Maroon Leaf-monkey (Presbytis rubicunda)

This species has a sacculated stomach to assist in the breakdown of cellulose. In the forestomach there are microbes that break down cellulose into fatty acids by anaerobic fermentation (Davies et al., 1988). The microbes in the forestomach also detoxify alkaloid defense chemicals in plants (Davies et al., 1988). The maroon leaf-monkey has enlarged salivary glands. This species has a dental formula of 2:1:2:3 on both the upper and lower jaws (Ankel-Simons, 2000). The incisors are narrow and the molars have sharp, high crests (Oates and Davies, 1994). 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 average body mass for adult males is 6.290 kilograms and for adult females it is 6.170 kilograms (Fleagle, 1999). The pelage color ranges from red to reddish-orange with the stomach region being a lighter shade and the hands and tip of the tail being darker shades.

This species has five subspecies (Napier and Napier, 1967):
  • Presbytis rubicunda rubicunda
  • Presbytis rubicunda rubidus
  • Presbytis rubicunda ignitus
  • Presbytis rubicunda carimatae
  • Presbytis rubicunda chryseus
Maroon Leaf-monkey

The maroon leaf-monkey is found on the island of Borneo, in the countries of Indonesia and Malaysia. The subspecies Presbytis rubicunda carimatae is found on the island of Karimata, west Kalimantan, Indonesia (Yanuar et al., 1993). This species lives in primary and secondary lowland forests, not above 2000 meters. The maroon leaf-monkey also lives in swamp forests (Chivers and Burton, 1988). This species can also tolerate forests that have been redeveloped after logging has taken place. In Kalimantan Tengah this species is found in the Tanjung Puting Nature Reserve and Pleihari Martapura Nature Reserve (Chivers and Burton, 1988). In Sepilok, Sabah, northern Borneo, this species is found in evergreen forests (Bennett and Davies, 1994). On Karimata Island the subspecies Presbytis rubicunda carimatae preferred to live in swamp forests and would occasionally visit native gardens in search of food (Yanuar et al., 1993).

The maroon leaf-monkey is a folivorous species, but it could also be considered a gramnivorous species because in certain months of the year it relies more heavily upon seeds. Seeds may be heavily consumed by this species because of the sensitivity of their forestomach microbes to changes in pH levels, a slow food passage rate, and the susceptibility of the forestomach microbes to bacteriocides (Davies, 1986). Pulpy, ripe, succulent fruits are avoided by this species because they have high levels of organic acids that could disrupt forestomach pH and can acidosis (Davies et al., 1988). This species prefers leaves that are immature to those which are more mature. Fruits with large seeds and little flesh, flowers, and pith are also eaten. The maroon leaf-monkey also consumes termite clay for mineral nutrients (Davies and Baillie, 1988). Fruits located at the tip of a branch are foraged by bending the branch until it reaches the mouth, with small fruits taken by the mouth and larger fruits taken by the hands (Suprianta et al., 1986). Flowers of the genus Fragraea are eaten whole, but flowers of the genus Deplanchea have only the petals consumed (Suprianta et al., 1986). The subspecies Presbytis rubicunda carimatae was found to consume more leaves than other subspecies (Yanuar et al., 1993).

At Tanjung Puting, Indonesia, the diet of this species consisted of 52% fruits (including seeds), 36% leaves, and 12% flowers (Suprianta et al., 1986). Leaves consumed included: Baccaurea sumatrana, Ficus sp., Lithocarpus cycloporus, and Rourea mimosoides (Suprianta et al., 1986). Fruits consumed by the maroon leaf-monkey included: Strychnos ignathii, Mezzetia leptopoda, Cantleya corniculata, Zizyphus callophyla, Palaquium quercifolium, Pithecellobium ellipticum, Rourea minor, and Garcinia sp. (Suprianta et al., 1986). Flowers eaten include Deplanchea bancana, Dillenia sp., and Fragraea sp. (Suprianta et al., 1986).

In Sabah, northern Borneo, the diet of the maroon leaf-monkey was found to consist of 36.6% young leaf parts, 30.1% seeds, 19.2% whole fruits, and 11.1% flowers (Davies and Baillie, 1988). Food came from both trees and lianas (Davies and Baillie, 1988). From June to September the diet of this species was composed of 68 to 90 percent large, dry seeds (Davies and Baillie, 1988; Davies, 1991). This species was found to consume seeds and/or leaves from six dipterocarp species, with the seeds of Shorea xanthophylla being an example (Davies et al., 1988). Seeds tended to have relatively high levels of tannins and fibre (Davies et al., 1988). Tannins might be important because they can aid in protein digestibility by shielded them from forestomach microbes that would otherwise degrade them (Davies et al., 1988). Seeds were taken from fruits with juicy, fibrous flesh, examples being Xerospermum intermedium and Wallucharia wallichii (Davies, 1991). Small seeds were consumed from the species Anthocephalus chinensis and Carallia borneensis (Davies, 1991). Young leaves had their greatest consumption in the month of June (Davies and Baillie, 1988; Davies, 1991). Fruits consumed tended to be unripe and dry (Davies et al., 1988). Fruits also tend to have dull green or brown pericarps and pericarps that are thick (Davies, 1991). Flowers were mostly consumed between March and May, the peak flowering season except for on species that was eaten in December (Davies and Baillie, 1988). Mature leaves were only consumed by the maroon leaf-monkey during the rainy season when other food sources were scarce (Davies and Baillie, 1988). Petioles of the species Omphalia bracteata were eaten on mature leaves (Davies, 1991). Feeding on bamboo pith was also observed in Sabah (Davies et al., 1988; Davies, 1991). This species was found to exploit more relatively rare species of trees for food (Davies et al., 1988). Young leaves had higher levels of protein compared with seeds and whole fruits (Davies, 1991). Food from lianes accounted for a high percentage of the diet (32%) (Davies, 1991; cited in Bennett and Davies, 1994). Feeding on soil from a termite mound was observed in this species (Davies and Baillie, 1988). The termite mound was made by a member of the genus Macrotermes (Davies and Baillie, 1988). Individuals would tear off the top layer of soil and consume the freshly exposed soil (Davies and Baillie, 1988). Termite mounds may be preferred over surrounding soil because they have a higher concentration of organic matter and nutrients such as calcium, magnesium, potassium, and phosphorus (Davies and Baillie, 1988). Consuming termite soil may help to relieve acidosis of the forestomach as well as supplementing the diet with scarce nutrients (Davies and Baillie, 1988). Termite soil may also assist in the deactivation or absorption of toxins that serve as protection for plants (Davies and Baillie, 1988).

Group sizes range from 2 to 13 individuals (Davies, 1984; Supriatna et al., 1986; Davies and Baillie, 1988). In Kalimantan Tengah group sizes for this species ranged from 1 to 8 individuals (Chivers and Burton, 1988). The maroon leaf-monkey is a diurnal and an arboreal species. Groups will split into subgroups after the first foraging bout in the morning (Suprianta et al., 1986; Davies, 1987). The group will re-unite in the late afternoon (Suprianta et al., 1986). After a series of feeding bouts in the morning the group will take a long rest at mid-day (Suprianta et al., 1986). When the group is alarmed an individual will sound an alarm call then the adult male will move the group away from the area, but only for a short distance before the group will freeze (Suprianta et al., 1986). Groups have home ranges that overlap, but each group has a core area where the sleeping site is located (Suprianta et al., 1986). The size of a group's home range is correlated with group size where smaller groups have smaller home ranges (Suprianta et al., 1986).

The maroon leaf-monkey moves through the forest quadrupedally (Fleagle, 1988).

The maroon leaf-monkey has a unimale social system and a polygynous mating system (Suprianta et al., 1986; Davies, 1987). Groups are composed of one adult male, one or more adult females, subadults, juveniles, and infants (Suprianta et al., 1986). The maroon leaf-monkey may only have one male per group due to a reduced predation risk (van Schaik and Horstermann, 1994). Males emigrate from their natal group shortly before adolescence. Some females also disperse from their natal group (Suprianta et al., 1986). Males also can travel solitarily or in all-male groups before they find a unimale group. Solitary males may challenge a resident group male for control of the group and sometimes may take subadult and/or juvenile females with him to form a new group (Davies, 1987). Adult females may stay with the resident male for fear of infanticide by the challenging male (Davies, 1987). There are no dominance hierarchies amongst females in terms of access to food resources (Yeager and Kirkpatrick, 1998). The maroon leaf-monkey is a territorial species that will chase other groups out of the home range (Davies, 1984, 1987; cited in Stanford, 1990). This species was found to form asscoiations with Presbytis hosei (Rowe, 1996).

loud call: This is emitted by males and is used to demarcate the group's territory.

alarm call: This call is given upon sighting an intruder (Suprianta et al., 1986). The adult male of a group will give this while the rest of the group is fleeing (Suprianta et al., 1986).



social grooming: This is when one individual grooms another and is used to reinforce the bonds between individuals.

The maroon leaf-monkey gives birth to a single offspring.

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Last Updated: June 21, 2007.
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