Hose's Leaf-monkey (Presbytis hosei)

MORPHOLOGY:
Hose's leaf-monkey has a tall sagittal crest that leans forward. This species has a sacculated stomach to assist in the breakdown of cellulose. Hose's leaf-monkey has enlarged salivary glands. The incisors are narrow and the molars have sharp, high crests (Oates and Davies, 1994). This species has a dental formula of 2:1:2:3 on both the upper and lower jaws (Ankel-Simons, 2000). The jaw is deep and the face is short and broad (Oates and Davies, 1994). The pollex (thumb) is reduced in this species (Davies, 1991). The orbits are widely spaced and the hindlimbs are longer as compared to the forelimbs (Oates and Davies, 1994). The pelage of this species is gray on the dorsal side and white on the ventral side (Payne et al., 1985). The hands and feet are blackish in coloration (Payne et al., 1985). The face is pinkish with having a distinct black band across each cheek (Payne et al., 1985). The infants of this species are colored white with black lines down the back and across the shoulders (Payne et al., 1985). The average body mass of an adult male is 6.2 kilograms and for adult females it is 5.57 kilograms (Rowe, 1996).

This species has four subspecies each having different morphological colorations distinct to it:

• Presbytis hosei hosei: This subspecies lacks sexual dichromatism (Groves, 2001). The legs become dark distally with the feet being black (Groves, 2001). The ventral side is buffy-white in coloration (Groves, 2001). On the face, around the eyes is black colored hair, with the rest being pinkish and the lips bluish in color (Groves, 2001). The tail of this subspecies is paler below than above (Groves, 2001).
• Presbytis hosei everetti: This subspecies is sexual dichromatic with the male having black colored hair on the crown and in the female the black color covers the forehead, the nape, and extends laterally to the ear (Groves, 2001).
• Presbytis hosei sabana: The facial skin of this subspecies is reddish with bluish colored lips and black spots on each side of the face between the eyes nose and mouth (Groves, 2001). The crown is gray in coloration (Groves, 2001). The ventral side is gray except for white on the belly and inner side of the limbs (Groves, 2001). The hands and feet are black in coloration (Groves, 2001).
• Presbytis hosei canicrus: The facial skin is blackish down to a line between the mouth and ear where then it becomes whitish buff in coloration (Groves, 2001). The crown is brownish in coloration (Groves, 2001). The ventral side of this subspecies is buffy-white (Groves, 2001).

RANGE:
Hose's leaf-monkey is found on the island of Borneo, in the countries of Indonesia and Malaysia. This species occurs in tall and secondary forests and will occasionally enter plantations (Payne et al., 1985). This species is found in an altitudinal range of 1000-1300 meters (Goodman, 1989).

This species has four subspecies each having different ranges:

• Presbytis hosei hosei: This subspecies may only be found around the lower Baram river (Groves, 2001).
• Presbytis hosei everetti: This subspecies is found along the northwest coast of Sabah into Brunei (Groves, 2001). This subspecies is found from latitude 2 degrees 40' N to Mount Kinabalu (Groves, 2001).
• Presbytis hosei sabana: This subspecies is confined to central and eastern Sabah and southwestern to Kalabakan (Groves, 2001). This subspecies may also be found in far northeastern Kalimantan (Groves, 2001).
• Presbytis hosei canicrus: This subspecies is found on the eastern coast of Borneo from Kutai to Gunung Talisayan (Groves, 2001).

ECOLOGY:
Hose's leaf-monkey is primarily a folivorous species, but will also consume fruits and seeds. The eggs and nestlings have also been found to be consumed, with the gray-throated babbler, Stachyris nigriceps, being on species (Goodman, 1989). Flowers are also eaten by this species (Rowe, 1996). Group sizes tend to range from 6 to 8 individuals (Payne et al., 1985). This species was found to move through the middle levels of the forest canopy (Goodman, 1989). This is an arboreal and diurnal species. Hose's leaf-monkey will occasionally come to the ground to visit natural mineral sources (Payne et al., 1985).

This species is hunted by humans, Homo sapiens, for its gallstones (Rowe, 1996).

LOCOMOTION:
Hose's leaf-monkey moves through the forest quadrupedally (Fleagle, 1988). This species also moves through the forest by leaping (Fleagle, 1988).

SOCIAL BEHAVIOR:
Hose's leaf-monkey has a unimale social system and a polygynous mating system (Payne et al., 1985). Solitary individuals do occur (Bennett and Davies, 1994). Males disperse from their natal groups (Rowe, 1996; Bennett and Davies, 1994). Hose's leaf-monkey has been found to form mixed-species associations with the maroon leaf-monkey, Presbytis rubicunda (Rowe, 1996).

VOCAL COMMUNICATION:
dawn call: This call is given by males at dawn and is a "gurgle growl" like in nature (Rowe, 1996).

alarm call: This call is "grunt-like" (Rowe, 1996).

OLFACTORY COMMUNICATION:

VISUAL COMMUNICATION:

TACTILE COMMUNICATION:
social grooming: This is when one individual grooms another and is used to reinforce the bonds between individuals. Females will perform this behavior on other females more than on males (Rowe, 1996).

REPRODUCTION:
Hose's leaf-monkey gives birth to a single offspring.

REFERENCES:
Ankel-Simons, F. 2000. Primate Anatomy: An Introduction. Academic Press: San Diego.

Bennett, E.L. and Davies, A.G. 1994. The ecology of Asian colobines. in Colobine Monkeys: Their Ecology, Behaviour and Evolution. eds. A.G. Davies and J.F. Oates. Cambridge University Press: Cambridge.

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

Goodman, S.M. 1989. Predation by the grey leaf monkey (Presbytis hosei) on the contents of a bird's nest at Mt. Kinabalu Park, Sabah. Primates. Vol. 30(1), 127-128.

Groves, C.P. 2001. Primate Taxonomy. Smithsonian Institution Press: Washington, D.C.

Oates, J.F. and Davies, A.G. 1994. What are colobines? in Colobine Monkeys: Their Ecology, Behaviour and Evolution. eds. A.G. Davies and J.F. Oates. Cambridge University Press: Cambridge.

Payne, J., Francis, C.M., and Phillipps, K. 1985. A Field Guide to the Mammals of Borneo. Kota Kinabalu and Kuala Lumpur: Sabah Society with World Wildlife Fund Malaysia.

Rowe, N. 1996. The Pictorial Guide to the Living Primates. Pogonias Press: East Hampton, New York.

Last Updated: October 12, 2003.
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