Chemically Mediated Fright Response in Southern Toad (Bufo terrestris) Tadpoles

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Laboratory experiments were used to determine whether groups of southern toad (Bufo trresris) tadpoles alter their activity levels and use of refugia when exposed to chemical, but not visual, cues from predacious, two-toed amphiuma (Amphiuma means) and eastern lesser sirens (Siren intermedia intermedia). Amphiuma and sirens hunt by tactile cues. Also explored was the effect of the predator's diet on the behavior of tadpoles and the tadpole's reaction to an extract of crushed toad tadpoles. Predator-avoidance behavior may occasionally cause some prey to erroneously react to predators that find the prey species distasteful. To examine this behavior, this study tested the tadpole's reaction to warmouth sunfish (Lepomis gulosus) an organism that preys on many tadpoles but not distasteful toad tadpoles. Although many tadpole species school, behavioral tests of tadpoles are often carried out using single tadpoles. Therefore, the effect of group size on tadpole antipredatory behavior was also explored. Tadpoles decreased their activity levels when exposed to water that had been in contact with sunfish but not sirens, amphiuma, or southern leopard frog (Rana utricularia) tadpoles. The tadpoles' response to sunfish may be adaptive in that naive fishes must sample toad tadpoles to learn that they are distasteful. Tadpoles were able to differentiate between predators (sirens and amphiuma) fed toad tadpoles and predators fed leopard frog tadpoles. The size of tadpole groups influences their response to predators. Tadpoles in groups of eight and 20 decreased movement to a similar degree, but lone and paired tadpoles moved even less, often freezing during an entire trial. Future antipredatory behavioral tests of tadpoles that school should be performed on groups of more than two tadpoles. ORGANISMS that are able to detect predators at a distance may be less susceptible to predation. Similarly, the ability to differentiate between predacious and nonpredacious heterospecifics may allow an organism to minimize time spent fleeing and maximize time spent foraging, breeding, and socially interacting (Hol