Meeting Abstract
It has long been argued that a number of distinguishing features of primates, including their forward-facing eyes and large binocular visual field, improve the effectiveness of arboreal leaping locomotion, especially in a thin branch setting. This remains an area of intense debate, especially in regards to primate origins, yet this study is the first to directly test the relationship between binocular field size and leaping performance in primates experimentally. The effect of restriction of the binocular field on leaping locomotion was evaluated in five captive Cheirogaleus medius, a small bodied (~175g) nocturnal primate species considered a reasonable morphological and ecological analogue of early primates. Binocular field restriction was achieved using a helmet-mounted blinder that obstructed the medial portion of the visual field of one eye. Subjects were recorded leaping between narrow vertical substrates both with the full use of their binocular field and with a restricted binocular field. Restriction of the binocular field did not increase the subjects’ probability of either missing or failing to reach a landing substrate. Restriction of the binocular field did, however, increase the probability of adverse landings, the number of grasp adjustments individuals made between consecutive leaps, and the lag time between landing and subsequent take-off. These results suggest that increases in binocular field size during early primate evolution may have provided an important advantage in leaping by facilitating more precise landings.
