Showing papers by "Martin S. Fischer published in 2008"

Gait parameter adjustments of cotton-top tamarins (Saguinus oedipus, Callitrichidae) to locomotion on inclined arboreal substrates.

Abstract: The influence of different substrate inclinations on gaits and metric gait parameters (relative forelimb and hind limb protraction, relative forelimb, and hind limb retraction, stride length, stance, and swing phase duration) of cotton-top tamarin locomotion was studied using high-speed video films and evaluated by descriptive and analytical statistical methods. As previously shown, lateral sequence gaits predominantly occurred on descending arboreal substrates (branchlike pole with a smaller diameter than the animal's body). Gait sequence patterns display significant dependency on substrate inclination. Cotton-top tamarins utilize lower diagonality values the more the substrate declines. This tendency leads to a greater use of lateral sequence gaits on steeply declined substrates. Conversely, these primates display the tendency to utilize higher diagonality values the more the substrate inclines leading to the predominant occurrence of diagonal sequence (DS) gaits. Duty factor index, extent of relative protraction, and relative retraction of both limb pairs as well as the relation of forelimb stance phase duration to hind limb stance phase duration is also correlated to the inclination of the substrate. Stride length and swing phase duration display no significant dependence on inclination, but are determined by the speed of the moving animal. The relevant duty factor is approximately constant at all inclinations. Integrating our results with results of other authors we propose a hypothesis for the functional relevance of a utilization of lateral sequence gaits in downward locomotion and DS gaits in upward locomotion. Our data support the notion of a wide ranging behavioral plasticity as a general primate locomotor characteristic.

The movements of limb segments and joints during locomotion in African and Asian elephants.

Abstract: As the largest extant terrestrial animals, elephants do not trot or gallop but can move smoothly to faster speeds without markedly changing their kinematics, yet with a shift from vaulting to bouncing kinetics. To understand this unusual mechanism, we quantified the forelimb and hindlimb motions of eight Asian elephants (Elephas maximus) and seven African elephants (Loxodonta africana). We used 240 Hz motion analysis (tracking 10 joint markers) to measure the flexion/extension angles and angular velocities of the limb segments and joints for 288 strides across an eightfold range of speeds (0.6-4.9 m s(-1)) and a sevenfold range of body mass (521-3684 kg). We show that the columnar limb orientation that elephants supposedly exemplify is an oversimplification--few segments or joints are extremely vertical during weight support (especially at faster speeds), and joint flexion during the swing phase is considerable. The 'inflexible' ankle is shown to have potentially spring-like motion, unlike the highly flexible wrist, which ironically is more static during support. Elephants use approximately 31-77% of their maximal joint ranges of motion during rapid locomotion, with this fraction increasing distally in the limbs, a trend observed in some other running animals. All angular velocities decrease with increasing size, whereas smaller elephant limbs are not markedly more flexed than adults. We find no major quantitative differences between African and Asian elephant locomotion but show that elephant limb motions are more similar to those of smaller animals, including humans and horses, than commonly recognized. Such similarities have been obscured by the reliance on the term ;columnar' to differentiate elephant limb posture from that of other animals. Our database will be helpful for identifying elephants with unusual limb movements, facilitating early recognition of musculoskeletal pathology.