Ontogeny of feeding performance and biomechanics in coyotes

Developing organisms must reconcile conflicts between demands of survival within the current life-history stage, with those of maturation, while negotiating the transitions through succeeding stages. In the case of feeding performance, the parts of the feeding apparatus and their biomechanics must maintain functional integrity to meet the feeding needs of a juvenile even as they develop toward their adult form. We concurrently examine the ontogenetic relationships of feeding performance, dentition and feeding biomechanics, relative to key life-history events, utilizing samples drawn from the same population of known-age coyotes Canis latrans. The development of feeding performance is asynchronous with development of both feeding biomechanics and skull morphology; feeding performance lags during ontogeny despite surprisingly large early mechanical advantage of the temporalis, due in part, to early relative maturity of mandibular shape. Feeding performance and biomechanics, like skull morphology, mature well after weaning at 6 weeks of age. Late maturation of bite strength and feeding performance is mediated by ongoing and continued growth of the temporalis muscles as measured by maximum zygomatic arch breadth (ZAB). Males and females may resolve developmental conflicts differently, as females trade earlier maturity for smaller maximum ZAB, decreased relative bite strength and diminished feeding performance, compared with males. The asynchrony of feeding performance development seen in coyotes, is also characteristic of a highly specialized carnivore, the spotted hyena, but coyotes have a much less protracted development, being handicapped relative to adults for a much shorter time. This developmental asynchrony between feeding performance and morphology suggests that a certain minimum threshold of physical growth and development, together with the associated development of biomechanics, are required to produce effective mastication. The relationships among biomechanics, life-history schedules and ontogeny of feeding performance have obvious implications for fitness.