Eastern Woolly Lemur (Avahi laniger)


MORPHOLOGY:
The average body mass for this species has a range from 900 to 1200 grams (Ganzhorn et al., 1985). The lower second and third molars of males are larger than females and the skulls of males are slightly wider than females (Gingerich and Ryan, 1979), but for the most part this species is not sexually dimorphic. The lower incisors have been modified in this species to form a tooth comb which is used in grooming (Gingerich and Ryan, 1979). The upper incisors are reduced as compared to anthropoid primates (Gingerich and Ryan, 1979). The dental formula for this species is 2:1:2:3 on the upper jaw and 2:0:2:3 on the lower jaw (Ankel-Simons, 2000). This species has a pelage color that is gray-brown to olivaceous red-brown dorsally and gray ventrally (Tattersall, 1982). The tail is a rusty red color that darkens distally (Tattersall, 1982). There is a pale transverse band across the forehead, with the throat and sometimes the cheeks also being pale (Tattersall, 1982).

RANGE:
This species is found on the island of Madagascar, and lives in the coastal rainforests.

The Eastern woolly lemur is found in the following reserves in Madagascar (Harcourt and Thornback, 1990):
ECOLOGY:
This is primarily a folivorous species. Only parts of the leaf blade and not the midrib or petiole are fed upon (Ganzhorn et al., 1985). The leaves eaten generally are immature although mature leaves are consumed (Ganzhorn et al., 1985). The leaves consumed were found not to contain any alkaloids (Ganzhorn et al., 1985). In the species of plants consumed the leaves contain high concentrations of protein and sugar (Ganzhorn et al., 1985). At Ranomafana the most frequent species eaten for leaves is Haronga madagascariensis (Harcourt, 1991). Flowers and fruits are occasionally fed upon (Ganzhorn et al., 1985). The species Erythroxylum sp. was eaten for its flowers by this species and the fruit of Rheedia was also found to have been eaten (Ganzhorn et al., 1985). Feeding for this species occurs most often in the two hours after dusk and the two hours before dawn (Harcourt, 1988). Feeding for this species takes place at the top and the periphery of trees (Ganzhorn et al., 1985). When moving in feeding trees this species most often uses thin branches less than 3 centimeters in diameter (Ganzhorn et al., 1985). Large trunks are used to support the weight of an individual when feeding upon a small tree that can not support the individual's weight (Ganzhorn et al., 1985). Feeding heights range from 2 to 9 meters (Ganzhorn et al., 1985). The Eastern woolly lemur spends a large part of its time resting (Harcourt, 1987). This species probably rests so long during the night so as to conserve energy due to the fact that the majority of the diet is composed of leaves that are not as energy rich as other food sources (Ganzhorn et al., 1985). At Ranomafana it was found that resting occupied 59.5% of the nights activities, grooming 5%, traveling 13.5%, and feeding 22% (Harcourt, 1991). Where the Eastern woolly lemur is sympatric with Lepilemur sp., which is also a folivore, it displaces it from the better quality food sources (Ganzhorn, 1993). This species sleeps during the day in the center-bottom part of the crown of trees that have dense foliage and at a height of 2 to 9 meters (Ganzhorn et al., 1985). During the night this species rests in the center of tree crowns or on lianas below the canopy at heights from 2 to 10 meters (Ganzhorn et al., 1985). This is a nocturnal species which probably evolved from a diurnal ancestor (Ganzhorn et al., 1985).

The Eastern woolly lemur has been found to be preyed upon by Henst's goshawk, Accipiter henstii (Goodman et al., 1998). This species may be susceptible to diurnal raptors due to that it sleeps on relatively exposed tree trunks in a clinging position, and Henst's goshawk rests on exposed branches scanning the forest for prey (Goodman et al., 1998).

LOCOMOTION:
The avahi is a vertical leaper. The Eastern woolly lemur travels most often during the first and last hour of the night (Harcourt, 1988). This species travels at an average height in the forest of 5.2 meters (Ganzhorn et al., 1985). The leaps for this species have an average distance of 1.8 meters (Ganzhorn et al., 1985). This species does not use the foot for propulsion when leaping (Demes et al., 1996). During leaping there is a wide range of movements at the hip joint (Demes et al., 1996). When this species descends slowly quadrupedally or downward leaps from trunk to trunk (Walker, 1979). If this species is on the ground it moves by bipedal hopping (Walker, 1979).

SOCIAL BEHAVIOR:
The basic group is composed of a breeding pair and their offspring. The Eastern woolly lemur is most often seen in pairs (Harcourt, 1988). This is a monogamous species. This nocturnal species huddles in groups in vines during the day to sleep (Fleagle, 1988). Members of the pair do not forage or travel together, but do keep in contact during the night with distant communication call (Harcourt, 1991). Ranges of groups do not overlap, and there is much aggression between groups, with a high rate of calling and chasing seen at group home range boundaries (Harcourt and Thornback, 1990).

VOCAL COMMUNICATION:
infant call: This call is composed of plaintive whistlelike noises which are used to attract the attention of the mother by the infant (Petter and Charles-Dominique, 1979).

distant communication call: This call is composed of high-pitched whistles that are modulated and prolonged (Petter and Charles-Dominique, 1979). This call elicits the same call by the receiver (Petter and Charles-Dominique, 1979). This call serves to communicate territorial demarcation (Petter and Charles-Dominique, 1979). Harcourt (1991) reports that this call is used between members of a monogamous pair to keep in contact during the night when traveling and foraging.

alarm call: This call starts out as a faint discreet grunting sound followed by a weak snorting sound when an individual is mildly disturbed, but may be transformed into a cooing call (Petter and Charles-Dominique, 1979). If an individual is highly disturbed the call transforms into a loud trembling call in which the pitch rises in a rapid manner to end on a powerful high-pitched note (Petter and Charles-Dominique, 1979). This sounds like "Ava Hy", hence the name for this species (Petter and Charles-Dominique, 1979).

cohesion call: This is a sudden, high-pitched call that is emitted by an individual when separated from another by a distance of 50 meters following an alarm situation (Petter and Charles-Dominique, 1979).

contact-rejection call: This call is composed of aggressive grunting sounds when an individual is attempting to be grasped and when grasped is transformed into a resonant snorting sound (Petter and Charles-Dominique, 1979).

OLFACTORY COMMUNICATION:
Both sexes have specialized scent glands on the necks used in olfactory communication.

VISUAL COMMUNICATION:

TACTILE COMMUNICATION:

REPRODUCTION:
The avahi gives birth to a single offspring (Fleagle, 1988). Infants are carried by their mothers on the ventral side, or the belly, then later on the infants switch to the dorsal side (the back) of the mother (Ganzhorn et al., 1985). The birth season is from August to September (Harcourt and Thornback, 1990). The gestation period for this species is from 120 to 150 days (Klopfer and Boskoff, 1979).

REFERENCES:
Ankel-Simons, F. 2000. Primate Anatomy. Academic Press: New York.

Burton, F. 1995. The Multimedia Guide to the Non-human Primates. Prentice-Hall Canada Inc.

Demes, B., Jungers, W.L., Fleagle, J.G., Wunderlich, R.E., Richmond, B.G., and Lemelin, P. 1996. Body size and leaping kinematics in Malagasy vertical clingers and leapers. Journal of Human Evolution. Vol. 31, 367-388.

Fleagle, J. G. 1988. Primate Adaptation and Evolution. Academic Press.

Ganzhorn, J.U. 1993. Flexibility and constraints of Lepilemur ecology. In Lemur Social Systems and Their Ecological Basis. eds. P.M. Kappeler and J.U. Ganzhorn. Plenum Press: New York.

Ganzhorn, J.U., Abraham, J.P., and Razananhoera-Rakotomalala, M. 1985. Some aspects of the natural history and food selection of Avahi laniger. Primates. Vol. 26(4), 452-463.

Gingerich, P.D. and Ryan, A.S. 1979. Dental and cranial variation in living Indriidae. Primates. Vol. 20(1), 141-159.

Goodman, S., de Roland, L.A.R., and Thorstrom, R. 1998. Predation on the Eastern woolly lemur (Avahi laniger) and other vertebrates by Henst's goshawk (Accipiter henstii). Lemur News. Vol. 3, 14-15.

Harcourt, C.S. 1987. Ecology and Behaviour of Avahi laniger. (abstract) International Journal of Primatology. Vol. 8, 501.

Harcourt, C.S. 1988. Avahi laniger: A study in inactivity. Primate Eye. Vol. 35, 9.

Harcourt, C. 1991. Diet and behaviour of a nocturnal lemur, Avahi laniger, in the wild. Journal of Zoology. Vol. 223, 667-674.

Harcourt, C. and Thornback, J. 1990. Lemurs of Madagascar and the Comoros. The IUCN Red Data Book. IUCN, Gland, Switzerland and Cambridge, U.K.

Klopfer, P.H. and Boskoff, K.J. 1979. Maternal behavior in prosimians. In The Study of Prosimian Behavior. eds. G.A. Doyle and R.D. Martin. Academic Press: New York.

Petter, J.J. and Charles-Dominique, P. 1979. Vocal communication in prosimians. In The Study of Prosimian Behavior. eds. G.A. Doyle and R.D. Martin. Academic Press: New York.

Tattersall, I. 1982. The Primates of Madagascar. Columbia University Press: New York.

Walker, A. 1979. Prosimian locomotor behavior. In The Study of Prosimian Behavior. eds. G.A. Doyle and R.D. Martin. Academic Press: New York.

Last Updated: March 22, 2007.
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