John E.A. Bertram

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We measured the lengths and diameters of four long bones from 118 terrestrial carnivoran species using museum specimens. Though intrafamilial regressions scaled linearly, nearly all intraordinal regressions scaled non-linearly. The observed non-linear scaling of bone dimensions within this order results from a systematic decrease in intrafamilial allometric(More)
Nearly all long bones of terrestrial mammals that have been studied are loaded in bending. Yet bending requires greater bone mass than axial compression for effective support of equivalent static loads. Most long bones, in fact, are curved along their length; their curvature augmenting rather than diminishing stresses developed due to bending. The most(More)
An engineering fracture mechanics approach was applied to the analysis of the fracture resistance of equine hoof-wall. The relationship between fracture toughness and the morphological organization of the keratin hoof tissue was investigated. Fracture toughness was evaluated using the J-integral analysis method which employs the compact tension test(More)
Tensile moduli and J-integral fracture toughness values were determined for horse hoof-wall keratin at four hydration levels. The stiffness of hoof-wall was influenced by water content to a greater degree than is the stiffness of other mammalian hard keratins. Young's modulus increased from 410 MPa at 100% relative hydration (RH) to 14.6 GPa at 0% RH.(More)
The limbs of growing chicks (2-12 wk of age) were subjected to differing conditions of mechanical use to examine the effect of extrinsic loading on bone modeling early in postnatal growth. One group of chicks was subjected to intensive exercise by running on a treadmill 5 days/wk at 60% maximum speed while carrying on their trunk a load equal to 20% of body(More)
The slender elongated form that is characteristic of the forelimb long bones of gibbons (Hylobates) has long been attributed to their functional adaptation to habitual armswinging locomotion, although potential selective advantages of this morphology for brachiation have yet to be demonstrated. If the forces exerted on the limb skeleton during brachiation(More)
Bones are believed to alter their shape in response to changes in tissue strains produced by physical activity and the goal of this study is to examine whether modeling responses of a growing bone to changes in physical exercise are adjusted to maintain a uniform distribution of functional strains. We test this idea by comparing in vivo strains recorded in(More)
In the evolution of flight bats appear to have suffered a trade-off; they have become poor crawlers relative to terrestrial mammals. Capable walking does occur in a few disparate taxa, including the vampire bats, but the vast majority of bats are able only to shuffle awkwardly along the ground, and the morphological bases of differences in crawling ability(More)
In this study an in vitro analysis of the force and mechanical work required to bite prey items of different size and physical character is combined with an in vivo analysis of prey-handling behavior in the tokay gecko (Gekko gecko). The force required to bite and the work of biting increase with prey size, but the rate of increase is prey specific, with(More)