Meeting Abstract

P1.178  Wednesday, Jan. 4  Use of preferred escape trajectories in Bluegill sunfish (Lepomis macrochirus) ELLERBY, D.J.; HITCHCOCK, A.C.*; Wellesley College; Wellesley College

The escape response of a fish must be both rapid and unpredictable to avoid predation. Movement directed away from the predator would seem ideal; however, a fixed escape strategy would allow predators to predict a prey animal’s movements. Conversely, a random strategy would lead to some escape responses being towards the predator, an unsuccessful solution. Large data sets that allow clear resolution of escape trajectory distributions and an assessment of individual variability in escape strategy are not currently available for vertebrates. Individual bluegill sunfish (Lepomis macrochirus) were startled 60 times by a stimulus directed towards the head and their escape trajectory was recorded via high speed camera. The resulting trajectory distribution was multimodal. Similar preferred escape trajectories were found across individuals, occurring at approximately 85o and 140o from their initial orientation. An additional peak at very low angles occurred in some individuals, and some fish expressed “sidedness,” with a preference for either right or left turns. The presence of common peak trajectories suggests that fish choose from a set of preferred angles of escape relative to the direction of the threat, keeping their response unpredictable but also nonrandom. This may keep the variability necessary to confuse predators while reducing the pool of potential choices, allowing a faster response.