Meeting Abstract

32.5  Wednesday, Jan. 5  Empirical Standardization of Bite-force Performance LAPPIN, A.K.**; JONES, M.E.H.; California State Polytechnic Univ., Pomona; University College London aklappin@csupomona.edu

Essential aspects of measuring animal performance are elicitation of maximum effort and standardization for behavioral variation among trials, so as to capture maximum voluntary performance. Bite force, second only to locomotion in terms of published works, has seen extensive application in studies incorporating performance (e.g., driver of morphological evolution; limiter/facilitator of food resource exploitation; role in territoriality, dominance, mating/reproductive success). The bulk of this research has been on lizards (>30 studies), due in part to their diversity of feeding and reproductive biology, and their experimental tractability. However, the brisk growth of the literature has come at the expense of a lack of standardization among studies. Using a phylogenetically diverse sample of lizards, we examined the effect of two variations in method: (1) bite substrate (i.e., substrate used on force transducer on which animal bites), and (2) bite out-lever (i.e., distance from jaw joint to bite point on tooth row). We found that bite substrate has a strong effect on performance. Bite forces were lower on hard substrates than on soft substrates. The extent of this difference, which varied among taxa, may reflect the increased risk of damage to the feeding apparatus (e.g., teeth) when biting on unnaturally hard substrates. Variation in bite out-lever produces an artifactual increase in the variance of bite force around the sample mean. This complicates statistical comparisons among groups (e.g., populations, sexes, species, studies), and may obscure more subtle though biologically significant patterns. To facilitate cross-study comparisons and maximize the potential of bite force data in integrative studies, researchers must work together to establish methodological standardization.