The average body mass for an adult male grizzled leaf-monkey is around 6.5 kilograms, and for the female it is around 6.7 kilograms (Fleagle, 1988). This species has a sacculated stomach to assist in the breakdown of cellulose. The grizzled leaf-monkey has enlarged salivary glands. This species has a sacculated stomach to assist in the breakdown of cellulose. 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 grizzled leaf-monkey has two subspecies each having their own pelage coloration:
Presbytis comata comata: On the dorsum the pelage is a dark gray color (Nijman, 1997a). The tail on this subspecies is dark gray to black and the arms and legs are dark gray, being darker than the back (Nijman, 1997a). The innerside of the arms, legs, and tail are whitish (Nijman, 1997a). On the head there is a black colored prominent crest (Nijman, 1997a). The neonate has a pelage coloration that varies from medium gray to dark gray (Nijman, 1997a).
Presbytis comata fredericae: The dorsum (dorsal side) is black and the throat, upper chest are white or light gray (Nijman, 1997a; Brandon-Jones, 1995). The lower abdomen, innerside of legs, arms and tail are white (Nijman, 1997a). On the thumbs and middle and sometimes the distal phalanges of the digits there is a small amount of white (Brandon-Jones, 1995). The neonate has a pelage coloration that varies from dark gray to black (Nijman, 1997a).
The grizzled leaf-monkey is found in the country of Indonesia on the island of Java. On Java this species is found from the westernmost tip at Ujung Kulon to Mt. Lawu on the border between central and east Java (Nijman, 1997b; Nijman and van Balen, 1998). This species lives in primary and secondary lowland rainforests (Gurmaya et al., 1994). The grizzled leaf-monkey can be found in altitudes up to 2000 meters (Van der Zon, 1979; cited in Gurmaya et al., 1994), although Nijman (1997b) found that the altitudinal range is 2500 meters. Nijman (1997a) found this species to occur in primary and secondary forests, ecotones, in the forest interior, lowland forests, in forests on steep slopes and hills, and in montane and upper montane forests. The grizzled leaf-monkey has also been found on plantations and orchards (Sujatnika, 1992; cited in Nijman, 1997b; Melisch and Dirgayusa, 1996; Seitre and Seitre, 1990). At Gunung Pongkor, Mt. Halimun National Park this species was found to occur in hill forests from 500 to 1000 meters in altitude (Indrawan et al., 1995/1996).
The two different subspecies have different ranges:
Presbytis comata comata: This subspecies is found in west Java (Nijman, 1997a).
Presbytis comata fredericae: This subspecies is found in central Java (Nijman, 1997a). This subspecies is only known from Mt. Slamet, the northwestern slopes of the mountains north of the Dieng plateau, and Mt. Lawu (Nijman and Sozer, 1995). In the Dieng Mountains, this subspecies is found to live in primary and secondary forests, at the edges and the interior, and in lowland forests, forests on steep slopes and hills, and upper montane forests (Nijman and van Balen, 1998). In the Dieng Mountains this subspecies has been observed at an altitude of 2565 meters (Nijman and Sozer, 1995).
The grizzled leaf-monkey is primarily a folivorous species, but will also consume fruits, flowers, and seeds. Ruhiyat (1983) found that the diet of this species consisted of 59.1% young leaves, 13.5% fruits, 7.0% flowers, 5.6% mature leaves, 4.1% fungi, 2.7% pseudobulbs, 1.5% branch tips, and 0.7% seeds. The leaves taken generally are immature ones that have a low level of lignins and tannins (Gurmaya et al., 1994). Preferred leaves of this species include: Ficus pubinervis, Passiflora ligularis, Elaegnus triflora, Schefflera aromatica, Jasminum azoricum, Hoya sp., and Aeshynanthus sp. (Ruhiyat, 1983). This species prefers leaves of epiphytes and lianas in the lower and middle layers of the forest (Ruhiyat, 1983). Preferred fruits of this species are: Premna parasitica, Pygeum spp., Saurauia spp., and Castanopsis argentea (Ruhiyat, 1983). During the fruiting season this species was found to be attracted to orchards and other solitary fruiting trees (Melisch and Dirgayusa, 1996). Flowers of the species Pandanus furcatus and petioles of Alsophylla glauca are preferred food items of the grizzled leaf-monkey (Ruhiyat, 1983). This species rarely drinks water; it receives most of its water from the food it eats. The grizzled leaf-monkey has been observed to come to the ground and eat a reddish colored soil (Ruhiyat, 1983). There are three to four feeding peaks during the day for an individual (Ruhiyat, 1983).
Group sizes for this species range from 3 to 20 individuals. Nijman (1997b) found that on Mt. Slamet, central Java, that group sizes ranged from 4 to 10 individuals. At Gunung Tukung Gede Nature Reserve, the size of groups ranged from 5 to 23 individuals (Melisch and Dirgayusa, 1996). At Mt. Prahu, central Java, group sizes for this species ranged from 2 to 13 individuals (Nijman and van Balen, 1998). This species is found at an average height of 25 meters in the forest, in the upper canopy of the forest (Melisch and Dirgayusa, 1996). The day range of a group will decrease with increasing rainfall (Ruhiyat, 1983). When feeding, traveling and resting, group kept close together (Ruhiyat, 1983). Usually the adult male will be positioned at the front or rear of the group when feeding, traveling, or resting, except when sleeping at night when the adult male is positioned in the middle of the group (Ruhiyat, 1983). Groups will sometimes split for temporary periods of time (Ruhiyat, 1983). When coming together after splitting-up, group members will emit the kik call when rejoining (Ruhiyat, 1983). During daily activity, resting (60%) made up of most of the time, with feeding occurring 30% of the time and traveling only 5% of the time of an individual (Ruhiyat, 1983). This is a diurnal and an arboreal species. This species will rarely use the same sleeping site more than once, and sleeping sites tend to be located on ridges or higher places (Ruhiyat, 1983). Most members of the group sleeps in the upper layer of the canopy at about 20 meters, sometimes up to 40 meters, but the adult male mostly sleeps in the middle layer at a height of 10-20 meters (Ruhiyat, 1983).
Predators of the grizzled leaf-monkey could be the leopard, Panthera pardus, and the fishing cat, Prionailurus viverrinus (Melisch and Dirgayusa, 1996; Seidensticker, 1983; Ruhiyat, 1983). When pursued by humans, Homo sapiens, this species would drop to the forest floor and flee through the dense understory (Brandon-Jones, 1995).
The grizzled leaf-monkey moves through the forest quadrupedally (Fleagle, 1988). This species also moves through the forest primarily by leaping and also to a lesser extent by forelimb suspension (brachiation) (Fleagle, 1988).
The grizzled leaf-monkey has a unimale social system and a polygynous mating system. More than one male has been observed in a group even though usually there is only one (Ruhiyat, 1983). This is a territorial species that has aggressive encounters with conspecific groups. A group's home range will overlap with the home range of other groups, and intergroup aggression will occur in overlap zones if preferred foods of the grizzled leaf-monkey are present in abundance (Ruhiyat, 1983). The adult male is dominant over all other members of the group (Ruhiyat, 1983). Females perform most of the grooming bouts in the group. Males disperse from the natal group before adolescence. This species has been found to form mixed-groups with the ebony leaf-monkey, Trachypithecus auratus (Nijman, 1997b).
Social play occurs in this species with most bouts occurring amongst juvenile and infant males (Ruhiyat, 1983). Juvenile females and adult females rarely engage in social play (Ruhiyat, 1983).
VOCAL COMMUNICATION: kik: This call is a fast sequence of 20 "kik" notes heard within 2.5 seconds (Ruhiyat, 1983). This call is given by adult males during intergroup encounters (Ruhiyat, 1983). This call is also given to humans and when large trees fell down (Ruhiyat, 1983). An adult female would emit this call when she missed her infant, but the call is weaker and shorter (Ruhiyat, 1983). When the adult male utters this call, other group members move to the upper levels of the canopy (Ruhiyat, 1983).
hiccup: This call serves as a soft warning and is heard when an enemy is far away (Ruhiyat, 1983). This call is emitted by the adult male of a group (Ruhiyat, 1983).
ngek: This is a nasal weak call heard when foraging (Ruhiyat, 1983).
nguok: This call is emitted by both adult males and females when two groups would approach and confront each other (Ruhiyat, 1983).
chiet: This call is given by adult females after adult males perform the kik display (Ruhiyat, 1983). This call is also heard by embracing females after two subgroups come together (Ruhiyat, 1983).
chiit: This is a squeak type call that is emitted by infants when they are separated from their mothers or when they are being transferred (Ruhiyat, 1983).
ngiik: This call is emitted by adult females and juveniles (Ruhiyat, 1983). This is heard when individuals grimace when they presented and were chased by more dominant individuals (Ruhiyat, 1983). This call serves to communicate submission (Ruhiyat, 1983).
VISUAL COMMUNICATION: kik display: This behavior is performed by an adult male of a group when he locates another conspecific group (Ruhiyat, 1983). This is where an adult male will emit a series of kik calls while running along a branch horizontally and/or leaping vertically about 5 to 15 meters (Ruhiyat, 1983). This behavior is responded to with a reciprocal display by adult males of the other group (Ruhiyat, 1983). Other members of the group will emit chiet calls during or after the male performs this display (Ruhiyat, 1983).
rush: This is where the adult male of one group will rush towards the adult female and/or juveniles of another group (Ruhiyat, 1983). This is responded to running away by the individuals being rushed (Ruhiyat, 1983). The adult male of the other group counter-attacks the male performing this behavior (Ruhiyat, 1983).
TACTILE COMMUNICATION: social grooming: This is when one individual grooms another and is used to reinforce the bonds between individuals.
The grizzled leaf-monkey gives birth to a single offspring. Ruhiyat (1983) found no definite birth season for this species. The mother holds the infant ventrally until it is about one year old (Ruhiyat, 1983). Infant transferring has been observed where the adult female hands her infant over to other adult female or juvenile females (Ruhiyat, 1983). After about 1.5 years of age the young will stop following its mother (Ruhiyat, 1983).
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