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J Comp Physiol A (2009) 195:843852 DOI 10.1007/s00359-009-0463-2
ORIGINAL PAPER
Prey location, biomechanical constraints, and motor program choice during prey capture in the tomato frog, Dyscophus guineti
Jenna A. Monroy Kiisa C. Nishikawa
Received: 3 May 2009 / Revised: 15 July 2009 / Accepted: 15 July 2009 / Published online: 6 August 2009 Springer-Verlag 2009
Abstract This study investigated how visual information about prey location and biomechanical constraints of the feeding apparatus inXuence the feeding behavior of the tomato frog, Dyscophus guineti. When feeding on prey at small azimuths (less than 40), frogs aimed their heads
toward the prey but did not aim their tongues relative to their heads. Frogs projected their tongues rapidly by transferring momentum from the lower jaw to the tongue. Storage and recovery of elastic energy by the mouth opening muscles ampliWed the velocities of mouth opening and tongue projection. This behavior can only occur when the lower jaw and tongue are aligned (i.e., within the range of motion of the neck). When feeding on prey at large azimuths (greater than 40), frogs aimed both the head and
tongue toward the prey and used a muscular hydrostatic mechanism to project the tongue. Hydrostatic elongation allows for frogs to capture prey at greater azimuthal locations. Because the tongue moves independently of the lower jaw, frogs can no longer take advantage of momentum transfer to amplify the speed of tongue projection. To feed on prey at diVerent azimuthal locations, tomato frogs switch between alternative strategies to circumvent these biomechanical constraints.
Keywords Feeding Behavioral choice
Biomechanical tradeoVs Frog Amphibian
Introduction
Many vertebrates feed on a wide variety of prey that diVer in their physical and behavioral characteristics (Schaerlaeken et al. 2007).Thus, animals use diVerent kinematic strategies for capturing diVerent prey (e.g., sharks, Ferry-Graham 1998; Wshes, Liem 1978; Wainwright and Lauder 1986; van Wassenberg et al. 2006; salamanders, Deban 1997; frogs, Anderson 1993; Valdez and Nishikawa 1997; and lizards, Lappin and German 2005). In many animals, visual information about prey size, shape, or location is particularly important for modulating prey capture behavior (parrotWsh, Rice and Westneat 2005; salamanders, Deban 1997, frogs, Anderson and Nishikawa 1996; and lizards Schaerlaeken et al. 2007). For example, the leopard frog, Rana pipiens will apprehend prey with either its tongue...