1. Bite force is used to investigate feeding performance in a variety of vertebrates. In all taxa studied, bite force is strongly correlated with body and head size. Studies of bite force in bats have largely centred on neotropical species with a particular focus on species that maximize dietary differences. Little is known about the bite force of bats from the Old World tropics, nor of variation in bite force within diverse assemblages of obligate insectivores. Moreover, factors other than size are poorly known but may be important in driving interspecific differences in bite force, and thereby diet. 2. Here, we examine the correlation between morphological variation and bite force of 35 species of insectivorous bats from a single palaeotropical assemblage. We confirmed the overall relationship between size and bite force across species, but found that bite force is predicted more strongly by head length than body mass or forearm length. 3. From the combined action of jaw muscles and muscle-bone mechanisms, bats generate a mechanical advantage that creates pressure during biting. We calculated the size-independent mechanical advantage for each of five mandible lever systems (three delineated by the temporalis muscle and two delineated by the masseter muscle) operating through three function points (molar, canine and incisor). Size-independent mechanical advantage of the suprazygomatic portion of the temporalis muscle at the molar function point was the only significant predictor of size-independent maximum bite force across all species. 4. Within families, the size-independent mechanical advantage of the superficial portion of the masseter muscle plays a significant role in predicting size-independent maximum bite force in both the Rhinolophidae and Vespertilionidae. For the family Hipposideridae, however, sizeindependent mechanical advantage showed no role in predicting size-independent maximum bite force, suggesting that size really matters in predicting the maximum bite force capacity for this family.

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Differences in wing morphology are predicted to reflect differences in bat foraging strategies. Experimental tests of this prediction typically assess the relationship between wing morphology and a measures of flight performance on an obstacle course. However, studies have lacked measures of obstacle avoidance ability true scores, which may confound interpretation of ability across the range of presented tasks. Here, we used Rasch analysis of performance in a collision-avoidance to estimate the ability of bat species to fly through vegetative clutter. We refer to this latent trait as clutter negotiating ability and determined the relationships between clutter negotiating ability and wing morphology in 15 forest insectivorous bat species that forage in the densely-cluttered rainforests of Malaysia. The clutter negotiating ability scores were quantified based on individual responses of each species to 11 different obstacle arrangements (four banks of vertical strings 10 - 60 cm apart). The tasks employed for the collision-avoidance experiment were reliable and valid, although Rasch analysis suggested that the experiment was too easy to discriminate completely among the 15 species. We found significant negative correlations between clutter negotiating ability and body mass, wingspan, wing loading and wing area but a positive significant correlation with wingtip area ratio. However, in stepwise multiple regression analyses, only body mass and wing loading were significant predictors of clutter negotiating ability. Species fell into clusters of different clutter negotiating ability, suggesting a potential mechanism for resource partitioning within the forest interior insectivorous ensemble.