Meeting Abstract

44.5  Wednesday, Jan. 5  Tail use in primates: balancing the variables MILLER, CE*; SCHMITT, D; Duke University; Duke University charlotte.miller@duke.edu

The biomechanical role of the tail during animal locomotion is poorly understood, in part because tails are also often used in other complex non-locomotor behaviors such as signaling. Data are available on the role of the tail in weight bearing (prehension) during locomotion, but reports of tail use for maintaining balance are, for the most part, anecdotal. Our aim is to assess the importance of the tail in modulating fluctuations in, or changing the location of, whole body center of mass in the vertical and fore-aft planes. In this study we quantify tail shape and position during quadrupedal locomotion for a wide range of arboreal and terrestrial primates moving on either flat ground or a raised horizontal pole. The angle and height of the proximal and distal portions of the tail are measured relative to the tail base. We have found that irrespective of phylogeny, anatomy, and preferred locomotor substrate, tails are moved very little during walking. Instead the tail is placed in a position and remains relatively fixed in space in the vertical and fore-aft planes. Variability increases in some primates at higher speeds and when pole size is very small. Movements in the tail base (and hence body) have little effect on overall tail position, which suggests that active mechanisms may isolate tail movements from those of the body. Our findings suggest that it may be possible to separate the components of tail motion related to signaling from those involved in locomotion.