Comparing apples and oranges - The influence of food mechanical properties on ingestive bite sizes in lemurs

Previously we found that Maximum Ingested Bite Size (V_b) - the largest piece of food that an animal will ingest whole without biting first - scales isometrically with body size in 17 species of strepsirrhines at the Duke Lemur Center (DLC). However, because this earlier study focused on only three food types (two with similar mechanical properties), it did not yield results that were easily applied to describing the broad diets of these taxa. Expressing V_b in terms of food mechanical properties allows us to compare data across food types, including foods of wild lemurs, to better understand dietary adaptations in lemurs. To this end, we quantified V_b in five species of lemurs at the DLC representing large and small frugivores and folivores using ten types of food that vary widely in stiffness and toughness to determine how these properties relate to bite sizes. We found that although most species take smaller bites of stiffer foods, this negative relationship was not statistically significant across the whole sample. However, there is a significant relationship between bite size and toughness. All three of the more frugivorous taxa in our sample take significantly smaller bites of tougher foods. However, the two more folivorous lemurs do not. They take small bites for all foods. This suggests that the species most adapted to the consumption of tough foods do not modulate their ingestive sizes to accommodate larger pieces of weak foods.