Maximum ingested food size in captive anthropoids.

ABSTRACT

OBJECTIVES: Maximum ingested food size (Vb ) is an empirically tested performance variable that can shed light on feeding energetics and adaptation in the masticatory system. Until now, this variable had been tested in strepsirrhines alone among primates. Here, we present the first data on Vb in a broad sample of anthropoid primates and describe scaling patterns. MATERIALS AND METHODS: Vb data on anthropoids were collected under captive conditions at the Philadelphia Zoo and compared with published data on strepsirrhines. Data on Vb were scaled against individual body mass and were compared with experimentally determined toughness and stiffness values for the test foods. RESULTS: Unlike in strepsirrhines, where essentially Vb scales isometrically with body mass, Vb in anthropoids scales with negative allometry. There is a significant effect of food material properties on Vb , although bite size in anthropoids varies less based on food properties than in strepsirrhines. Large folivorous strepsirrhines follow the anthropoid trend in bite size scaling, but large frugivorous ones take especially large bites. DISCUSSION: Negative scaling of bite size in the anthropoids sampled could be due to reduced adaptation for gape. Some early anthropoids likely evolved adaptations for maximizing mechanical advantage and fatigue resistance in the chewing muscles, resulting in reduced gape. This might have channeled them toward smaller bites of more-resistant foods and away from taking large bites. This might also be the case for some folivorous strepsirrhines.