P2.158 Thursday, Jan. 5 Does School Size matter? Swimming Kinematics of Cownose Rays (Rhinoptera bonasus) SICILIANO, AM*; BEDORE, CN; LONG, JH; PORTER, ME; Vassar College; Florida Atlantic University; Vassar College; Vassar College firstname.lastname@example.org
Some groups of animals coordinate their behavior, moving together in swarms or schools. To understand the mechanisms by which schools of fish operate, we investigated cownose rays (Rhinoptera bonasus), one of the few species of elasmobranch fishes known to school. Some models of group behavior predict that the size of the school, as measured by number of individuals, will alter the behavior of the school. Our goal was to test this hypothesis. Specifically, we hypothesized that as the size of the school increases, the school’s mean swimming velocity will decrease while, at the same time, individuals will decrease the distance to their nearest neighbors. We tested schools of 1, 2, 5, and 10 rays in a tank of 5 m diameter. From overhead video, we measured the kinematics of individuals and the group during schooling behaviors that we categorized as swimming, feeding, and escaping. During the swimming trials, the school was left unperturbed for 20 minutes. During feeding, food was placed in the tank at the beginning of the trial and the school was filmed for 20 minutes. For the escape behavior trials, which lasted for 30 minutes, every 5 minutes a single ray at the leading edge of the school was startled. Response variables over the length of the trial included velocity of each individual, the mean velocity of the school, and the mean distance from the nearest neighbor for each individual. The data suggest an increase in velocity during escape and feeding treatments. Preliminary analyses show support for the importance of school size on behavior. In addition, at the largest sizes the school’s behavior is impacted by the physical limits of the tank. This work was funded by the National Science Foundation (IOS-0922605).