Shape Matters: Lemurs Eat Much Bigger Rounded Than Cubic Foods

Evaluations of maximum ingested bite size (V_b)-the largest bite an animal will ingest whole without biting apart first-provide insights into dietary behaviors. Despite extensive V_b research, it remains unclear whether linear gape or oral volume-related to food minimum linear dimensions or maximal volume, respectively-constrains ingestive bites. To that end, this study compares V_b for tricylinders-a spheroidal shape (the intersection of three perpendicular cylinders)-to cubes (the shape used in all previous V_b studies) to test the effect of different linear dimension-to-volume ratios on bite size.

Cube and tricylinder V_b were quantified for 18 lemurs representing nine taxa using the three foods used most extensively in the previous V_b research.

Across all foods, lemurs consumed larger tricylinders than cubes in both linear dimensions and volume. For the softest food, tricylinder V_b is 161% the volume and 139% the maximal linear dimensions of cubic V_b. V_b for both shapes was highly correlated (r² = 0.90-0.96).

Lemurs ingested significantly larger tricylinders than cubes, challenging the assumption in all previous V_b research that cube V_b represents an ingestive maximum. This suggests a strong influence of shape on ingestion and that V_b of tricylinders, a more naturalistic shape, may better approximate ingestive constraints. Alternatively, our findings may suggest lemurs ingest foods based on their maximal linear dimensions-potentially related to limitations on their ability to manipulate large foods-rather than gape or oral volume constraints.