Meeting Abstract

P1.100  Wednesday, Jan. 4  Skeletal sexual dimorphism in Gray Wolves indicates functional trade-offs in specialization for competition versus locomotor economy. BRANDT, E; MORRIS, JS*; CARRIER, DR; University of Utah; University of Utah; University of Utah

Sexual selection theory predicts that male mammals will be more specialized for physical competition than females. Specialization for fighting in males may, however, result in functional conflicts with the locomotor demands that females face. Specialization for locomotion results in a suite of correlated characters; i.e., 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 physical competition appears to result in stout bones and large distal muscles with high mechanical advantage that increase force available to strike or manipulate opponents. In this context, gray wolves (Canis lupus), are interesting because although males are likely subject to sexual selection on male-male competition, both sexes actively participate in the defense of territory and both forage over great distances and run down prey. Thus, a phenotype specialized for efficient locomotion is expected in both sexes and therefore wolves might exhibit a low level of musculo-skeletal sexual dimorphism. To determine whether or not wolves exhibit sexual dimorphism, 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 relatively shorter, more robust limb bones with higher muscle mechanical advantage, while the limbs of females were relatively longer and more slender. These differences are consistent with specialization of males for physical competition, and greater specialization in females for efficient locomotion.