This chapter will focus on the relationships among physiology, behavior, and ecology in the Asian colobine monkeys. Colobines are known for their specialized digestive physiology, including, especially, their unique sacculated stomach containing anaerobic cellulytic bacteria (Bauchop and Martucci, 1968). This physiological specialization allows them to extract nutrients from foliage more efficiently, but digestive efficiency via microbial fermentation has a cost: a slower rate of digestion. This, combined with a small size (when compared to other animals utilizing microbial symbionts), limits colobines' gross intake of food, and forces them to balance the quality and the quantity of food ingested. The costs and benefits of the colobine digestive system have a profound impact on social structure and ecology, underlying social relationships, home range size, population density, activity patterns, and intergroup interactions as well as diet. For example, the ability to digest low quality food may widen the resource base, directly affecting home range size and intergroup interactions.
In the following review, we emphasize detailed, longer-term studies, many of them only recently completed, which in many cases have clarified our perceptions of this group. The tables summarize information from this literature. We follow the taxonomic classifications of Oates, Davies and Delson (1994) with one exception; we retain the separation of Rhinopithecus and Pygathrix (Jablonski and Peng, 1993; Jablonski, 1995), thus recognizing seven genera.
Asian colobines are typically organized into one-male social groups (one male, several females, and offspring).