Development of bite strength and feeding behaviour in juvenile spotted hyenas (Crocuta crocuta)

Abstract

Bite strength is of great importance to carnivores, as their jaws must produce forces of sufficient magnitude to kill and consume their prey. Spotted hyenas, well known for crushing and consuming bones, were studied to determine how tooth and jaw growth affect bite strength and feeding behaviour. Nine captive individuals, aged 6 months to 2 years of age, were sampled as they grew. At 8- to12-week intervals, morphological measurements that estimated jaw muscle mass, tooth size and skull size were taken. Using a force transducer, bite force was measured directly for these juveniles as well as other captive individuals of different ages. In addition, feeding behaviour and performance were quantified periodically by bone tests in which individuals were offered a sheep femur for 15 min. Behaviour and performance were expected to change with the shift from juvenile to adult dentition. Results were not entirely as expected. Morphological measurements of growth reached a plateau at about 20 months, whereas bite strength increased in a linear fashion up to 5 years of age. A fundamental change in tooth use during bone cracking followed the replacement of deciduous teeth with permanent teeth; the primary area of tooth use moved from anterior to rearmost premolars, increasing the mechanical advantage of the jaw adductors. The timing of this shift seemed to be a function of a decrease in gape limitation as a result of growth as well as caudal movement of the premolars. Our data demonstrated that juvenile hyenas had not achieved adult feeding performance levels at 12 months of age, when they are typically weaned in the wild. This suggests that recently weaned cubs may be at an increased risk of starvation and that selection might favour later weaning times.