Western Woolly Lemur (Avahi occidentalis)

Ma les of this species have an average body mass of 814 grams and females have an average body mass of 777 grams (Fleagle, 1998). 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 which is light to medium gray dorsally and light colored ventrally (Tattersall, 1982). The tail is colored gray with reddish elements (Tattersall, 1982). The face, throat, and cheeks are also light colored like the ventral side (Tattersall, 1982).

This species is found on the island of Madagascar, and lives in the dry deciduous forest. This species is found to the north and east of the Betsiboka River and from the Ankarafantsika Reserve to the Bay of Narinda (Harcourt and Thornback, 1990). In the forest this species is most often found in the canopy (Warren, 1997).

The Western woolly lemur is found in the following reserves in Madagascar (Harcourt and Thornback, 1990):

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). 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 Western 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). Where the Western 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 avahi is a vertical leaper. The Western woolly lemur travels most often during the first and last hour of the night (Harcourt, 1988). During the night this species covers large distances when traveling (Warren and Crompton, 1997). This species travels at an average height in the forest of 5.2 meters (Ganzhorn et al., 1985). The leaps for this species have a mean length of 1.51 meters (Warren, 1997). When leaping this species has a preference to take-off from horizontal supports (Warren, 1997). 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).

The basic group is composed of a breeding pair and their offspring. This species is found mostly commonly in groups of three (Harcourt and Thornback, 1990). This is a monogamous species. This nocturnal species huddles in groups in vines during the day to sleep (Fleagle, 1988). Ranges of groups do overlap considerably which differs from Avahi laniger in which group ranges do not overlap (Harcourt and Thornback, 1990).

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).

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).

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



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).

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.

Fleagle, J. G. 1998. Primate Adaptation and Evolution. Academic Press: New York.

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.

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

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.

Warren, R.D. 1997. Habitat use and support preference of two free-ranging salutatory lemurs (Lepilemur edwardsi and Avahi occidentalis). Journal of Zoology. Vol. 241, 325-341.

Warren, R.D. and Crompton, R.H. 1997. Anomalous salutatory locomotor adaptation in two small-bodied, folivorous, nocturnal lemurs. Primate Eye. Vol. 63, 18.

Last Updated: March 22, 2007.
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