Meeting Abstract

80-4  Wednesday, Jan. 6 08:45  Divergence of craniodental morphology in southern sea otters LAW, CJ*; BALIGA, VB; MEHTA, RS; Univ. of California, Santa Cruz; Univ. of California, Santa Cruz; Univ. of California, Santa Cruz cjlaw@ucsc.edu http://research.pbsci.ucsc.edu/eeb/cjlaw/

As a species, southern sea otters (Enhydra lutris nereis) are apex predators that consume a wide variety of hard-shelled macroinvertebrates. Recent work, however, suggests that male and females utilize different resources in response to increased population density. Apart from body size, morphological patterns of sexual dimorphism in sea otters are unknown. Females exhibit greater intraspecific dietary specialization than males and this gender difference suggests that sexual dimorphism may influence the functional morphology of feeding in southern sea otters. If intersexual dietary divergence does occur, we would expect to find differences in the feeding apparatus between the sexes. Uni- and multivariate analyses of 22 craniodental traits found that the primary axis of craniodental variation is driven by sexual size dimorphism. In addition, analyses investigating sexual shape dimorphism of the size-independent principal components failed to reject the null hypothesis that no craniodental shape differences occur between the sexes. However, separate ANOVA tests on each size-independent PC suggest subtle shape differences between the sexes. To further examine patterns of intersexual dietary divergence in southern sea otters, we use 2D geometric morphometrics from an ontogenetic series of skulls to investigate differences in cranial growth between female and male otters. Preliminary results suggest that intersexual differences in cranial shape begin to diverge during the transition between the subadult (1.5–2.5 years) and adult (2.5–9 years) age classes.