Meeting Abstract

P2.150  Sunday, Jan. 5 15:30  Specialization for aggression in sexually dimorphic skeletal morphology in Carnivora MORRIS, J.S.*; CARRIER, D.R.; University of Utah; University of Utah j.s.morris@utah.edu

Based on sexual selection theory, male mammals are expected to be more specialized for physical competition than females. Morphological specialization for aggression likely results in several correlated characters. Broad, robust limb bones increase safety factors and provide more surface area for muscle attachment. Large anatomical mechanical advantages about the limb joints increase forces available to strike or manipulate opponents. However, these characters are in conflict with locomotor efficiency because they increase limb mass and inertial forces that must be overcome while cycling the limbs. Thus, a functional trade-off may occur between morphological specialization for economical locomotion and aggression, both of which are ecologically critical activities. In Carnivora, polygyny enforced by male-male competition is the most common mating system. However, variation in social structure (e.g., sociality in Canidae) may lead to differences in the relative importance of aggression. Here we present a large comparative data set on skeletal sexual dimorphism for several morphological characters associated with specialization for aggression. We include data for 27 species from eight families within Carnivora, spanning a large range of body sizes (1 kg to > 200 kg), social systems, and dietary niches. Our results indicate variation in the degree of skeletal sexual dimorphism among carnivores. In several species, males were found to have morphological traits (e.g., larger mechanical advantages about the limb joints, relative to females) consistent with specialization for aggression. In other species, few or no differences were detected. This may be associated with the relative importance of aggression based on mating system and the intensity of male-male competition.