The Effects of Onychectomy (Declawing) on Antebrachial Myology across the Full Body Size Range of Exotic Species of Felidae

SIMPLE SUMMARY: While people are familiar with the practice of declawing domestic cats, it is also performed on non-domesticated species, such as lions and tigers, to extend the period of safe human interaction for entertainment purposes. Although declawing (removing not only the claw itself, but also the bone from which it grows, whether in part or in whole) clearly affects the skeletal system, the impact on the musculature has not been studied. As the mass of an animal increases cubically as a product of its volume, while the areas of its paws only increase as a square, larger cats have higher foot pressures and, therefore, the surgery may have a greater effect on larger cats. In this study, we evaluate the forearms of clawed and declawed cats to investigate the effects of declawing on muscle architecture. We found that the deep muscles that flex the digits, which are the muscles most directly affected by declawing, are significantly lighter (~73%) and less powerful (46–66%) in animals that have been declawed, while other muscles do not make up for these reductions. Thus, declawing has a substantial effect on the muscular capabilities of cats, and because these deficiencies are not compensated for in larger cats, it probably has even more functionally devastating consequences for these species. ABSTRACT: While people are familiar with the practice of declawing domestic cats, “onychectomy”, as it is also known, is also performed on non-domesticated species, including pantherines, to prolong their use for entertainment purposes. Although the surgery (the partial or complete removal of the distal phalanx) has clear osteological implications, its myological effects have never been studied. As the mass of an animal increases cubically as a product of its volume, while the areas of its paws only increase as a square, larger felids have higher foot pressures and, therefore, the surgery may have particularly substantial functional effects on larger cats. In this study, we evaluate the forearms of clawed and declawed non-domestic felid specimens that spanned the body size range of the whole family to evaluate the effects of onychectomy on muscle fiber architecture. We found that the deep digital flexors (the muscles most directly affected by onychectomy) of declawed felids are significantly lighter (~73%) and less powerful (46–66%) than those of non-declawed felids, while other muscles do not make up for these reductions. Thus, onychectomy has a substantial effect on the myological capabilities of cats, and because these deficiencies are not compensated for in biomechanically disadvantaged larger felids, it probably has even more functionally devastating consequences for these species.