North American River Otters Exhibit Direction Asymmetry in Limb Bone Shape

Abstract

The occurrence of handedness has been widely observed and studied among humans. There is evidence that suggests the asymmetric pressures of using one limb more prominently can have a developmental effect on bone size and shape. The correlation of handedness with directional asymmetry of limb bones has propagated the question of whether this instance also occurs across the animal kingdom, especially within species that use their limbs to move and manipulate objects. Using the North American River Otter (Lontra canadensis), we compared differences in bone size and shape of the left and right limbs. The assessments were made by taking a variety of length and width measurements, as well as integrating 3D geometric morphometrics to compare the bone profiles. Using a t‐test, we found non‐significant (p>.05) differences in the length and width measures of the left and right bones. However, results of an ANOVA on Procrustes aligned shape coordinates indicate significant (p<.05) differences in bone shape. Our results suggest that the shape of left and right limb elements in both the forelimb and hindlimb illustrate directional asymmetry. Future research will provide insight as to whether the shape asymmetry is a product of handedness or other environmental factors.