Endocranial volume increases across captive generations in the endangered Mexican wolf

Abstract

Endangered animals in captivity may display reduced brain sizes due to captive conditions and limited genetic diversity. Captive diets, for example, may differ in nutrition and texture, altering cranial musculature and alleviating constraints on cranial shape development. Changes in brain size are associated with biological fitness, which may limit reintroduction success. Little is known about how changes in brain size progress in highly managed carnivoran populations and whether such traits are retained among reintroduced populations. Here, we measured the endocranial volume of preserved Mexican wolf skulls across captive generations and between captive, wild, and reintroduced populations and assessed endocranial volume dependence on inbreeding and cranial musculature. Endocranial volume increased across captive generations. However, we did not detect a difference among captive, wild, and reintroduced groups, perhaps due to the variability across captive generations. We did not find a relationship between endocranial volume and either inbreeding or cranial musculature, although the captive population displayed an increase in the cross-sectional area of the masseter muscle. We hypothesize that the increase in endocranial volume observed across captive generations may be related to the high-quality nutrition provided in captivity.

Getting to the Meat of It: The Effects of a Captive Diet upon the Skull Morphology of the Lion and Tiger

“…While it has been suggested that the smaller cranial volume of captive lions is pathological [20], it could also be related to the development of jaw musculature impacting skull development, as well as the complexity of the environment impacting brain development. Conversely, cranial volume may be influenced by nutrition, and the Mexican wolf (Canis lupus baileyi) has been shown to have increased cranial volume in captivity, likely as a consequence of diet [80]. Contrary to other lions and tigers, captive Asian lions have been shown to have larger cranial volumes than wild Asian lions, which may be affected by differences in diet [81].…”