Department of Evolutionary Anthropology, Duke University
Friday All day, Park Concourse
Many primate species show remarkable morphological adaptations to anterior tooth use, but the mechanics of this activity are poorly understood. Currently, in vivo data on bite force generation during anterior tooth use in primates are restricted to isometric bite forces on a force transducer and one study of bite kinetics for the mandible during wood-gouging in Callithrix jacchus. This research expands this area by collecting data on mandibular bite reaction forces from two aye-ayes gnawing an instrumented hardwood block. Subjects produced peak superior-inferior (SI) bite reaction forces of 23.6N (SD=9.3), peak anterior-posterior forces of 35.5N (SD=16.4), and peak resultant bite reaction forces of 43.7N (SD=11) during 41 gnawing cycles. Gnawing in Daubentonia occurred at a rate of 3.1Hz (SD=0.6), with peak AP forces preceding peak SI forces by 3.8ms (SD=5).
Gnaws recorded for Daubentonia are significantly larger than gnaws reported for Callithrix, which had average peak resultant forces of 28.0N (SD=3.6). Callithrix was reported to use only 50.3% of its maximum SI bite force (measured from isometric transducer bites) during wood-gouging. Transducer bites are unavailable for Daubentonia. Estimates of maximum SI bite force derived from published jaw adductor rPCSAs suggest that Daubentonia may use 10% or less of its vertical bite force capacity during gnawing. These findings suggest that wood-gnawing, like gouging, does not require relatively high bite forces. Further research on the metabolic costs of gnawing and seed predation in Daubentonia are planned to further elucidate the mechanical role of bite force generation and resistance during anterior tooth use.