Feeding strategies of primates in temperate and alpine forests: comparison of Asian macaques and colobines.

We analyzed regional variation in the diets of two primate clades, Asian macaques and colobines, whose distributions include temperate-alpine forests. We addressed feeding strategies that enabled them to adapt to harsh environments characterized by relatively low mean temperatures and strong seasonality in both temperature and food availability. Macaques in tropical-lowland forests feed mainly on fruit and animal matter whereas populations in temperate-alpine forests feed more on foliage and on such items as bark and fungi. In comparison, colobines in tropical-lowland forests feed more on fruit and foliage whereas populations in temperate-alpine forests feed less on flowers and more on lichens. Annual precipitation and mean temperature, both of which reflect primary production, had the most significant effects on the feeding behavior of the macaques, whereas only mean temperature had a significant effect on that of colobines. We found two behavioral strategies used by both clades to cope with severe environmental conditions in temperate-alpine forests--shifting to other food items and adjusting feeding plasticity for fruit and foliage. Macaques responded to latitudinal changes by use of both strategies whereas the colobines adapted by using the latter only. By contrast, changes in altitude resulted in the macaques' using the latter strategy and colobines' using both. The different current distributions of Asian macaques and colobines could be attributed to differences in their feeding strategies originating in their digestive systems.