Meeting Abstract

P1.199  Friday, Jan. 4  Mathematical analysis of three-dimensional open water maneuverability by mantas (Manta birostris) KOLPAS, A; FISH, F E*; MEADE, A; DUDAS, M A; MOORED, K W; West Chester Univ., Pennsylvania; West Chester Univ., Pennsylvania; West Chester Univ., Pennsylvania; Dudas’Diving Duds, Pennsylvania; Princeton Univ. New Jersey ffish@wcupa.edu

For aquatic animals, turning maneuvers represent a locomotor activity that may not be confined to a single coordinate plane, making analysis difficult particularly in the field. To measure turning performance in a three-dimensional space for the manta ray, a large open-water swimmer, scaled stereo video recordings (30 fr/s) were collected around Yap, Micronesia. Two video cameras in underwater housings were mounted on tripods and positioned on the bottom at a depth of 24 m around a cleaning station frequented by mantas. The cameras were synchronized by periodic discharges of an electronic strobe. Movements of the cephalic lobes, eye and tail base were tracked to obtain three-dimensional coordinates. A mathematical analysis was performed on the coordinate data to calculate the turning rate and curvature (1/turning radius) as a function of time by numerically estimating the derivative of manta trajectories through three-dimensional space. Tikhonov regularization was used for numerical differentiation that involves the minimization of a cost function with a parameter controlling the balance between data fidelity and regularity of the derivative. The approach gives a much more accurate estimate of the derivative than conventional finite-difference schemes which can amplify noise leading to erroneous results. Data for 30 sequences of rays performing slow, steady turns showed a median turning rate of 46.48 deg/s with a median turning radius of 0.39 body lengths. Such turning maneuvers fall within the range of performance exhibited by swimmers with rigid bodies.