Demography of Agile Gibbons (Hylobates agilis) in a Lowland Tropical Rain Forest of Southern Sumatra, Indonesia: Problems in Paradise
- 432 Downloads
Gibbons are among the best-studied Asian primates, but few studies address their demography and life history strategies. We used annual censuses to study the demography of agile gibbons (Hylobates agilis) between 1998 and 2009 in rain forests of Bukit Barisan Selatan National Park, Indonesia. The population declined from 22 individuals (9 groups) to 14 individuals (5 groups) over the 12 yr of study. Infant survival to the juvenile age class was 33.3%, and 16.7% of infants survived to the subadult age class. The interbirth interval was 3.83 ± 1.15 yr and birth rate was 0.22–0.28 infants female–1 yr–1. Two groups colonized the study area but subsequently disappeared. We documented 7 immigrations, 17 disappearances, and ≥10 transients in the population. Compared to lar gibbons (Hylobates lar) and Bornean white-bearded gibbons (Hylobates albibarbis), Way Canguk’s agile gibbon population is characterized by slow reproduction, low survival, and high group turnover. We hypothesize that, although the habitat is high in fruit resources, agile gibbons may be displaced or excluded from the best fruit resources by larger and more numerous competitors, incurring costs of decreased opportunities to forage and increased travel, and leading to higher mortality for young agile gibbons. The reproductive potential of this agile gibbon population is insufficient to compensate for high mortality, and the population is unlikely to persist without immigration from outside the area. Given the agile gibbons’ endangered status and limited capacity to respond demographically to change, it is likely that intensive management interventions will be required to conserve this species.
KeywordsAgile gibbon Demography of agile gibbons Resource competition Sumatra, Indonesia
This research is a collaborative effort by the Wildlife Conservation Society and the Indonesian Ministry of Forestry, Directorate General for Nature Conservation (PHKA). Our research was funded by the Wildlife Conservation Society, the U.S. Fish and Wildlife Service Great Apes Conservation Fund (grant no. 98210-1-G084), the Disney Conservation Fund, and E. McBean. We thank A. Dwiyahreni, M. Iqbal, A. Nurcahyo, M. Nusawalo, M. Prasetyaningrum, M. Rusmanto, Sunarto, D. Suyadi, N. Winarni, Aris, Bawk, Tegu, and Wariono for assistance with data collection over the years. A. Elder provided valuable insights into the interspecific relationships of Way Canguk primates, L. Morino provided details of clouded leopard predation on a juvenile siamang at Way Canguk, and R Palombit and C. van Schaik provided information on the relationships of lar gibbons and siamangs in northern Sumatra. Our manuscript was greatly improved by the comments of J. Setchell and 2 anonymous reviewers.
- Altmann, J. (1980). Baboon mothers and infants. Cambridge: Harvard University Press.Google Scholar
- Bartlett, T. Q. (2007). The hylobatidae small apes of Asia. In C. J. Campbell, A. Fuentes, K. C. MacKinnon, M. Panger, & S. K. Bearder (Eds.), Primates in perspective (pp. 274–289). Oxford: Oxford University Press.Google Scholar
- Borries, C., Savini, T., & Koenig, A. (2010). Social monogamy and the threat of infanticide in larger mammals. Behavioral Ecology and Sociobiology. doi: 10.1007/s00265-010-1070-5.
- Chivers, D. J. (1974). The siamang in Malaya: a field study of a primate in a tropical rain forest. In H. Kuhn, W. P. Luckett, C. R. Noback, A. H. Schultz, D. Starck, & F. S. Szalay (Eds.), Contributions to primatology (Vol. 4, pp. 1–335). Basel: S. Karger.Google Scholar
- Chivers, D. J., & Raemaekers, J. J. (1980). Long-term changes in behavior. In D. Chivers (Ed.), Malayan Forest primates: Ten years’ study in tropical rain forest (pp. 209–258). New York: Plenum Press.Google Scholar
- Collias, N., & Southwick, C. (1952). A field study of population density and social organization in howling monkeys. Proceedings of the American Philosophical Society, 96, 143–156.Google Scholar
- Elder, A. A. (2010). Sleeping strategies of three sympatric primate species at Way Canguk, Sumatra. In American Society of Primatology Conference (Abstract) Elder abstract #113, Location Louisville, KY on 16–19 June 2010. http://www.asp.org/asp2010/abstractDisplay.cfm?abstractID=2840&confEventID=3079
- Geissmann, T. (1991). Reassessment of age of sexual maturity in gibbons (Hylobates ssp.). American Journal of Primatology, 23, 11–22.Google Scholar
- Geissman, T. (2007). Status reassessment of the gibbons: results of the Asian primate Red List workshop 2006. Gibbon Journal, 1, 5–15.Google Scholar
- IUCN (2010). IUCN Red list of threatened species. Version 2010.3. Retrieved from www.iucnredlist.org.
- Janson, C. H., & van Schaik, C. P. (1993). Ecological risk aversion in juvenile primates: slow and steady wins the race. In M. E. Pereira & L. A. Fairbanks (Eds.), Juvenile primates: Life history, development and behavior (pp. 57–74). Oxford: Oxford University Press.Google Scholar
- Kinnaird, M. F., & O’Brien, T. G. (1998). Ecological effects of wildfire on lowland rainforest in Sumatra. Conservation Biology, 12, 954–956.Google Scholar
- Lappan, S. (2005). Biparental care and male reproductive strategies in siamangs (Symphalangus syndactylus) in southern Sumatra. Ph.D. thesis, New York University.Google Scholar
- Leighton, D. (1987). Gibbons: territoriality and monogamy. In B. Smuts, D. Cheney, R. Seyfarth, R. Wrangham, & T. Struhsaker (Eds.), Primate societies (pp. 135–145). Chicago: University of Chicago Press.Google Scholar
- Marshall, A. J. (2004). The population ecology of gibbons and leaf monkeys across a gradient of Bornean forest types. Ph.D. thesis, Harvard University.Google Scholar
- Marshall, A. J., & Leighton, M. (2006). How does food availability limit the population density of agile gibbons? In G. Hohmann, M. Robbins, & C. Boesch (Eds.), Feeding ecology of the apes (pp. 313–335). Cambridge: Cambridge University Press.Google Scholar
- Marshall, A. J., Cannon, C. H., & Leighton, M. (2009). Competition and niche overlap between gibbons (Hylobates albibarbis) and other frugivorous vertebrates in Gunung Palung National Park, West Kalimantan, Indonesia. In S. Lappan & D. Whittaker (Eds.), The Gibbons: New Perspectives on Small Ape Socioecology and Population Biology (pp. 161–188). Developments in Primatology: Progress and Prospects. New York: Springer.Google Scholar
- Palombit, R. A. (1992). Pair bonds and monogamy in wild siamang (Hylobates syndactylus) and white-handed gibbon (Hylobates lar) in Northern Sumatra. Ph.D. thesis, University of California, Davis.Google Scholar
- Pulliam, H. R. (1988). Sources, sinks and population regulation. American Naturalist, 132, 652–661.Google Scholar
- Pulliam, H. R. (1996). Sources and sinks: Empirical evidence and population consequences. In O. E. J. Rhodes, R. K. Chesser, & M. H. Smith (Eds.), Population dynamics in ecological space and time (pp. 45–69). Chicago: University of Chicago Press.Google Scholar
- Rabinowitz, A. (1989). The density and behavior of large cats in a dry tropical forest mosaic in Huai Kha Khaeng Wildlife Sanctuary, Thailand. Natural History Bulletin of the Siam Society, 37, 235–251.Google Scholar
- Raemaekers, J. J., & Chivers, D. J. (1980). Socio-ecology of Malayan forest primates. In D. J. Chivers (Ed.), Malayan Forest primates: Ten years’ study in tropical rain forest (pp. 279–316). New York: Plenum Press.Google Scholar
- Reichard, U. H. (2003). Social monogamy in gibbons: The male perspective. In U. H. Reichard & C. Boesch (Eds.), Monogamy: Mating strategies and partnerships in birds, humans and other mammals (pp. 3–25). Cambridge: Cambridge University Press.Google Scholar
- Sokal, R. R., & Rolf, F. J. (1995). Biometry (3rd ed.). New York: Freeman.Google Scholar
- Whittaker, D. J., & Lappan, S. (2009). The diversity of small apes and the importance of population-level studies. In S. Lappan & D. J. Whittaker (Eds.), The Gibbons: New Perspectives on Small Ape Socioecology and Population Biology (pp. 3–10). Development in Primatology: Progress and Prospects. New York: Springer.Google Scholar
- Yanuar, A. (2009). The population distribution and abundance of siamangs (Symphalangus syndactylus) and Agile gobbons (Hylobates agilis) in West Central Sumatra, Indonesia. In S. Lappan & D. J. Whittaker (Eds), The Gibbons: New Perspectives on Small Ape Socioecology and Population Biology (pp. 453–465). Development in Primatology: Progress and Prospects. New York: Springer.Google Scholar
- Yanuar, A., & Sugardjito, J. (1993). Population survey of primates in Way Kambas National Park, Sumatra, Indonesia. Tigerpaper, 20, 30–36.Google Scholar