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Allocebus trichotishairy-eared dwarf lemur

By Chad Drury

Geographic Range

Hairy-eared dwarf lemurs, Allocebus trichotis, are unquestionably among the rarest of surviving lemurs, and presumably have never existed in high numbers. Allocebus trichotis had not been seen in over 20 years when, in March 1989, it was rediscovered in the vicinity of the Mananara River in northeastern Madagascar, which is its exclusive habitat. Until its rediscovery, it was only known from five museum specimens. Its distribution on the island is isolated to the northeastern portion, 16°12’S, 49°37’E through 16°28’S, 49°38’E. (Albignac and Meier, 1991)

Habitat

Little in known about the habitat preferences of A. trochotis, but it appears to occur mainly in lowland primary forest. This species is found at elevations between 680 and 1235 m. (Albignac and Meier, 1991)

  • Range elevation
    680 to 1235 m
    2230.97 to 4051.84 ft

Physical Description

Allocebus trichotis has an average head and body length of 133 mm and an average tail length of 170 mm. Mass ranges between 70 and 100 g, with an average of 85 g. Males and females are similar in size and coloration.

The dorsal surface of these animals is brownish gray, the underparts are whitish gray, and the tail is reddish brown. The ears are short, with tufts of long hair in front and on the internal side of the lobe, hence the common name Hairy-eared Dwarf Lemur.

This species has teeth like Phaner fucifer (forked-crown lemurs), but the teeth are unique in that the second and third upper molars are caniniform and the first upper incisor is enlarged. On the digits the nails are keeled, not pointed.

Hairy-eared dwarf lemurs have a relatively long tongue compared to Microcebus and Cheirogaleus. (Albignac and Meier, 1991)

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    70 to 100 g
    2.47 to 3.52 oz
  • Range length
    125 to 145 mm
    4.92 to 5.71 in

Reproduction

Allocebus trichotis is presumed to be monogamous. The only social grouping that is seen consistently is that of a male, a female, and a single offspring. This points to a monogamous mating system. (Albignac and Meier, 1991; Nowak, 1999)

Nothing reliable is known about reproduction in wild A. trichotis. Groups of male, female and a single young have been seen, indicating that one young is born per pregnancy. Groups of juveniles half the size of adults have been recorded nesting in one tree hole in the month of March. This supports the interpretation that estrus occurs at the beginning of the wet season in November to December with births occurring in January to February, if gestation periods are approximately 2 months as in Microcebus and Cherigaleus. (Albignac and Meier, 1991; Nowak, 1999)

  • Breeding interval
    The breeding interval of these primates is unknown.
  • Breeding season
    Breeding appears to occur from January to February.
  • Average number of offspring
    1
  • Average gestation period
    2 months

Females care for and nurse their young in a tree nest until the young have reached independence. The length of dependency is unknown. Because the species is apparently monogamous, males may play a role in care of the young, including grooming, protecting, or carrying. However, data on male parental behavior are lacking, so these possibilities are only speculative. (Nowak, 1999; Nowak, 1999)

  • Parental Investment
  • altricial
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female
  • pre-independence
    • provisioning
      • female
    • protecting
      • female
  • extended period of juvenile learning

Lifespan/Longevity

There are no data on lifespan or longevity for this species. However, other members of the family Cheirogaleidae are noted to live 15 to 19 years in captivity. Allocebus trichotis is probably similar. (Nowak, 1999)

Behavior

Allocebus trichotis is a nocturnal species, becoming active at dusk and remaining so until dawn, and is primarily arboreal. Allocebus trichotis makes nests of fresh leaves in small holes in either living or dead trees, usually 3 to 5 meters above the ground. Local people report that up to six animals may sleep together, both male and female plus juveniles. The basic group of hairy-eared dwarf lemurs is comprised of an adult pair and their offspring. They have been reported to hibernate, becoming torpid in trees or under leaf litter at the base of a tree from May to September. During this torpid season A. trichotis utilizes fat distributed across the body and stored for this purpose (Charles-Dominique et al, 1980).

Mated pairs groom one another, removing dead skin and parasites. In captive hairy-eared dwarf lemurs it was found that males and females groom each other before they leave the nest at night (Nowak, 1999). (Albignac and Meier, 1991; Charles-Dominique, et al., 1980; Nowak, 1999)

Home Range

The size of the home range used by these animals is not known.

Communication and Perception

Specific patterns of communication have not been reported for A. trichotis. However, if this species is like other primates, some combination of vocal communication, body postures, and tactile communication are used in interacions with conspecifics. These aniamls may also use chemical communication. (Nowak, 1999)

Food Habits

No data are available detailing what A. trichotis eats in the wild. Allocebus trichotis has large upper incisors, like those of Phaner, and may use these teeth to scrape tree bark to obtain exudates or plant gum, as does Phaner species. In captivity, 50 to 70% of the diet consists of small to medium sized locusts, which are caught by jumping on them and grasping them with both hands. These actions are very stereotypical and look as if they may be part of a fixed action pattern.

In addition to insects, A. trichotis may be adapted to eating nectar. The animal has an extraordinarily long tongue and readily ate honey while in captivity (Nowak, 1999). (Albignac and Meier, 1991; Nowak, 1999)

  • Animal Foods
  • insects
  • Plant Foods
  • nectar
  • sap or other plant fluids

Predation

Allocebus trichotis functions very well in its arboreal environment. With its small size it is able to out-climb most predators. Although data on predation rates are not available, likely predators include Malagasy carnivores (Eupleridae), owls, and humans.

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

If A. trichotis feeds on nectar, as has been suggested, this species may play some role in plant pollination. These animals may also act to control insect populations somewhat. To the extent that they serve as prey items, these animals may impact predator populations.

Economic Importance for Humans: Positive

Hairy-eared dwarf lemurs are reportedly eaten regularly by the local people of Northeastern Madagascar.

  • Positive Impacts
  • food

Economic Importance for Humans: Negative

There are no known adverse affects of A. trichotis on humans.

Conservation Status

Little is known about the conservation status of A. trichotis, because individuals of this species are extremely hard to locate. Since 1875, biologists have observed speciments only twice--in 1966 and 1989. It is certain that the rapid deforestation and destruction of habitat are the main contributing factors to the decline of A. trichotis. Efforts of the Malagasy government are now underway to protect one of the last portions of virgin lowland rainforest in Northeastern Madagascar. This action and continuing research are vital to study the conservation status and basic biology of this species in the wild. (Albignac and Meier, 1991; Harcourt, 1990; Nowak, 1999)

Other Comments

Most lemurs on the island of Madagascar are endangered. Rapid deforestation and the exponential growth rate of humans gives these species little room. Hairy-eared dwarf lemurs are at particular risk and are classified as endangered by CITES. Populations of A. trichotis are severely fragmented and are known to exist in no more than 5 locations. Habitat preservation is needed to aid the survival of this species and all others on the island of Madagascar.

Contributors

Nancy Shefferly (editor), Animal Diversity Web.

Chad Drury (author), University of Northern Iowa, Jim Demastes (editor), University of Northern Iowa.

Glossary

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map

acoustic

uses sound to communicate

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

arboreal

Referring to an animal that lives in trees; tree-climbing.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

food

A substance that provides both nutrients and energy to a living thing.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

island endemic

animals that live only on an island or set of islands.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

omnivore

an animal that mainly eats all kinds of things, including plants and animals

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

tactile

uses touch to communicate

terrestrial

Living on the ground.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

References

Albignac, R., B. Meier. 1991. Rediscovery of *Allocebus trichotis* Gunther 1875 (Primates) in Northeast Madagascar. Folia Primatol, 56: 57-63.

Charles-Dominique, P., H. Cooper, G. Pariente, A. Petter-Rousseaux, A. Schilling. 1980. Nocturnal Malagasy Primates, Ecology, Physiology and Behavior. New York: Academic Press.

Harcourt, C. 1990. Lemurs of Madagascar and the Comoros. The IUCN Red Data Book. Gland, Switzerland: IUCN.

Nowak, R. 1999. Walker's Mammals of the World, Sixth Edition. Baltimore and London: The Johns Hopkins University Press.

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