Ontogenetic Change in Skull Morphology and Mechanical Advantage in the Spotted Hyena (Crocuta crocuta)

Weaning represents a challenging transition for Young mammals, one particularly difficult for species coping with extreme conditions during Feeding Spotted hyenas (Crocuta crocuta) experience such extreme conditions imposed by intense feeding competition during which the ability to consume large quantities of food quickly is highly advantages As adult Spotted hyenas have massive skulls specialized for durophagy and call feed very rapidly, young individuals are likely at a competitive disadvantage until that specialized morphology is completely developed Here we document developmental changes in Skull size, shape, and mechanical advantage of the jaws Sampling all ontogenetic series of Crocuta skulls from individuals ranging in age from 2 months to 1.8 years, we use linear measurements and geometric morphometrics to test hypotheses suggesting that; size, limited mechanical advantage of the jaws, and/or limited attachment sites for law muscles might constrain the feeding performance of juveniles. We also examine Skull development in relation to key life history events, including weaning and reproductive maturity, to inquire whether ontogeny of the feeding apparatus is slower or more protracted in this species than in carnivores not specialized for durophagy We Find that, although mechanical advantage reaches maturity in hyenas at 22 months, adult Skull size IS not achieved until 29 months of age. and Skull shape does not reach maturity until 35 months The latter is nearly 2 years after mean weaning age, and more than 1 year after reproductive maturity Thus, skull development ill Crocuta. is indeed protracted relative to that in most other carnivores Based oil the Skull features that continue to change and to provide additional muscle attachment area, protracted development may be largely due to development of the massive musculature required by durophagy These findings may ultimately shed light oil the adaptive significance of the unusual role-reversed pattern of female dominance over males in this species J. Morphol 271.353-365, 2010 (C) 2009 Wiley-Liss, Inc