The roles of predator identity and group size in the antipredator responses of American toad (Bufo americanus) and bullfrog (Rana catesbeiana) tadpoles

Prey must integrate several cues to assess predation risk and determine appropriate antipredator responses. Few studies on anuran tadpoles have simultaneously varied multiple cues related to predation risk. We examined how American toad (Bufo americanus) and bullfrog (Rana catesbeiana) tadpoles respond to predator identity (e.g., dytiscid beetle larvae or bluegill sunfish), group size, and, for American toads, tadpole size. American toads were less active in control and with bluegill, and higher with dytiscids. American toads did not alter habitat use with bluegill, but solitary tadpoles avoided vegetation when with dytiscids. American toads in pairs or groups of 8 used vegetation more than solitary tadpoles in the presence of dytiscids. Smaller American toad tadpoles were more active and used open water more than larger tadpoles. Bullfrogs were less active in the presence of either predator relative to the control. Bullfrogs did not adjust habitat use with dytiscids, but used vegetation less in the presence of bluegill. Bullfrogs in groups of 8 were more active than solitary tadpoles or tadpoles in pairs. Group size in bullfrogs affected the response to predator cues. In conclusion, the behavior of tadpoles responds to a variety of factors, including group size, predator cues, and tadpole size.