WRIGHT, B.W.*; STEVENS, N.J.; ULIBARRI, L.; O’BRIEN, J.; COVERT, H.H.; NADLER, T.; George Washington Univ., USA; Ohio University, USA; Univ. of Colorado, Boulder, USA; Univ. of Colorado, Boulder, USA; Univ. of Colorado, Boulder, USA; Endangered Primate Rescue Center, Cuc Phuong Nat. Park, Vietnam: Relationships between leaf toughness and food processing behavior among four Vietnam leaf monkeys

This study identifies relationships between the toughness of ingested leaves and patterns of food processing behavior among four captive colobine primates (Pygathrix nemaeus, P. cinerea, Trachypithecus delacouri, and T. laotum hatinhensis) at the Endangered Primate Rescue Center, Cuc Phuong National Park, Vietnam. The majority of leaves presented to these species are found in their natural habitat. By providing the primates with monospecific bundles of leaves we were able to rank the most preferred, moderately preferred, and least preferred foods. Toughness was measured with a portable tester designed by Lucas et al. (2001). Chewing rates, durations of chewing bouts, and the number of chews per bout were calculated from video. Preferred leaves were the weakest tissues ingested by all four primates on average, while mid-ranked leaves were the toughest tissues ingested by the four study species. However, the toughness of all selected foods was statistically comparable among the primate species. Preliminary data reveal consistent chewing rates among the monkeys (approximately 0.35 seconds per chewing cycle), but differences exist in the number of times a given item is chewed before swallowing. These findings suggest that leaf eating primates process foods of comparable toughness in different ways, which may relate to differences in craniodental morphology. Funded in part by the CU Museum�s Burt Fund, CU Anthropology Department, Zoological Society of San Diego, and National Geographic Society.