How Food Geometry and Toughness Influence Ingestive Patterns in Lemurs.

We investigate the extent to which food toughness, geometry, and/or lemur species determine biting locations during feeding. We quantified biting locations in two sympatric species, Lemur catta and Propithecus verreauxi, in Beza Mahafaly Special Reserve, Madagascar. Using video of seven lemur groups, we assigned biting locations to anterior, intermediate, or posterior positions. Food toughness (average and maximum) was measured using a portable field tester. Foods were categorized into four shape (flat, not-flat) and size (small, large) categories. Multinomial logistic regression models were used to test these predictors with food placement as the response. Toughness and food geometry significantly influenced biting positions, though not necessarily as predicted. P. verreauxi favored anterior placements for small, non-flat foods, whereas L. catta favored intermediate, and both used posterior with increasing food toughness. P. verreauxi has a robust masticatory system and can process "moderate" tough food anteriorly (initially defaulting to this position). However, they process food posteriorly as the food increases in toughness. L. catta more evenly distributes bites among the ingestion locations. These two lemur species differ in initial feeding behaviors that are likely related to underlying differences in masticatory morphology.