Adult Silvered Leaf Monkey (Trachyphitecus sp. ) can be distinguished by having silver-tip fur, with dark-skinned face, a feature which is entirely different from the infants. Infants can be seen as a starling bright orange. However, in Sabah (Malaysian Borneo) reddish adults also occur. Species Range Species of Silvered Leaf Monkeys can be found ranging from Indochina, Southern Burma, Southern Thailand, Peninsular Malaysia to Sumatra, Java, and Borneo. Group Size Species of Silvered Leaf Monkey are usually found in groups up to about ten.
The average group size of Javan Langur is around seven individuals (V. Nijman, unpubl. data; cited in Nijman and van Balen, 1998). Based on Kool (1991) found that groups ranged in size from 6-21 individuals with one or two adult males in the group. Group sizes were observed to be larger on Lombok Island, Indonesia, in secondary and monsoon forests than in tropical forests (Supriatna et al. , 1986). Foraging Behavior of Silvered Leaf Monkey Silvered Leaf Monkeys are observed feeding on young leaf shoots or forest fruits in swampy areas, riverine forests and back-mangrove (“Silvered Leaf Monkey.
” 2007). The diet of the Leaf Monkey consists of young leaves and leaf buds, including sweet and fleshy fruits (ripe and unripe), flowers, flower buds, and insect larvae (Kool, 1993). During times that fruits are unavailable or not in season, they increase the intake of young shoots/leaves. It was found out that half of the dietary intake for the subspecies T. auratus sondaicus consisted of protein-rich leaves (Kool, 1992, 1993). In addition to that, the leaves that, the Silver Leaf Monkey selects and prefers to eat consists of low-fiber contents which are easily digestible (Kool, 1992).
Silver Leaf Monkey rarely eat mature leaves, they are observed to spent 20% of feeding time foraging on species of Moraceae. When the favored food are scares, their important food source are young leaves of the teak tree (Tectona grandis), (Kool, 1993, 1991). The midrib part of the leaf of teak tree are mostly preferred to be eaten by the Silver leaf Monkey. Nutritional Value of Their Diets Part of their diet, are high protein rich leaves and leaves with low fiber-content which are easily digestible.
According to Kool (1993) twenty seven to thirty seven percent of their diets was fruit in which fifteen to twenty seven percent consists of the diets of unripe fruit, and ten to twelve percent of the diet ripe fruit. These fruits that they consume consists of higher amount of condensed tannins, (which according to Goltenboth 1976; Davies, et al. , 1998; Kool, 1992, is useful in the diet because they may reduce acidosis of the stomach by slowing down the rate of fermentation) and total phenolics. Part of the diet of the subpsecies T.
auratus sondaicus are ripe fruits which was found causing acidosis in colobines, this is maybe the reason why colobines avoid eating this (Goltenboth, 1976; Kool, 1992). Some of the species also prefer eating fruits with seeds. Some of the important species of trees they prefer to consume are from Ficus sinulata, Ficis sumatrana and Vitex pinnata (Kool, 1993). Depending on what kind of fruits was in season especially during the month of July, August, September, January and February, the kind of food that different groups prefers, varies.
Groups may feeds simultaneously having the same food preference. Individuals may be observed eating while the others are traveling or resting. It was also observed that compared to other group of adults and sub-adults the male Silvered Leaf Monkey fed less frequently (Brotoisworo and Dirgavusa, 1991). Locomotion It was observed that the silvered leaf monkey (Javan langur) moves through the forest, quadrupedally (Rowe, 1996). Social Behavior The species of Javan langur are found living in social groups of one or two adult males and some groups on Lombok islands are observed to have only one male.
The males were observed to separate and travel solitarily or mixed with all-male groups. The male tends to maintain close proximity with other males the same is true with the females, who tend to maintain close proximity with other females. Aggressive behavior of adult females against one another of the same sex can be observed. Some females may tend to care infants which are not from them (Kool, 1991; Supriatna, etal. 1986; Bennett and Davies, 1994; Rowe, 1994; and Mengantara and Dirgayusa, 1994). Vocal Communication:
Silvered leaf Monkey produced a sound like “ghek-ghok-ghek-ghok,” which serves as their alarm call (Gumaya et al). Reproduction: The species of silvered leaf monkey produces or gives birth to only one offspring at a time.
References 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. Brotoisworo, E. and Dirgayusa, I. W. A. 1991. Ranging and Feeding Behavior of Presbytis cristata in the Pangandaran Nature Reserve, West Java, Indonesia.
in Primatology Today. eds. A. Ehara, T. Kimura, O. Takenaka, and M. Iwamoto. Elsevier Science Publishers: Amsterdam. Davies, A. G. , Bennett, E. L. , and Waterman, P. G. 1988. Food Selection By Two South-east Asian colobine monkeys (Presbytis rubicunda and Presbytis melalophos) in Relation to Plant Chemistry. Biological Journal of the Linnean Society. Vol. 34, 33-56. Djuwantoko. 1994. Habitat and Conservation of Ebony Leaf Monkey in Deciduous Forests (teak), in Central Java. (abstract) XVth Congress of the International Primatological Society.
Bali-Indonesia. Goltenboth, R. 1976. Non Human Primates (apes, monkeys and prosimians). in The Handbook of Zoo Medicine. (translation) eds. H-G. Klos and E. M. Lang. Van Nostrand Reinhold: New York. Gurmaya, K. J. , Adiputra, I. M. W. , Saryatiman, A. B. , Danardono, S. N. , and Sibuea, T. T. H. 1994. A Preliminary Study on Ecology and Conservation of the Java Primates Kool, K. M. 1991. “Behavioral Ecology of the Silver Leaf Monkey, Trachypithecus auratus sondaicus, in the Pangandaran Nature Reserve,” West Java, Indonesia: (abstract) Primate Eye.
Vol. 44, 19-20. Kool, K. M. 1992. Food Selection by the Silver Leaf Monkey, Trachypithecus auratus sondaicus, in Relation to Plant Chemistry. Oecologia. Vol. 90, 527-533. Kool, K. M. 1993. “The Diet and Feeding Behavior of the Slilver Leaf Monkey, (Trachypithecus auratus sondaicus) in Indonesia. ” International Journal of Primatology: Vol. 14(5), 667-700. Mengantara, E. and Dirgayusa, I. W. A. 1994. Social Behavior of lutung (Trachypithecus auratus sondaicus) in Pangandaran Nature Reserve. (abstract) XVth Congress of t