Seasonality and site specificity of mechanical dietary patterns in two Malagasy lemur families (Lemuridae and Indriidae)

Relationships between tooth morphology and physical food properties are well established Because food breakdown is initiated by the dentition, one may posit that variations in tooth form are related functionally to the physical demands placed on them by the diet. Yet classification of diets as leaves, fruits, and insects does not adequately describe foods in mechanically significant ways. Furthermore, physical dietary properties have not been well quantified. I describe patterns of two physical food properties-hardness and shear strength-in the diets of five lemur taxa in Madagascar-Propithecus diadema edwardsi, Lemur fulvus rufus, and Lemur rubriventer-in the rain forest site of Ranomafana National Park and Propithecus v. verreauxi and Lemur catta at the dry forest site of Beta Mahafaly special reserve. I compared mean plant values for each lemur taxon, the most stressful foods eaten and the amount of time spent feeding on each dietary item. Variation in food hardness is a site phenomenon with fluctuations within sites. Shear strength is strongly seasonal. Lemur diets, as traditionally classified, are not mechanically uniform since frugivores and folivores could be separated on the basis of the physical properties of their foods. Finally, I assign taxa to dietary categories that are mechanically descriptive and derive several predictions regarding expected tooth morphologies from them.