Predator, but not conspecific, chemical cues influence pond selection by recently metamorphosed Iberian green frogs, Rana perezi

In amphibians, adults and larvae have different ecological requirements that could force recently metamorphosed individuals to disperse. The presence of chemical cues of conspecifics and predators could provide information about habitat quality, which might influence the juveniles’ settlement decisions. We examined in the laboratory whether pond choice by recently metamorphosed Iberian green frogs ( Rana perezi Seoane, 1885) is influenced by the presence of chemical cues from conspecifics and (or) from predators in the water. Our results suggest that frogs were able to detect the presence of chemical cues of snake predators in the water and that they avoided entering such ponds. However, frogs did not show either attraction or avoidance of ponds with conspecific chemical cues. Thus, juvenile frogs may select their postmetamorphic territories based on the lack of predation risk, and possibly on some habitat features, but not on the presence of conspecifics.

Factors affecting escape behavior of Iberian green frogs (Rana perezi)

Theoretical models and empirical evidence suggest that prey should not flee immediately upon detecting an approaching predator, but instead should adjust their escape response to minimize the costs of flight. Similarly, after deciding to escape, animals should tend to adjust the magnitude and characteristics of their escape response according to the perceived level of predation risk. Although these hypotheses have been tested in some prey types, it remains for their applicability to a wider range of taxa to be ascertained and for a larger variety of microhabitat and environmental conditions to be considered. We simulated predator approaches to Iberian green frogs (Rana perezi Seoane, 1885) in the field. Frogs were approached while they were foraging alone at the edge of water, and they escaped by jumping into the water. Results showed that escape decisions of frogs are influenced by microhabitat variables and body size. Both the approach distance allowed to the predator and the distance jumped by the frogs in response to the approach were positively correlated with the initial distance of the frog from the water's edge; they were also dependent on vegetation cover at the edge of and in the water. Small frogs appeared to rely on crypsis more than large frogs and allowed shorter predator approach distances. They also remained still on the water surface after jumping more often than large frogs. We conclude that such flexibility in the escape response may allow frogs to reduce predation risk without incurring excessive costs.