Meeting Abstract

35.1  Friday, Jan. 4  Sexual dimorphism in the Gray Wolf (Canis lupus): specialization for male-male competition or for male provisioning? MORRIS, J.S.*; BRANDT, E.; University of Utah; University of Utah

Sexual selection theory predicts that male mammals will be more specialized for physical competition than females. Specialization for aggression, however, may result in functional conflicts with locomotor demands. Characters associated with locomotor economy include long, gracile limbs that reduce the cost of transport by increasing stride length and decreasing the energy required to swing the limbs. In contrast, specialization for aggression appears to result in stout bones and large distal muscles with high mechanical advantage that increase force available to strike or manipulate opponents. Gray wolves (Canis lupus) are highly cursorial animals, traveling immense distances to locate and run down prey. Gray wolves also aggressively defend territory through direct competition and kill much larger, highly dangerous prey species. Because both sexes actively participate in these activities, a low level of musculo-skeletal sexual dimorphism is expected. However, males often lead in aggressive encounters with conspecifics and, for a period during the mating season, must kill prey without the assistance of the dominant female to provision her and their young. Thus, male wolves may exhibit a higher degree of morphological adaptation associated with aggressive activities. To assess sexual dimorphism in three distinct subspecies of gray wolves, a series of skeletal metrics were taken from fresh cadavers and museum specimens. All measures were size-corrected and analyzed to detect relative differences in size and shape. Males were found to have broader skulls, more robust limb bones, and higher muscle mechanical advantages than females, suggesting that males are more highly specialized for physical aggression. However, results for each subspecies differed substantially, likely reflecting differences in selective pressures on pursuit versus handling capabilities based on prey size.