periodicals:Atsalis, Sylvia. "Diet of the Brown Mouse Lemur (Microcebus rufus) in Ranomafana National Park, Madagascar." International Journal of Primatology 20 (1999): 193–229. ——. "Seasonal Fluctuations in Body Fat and Activity Levels in a Rain Forest Species of Mouse Lemur (Microcebus rufus)." International Journal of Primatology 20 (1999): 883–910.
Fietz, Joanna. "Monogamy As a Rule Rather Than Exception in Nocturnal Lemurs: The Case of the Fat-tailed Dwarf Lemur, Cheirogaleus medius." Ethology 105 (1999): 259–272.
Fietz, Joanna, and Jürg U. Ganzhorn. "Feeding Ecology of the Hibernating Primate Cheirogaleus medius: How Does It Get So Fat?" Oecologia 121 (1999): 157–164.
Kappeler, Peter M. "Intrasexual Selection in Mirza coquereli: Evidence for Scramble Competition Polygyny in a Solitary Primate." Behavioral Ecological Sociobiology 41 (1997): 115–127.
Marivaux, Laurent, et al. "A Fossil Lemur from the Oligocene of Pakistan." Science 294 (2001): 587–591.
Martin, Robert D. "Adaptive Radiation and Behaviour of the Malagasy Lemurs." Philosophical Transactions of the Royal Society of London Series B 264 (1972): 295–352.
Meier, Bernhard, and Roland Albignac. "Rediscovery of Allocebus trichotis Günther 1875 (Primates) in Northeast Madagascar." Folia Primatologica 56 (1991): 57–63.
Müller, Alexandra E. "A Preliminary Report on the Social Organization of Cheirogaleus medius (Cheirogaleidae; Primates) in North-West Madagascar." Folia Primatologica 69 (1998): 160–166. ——. "Aspects of Social Life in the Fat-tailed Dwarf Lemur (Cheirogaleus medius): Inferences from Body Weights and Trapping Data." American Journal of Primatology 49 (1999): 265–280.
Radespiel, Ute. "Sociality in the Gray Mouse Lemur (Microcebus murinus) in Northwestern Madagascar." American Journal of Primatology 51 (2000): 21–40.
Radespiel, Ute, et al. "Sex-specific Usage Patterns of Sleeping Sites in Grey Mouse Lemurs (Microcebus murinus) in Northwestern Madagascar." American Journal of Primatology 4 (1998): 77–84.
Schmid, Jutta. "Sex-specific Differences in Activity Patterns and Fattening in the Gray Mouse Lemur (Microcebus murinus) in Madagascar." Journal Mammalia 80 (1999): 749–757.
Yoder, Anne D. "Relative Position of the Cheirogaleidae in Strepsirhine Phylogeny: A Comparison of Morphological and Molecular Methods and Results." American Journal of Physical Anthropology 94 (1994): 25–46. ——. "Back to the Future: A Synthesis of Strepsirrhine Systematics." Evolutionary Anthropology 6 (1997): 11–22.
Yoder, Anne D., et al. "Ancient Single Origin for Malagasy Primates." Proceedings of the National Academy of Sciences of the United States of America 93 (1996): 5122–5126.
[Article by: Robert D. Martin, PhD]
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