Escape strategy and vocalization during escape by American Bullfrogs (Lithobates catesbeianus)

American bullfrogs, Lithobates catesbeianus, escape by jumping into water and submerging, often vocalizing as they flee. I studied effects of several risk factors on escape and refuge use and the association between vocalization by fleeing frogs and escape by other individuals nearby. Frogs on shore permitted equally close approach when approached along the shore or on a path perpendicular to shore. Frogs in water were more likely to flee when closer to shore and when approached more rapidly. Time spent submerged after fleeing was uncorrelated with proximity of the predator upon escape. Frogs spent longer submerged when they swam along shore away from the point of entry than when they surfaced directly offshore. Neither distance offshore nor Euclidean distance from the entry point upon emergence was related to time spent submerged. Bullfrogs may use unpredictability of distance and direction moved underwater and of duration of submergence as a strategy that reduce risk upon surfacing. When a focal frog vocalized as it fled, immediate escape by nearby nonfocal frogs was more frequent than when focal frogs (1) escaped without vocalization and (2) neither escaped nor vocalized. These findings are consistent with either alarm calling or benefit to the fleeing individual due to brief delay of attack by a predator. They are inconsistent with several other possible functions of calling during escape. Experimentation is needed to definitively test the hypothesis that calls during escape are alarm signals.