Paleobiologists have long had a keen interest in the diets of prehistoric creatures, because `diet` is the key to so many important questions in evolution. Of the techniques currently available for making dietary inferences, three (analyses of tooth shape, dental microstructure, and microscopic wear patterns on teeth) stand ready to yield new insights, if only better data from living animals with known diets can be gathered. The purpose of this study is to push each of these techniques closer to their paleobiological potential through a study of living primates with known diets. The animals to be studied will be from 35 social groups of howling monkeys, Alouatta palliata, living in patches of dry tropical forest at Hda. La Pacifica near Canas, Costa Rica. The howlers at La Pacifica have been the subject of behavioral observation for over 25 years. Thus their diet is known to vary from season to season, and between microhabitats at La Pacifica. It also includes a mixture of fruit and vegetation making it a good model of the diet of medium to large-sized fossil primates. Animals will be periodically captured and released, and while captured, high resolution copies of their teeth will be made. Scanning electron microscopy and 3-D digitizing of the dental replicas will yield new measurements of tooth microstructure, tooth shape, and tooth wear. In conjunction with analyses of food samples, stomach contents, fecal samples, and dust collected from the forest canopy, this study will document, once and for all, the functional implications of tooth wear in these animals. This work should lead to new insights into (1) changes in tooth use associated with both growth and development and changes in diet, (2) variations in dental microstructure, (3) causes of tooth wear, and (4) physical properties and phytolith content of Neotropical plants.
