Trabecular bone morphology in felids reflects diversity in locomotor strategy but not home range size.

A relationship exists between mechanical loading, and the resulting changes in bone morphology. When bones experience increased loading, they undergo change through bone modeling and remodeling in response to loading frequency and strain. Organisms with differing locomotor behaviors are distinguished by differences in limb bone morphology. In other words, an organisms' biological structure such as limb morphology is adapted for its behavior including locomotor strategy. While there are studies showing a relationship between bone morphology and locomotor strategy in a myriad of taxa none of them have specifically investigated felid species occupying disparate geographical spaces. This study investigates trabecular bone morphology (bone volume fraction, BVF and degree of anisotropy, DA) in the femoral and humeral heads and distal tibia of four felid species to identify whether there is a relationship between these bone properties and their locomotor behavior. We test the hypotheses that felid species with large home ranges i.e., cougars and cheetahs will have significantly greater BVF than those with small home ranges (leopards and jaguars) in the forelimb than hindlimb and will exhibit greater DA because non-primate mammals have greater vertical ground reaction forces on the fore-than in the hindlimb. We found no significant differences across species in both the femoral and humeral BVF (p>0.05). Results also showed that in the distal tibia, leopards, cougars and cheetahs have significantly greater (p<0.05) BVF than jaguars. Additionally, humeral and distal tibia DA in the jaguars was significantly greater than in the femur. Interestingly, despite differences in home range size, the proximal limb elements do not reflect differences in BVF, however, the distal most element-the tibia- suggests greater loading among jaguars. In the same vein, humeral and tibia suggest greater stereotypical loading among jaguars. The jaguar results are potentially due to the diversity in locomotor strategy rather than differences in home range size. This implies a cautious approach is warranted in studying how repeated loading influences trabecular morphology and places emphasis on investigating the diversity of locomotor behavior rather than overall loading.