Tuning of Visuomotor Coordination During Prey Capture in Water Birds

Abstract

In order to perform the necessary motor activities for prey capture, a predator must obtain spatio-temporal information on the orientation and distance of the prey, and on the relative motion between it and the prey (cf. Chap. 13). Predatory acts are useful in the study of visuomotor coordination mechanisms and the means by which they are tuned to achieve optimal direction and timing of movements. “Sit and wait” predatory patterns are especially useful, as they involve relatively distinct motor patterns, are of short duration and are relatively easy to record. A “sit and wait” predator stalks prey slowly, or even keeps motionless until the prey is close enough, and then performs a fast capturing movement (O’Brian et al. 1990). This is often a “point of no return”, after which prey either is captured or escapes. For example, after slowly approaching and aiming at an insect, a chameleon (Chameleo spp.) rapidly “shoots” its long tongue at it. To avoid over- or undershooting of the tongue, distance must be accurately estimated prior to “shooting”, as no motor corrections are performed later (Harkness 1977; Flanders 1985). Predators such as toads, preying mantids and herons, which capture prey using a rapid movement, must perform in a similar manner (Mittelstaedt 1957; Curio 1976; Ewert 1980).