Department of Biology, Indiana State University, Indiana, United States
Background/Question/Methods
Predators and prey have variable amounts of information concerning each other and their interactions. This variability in information may impact the ability of predators to hunt and the ability of prey to avoid death. We hypothesized that frog calls could alter the amount of auditory information available to prey and/or predators and therefore influence prey behavior. Specifically, we predicted that when exposed to spring peeper calls (Pseudacris crucifer) mice (Peromyscus leucopus) would exhibit increased defensive responses due to their reduce ability to detect predators such as owls and canids, or mice would exhibit decreased defensive responses due to the reduced ability of predators to detect mice. Over the course of 120 nights in Terre Haute Indiana, 5 groups of 4 individually PIT-tagged mice lived in an outdoor enclosure. The enclosure contained foraging stations with millet mixed evenly in sand. On a given night we played spring peeper calls at: high volume, low volume, or zero volume (no frog calls). We used optimal foraging theory to measure the defensive responses of the mice. We measured giving up densities (GUDs), time allocation to foraging, apprehension (vigilance), and resource handling strategy (eat seeds where they are found or collect and consume them elsewhere).
Results/Conclusions
We found differences in prey defensive behaviors between the no frog call treatment and the 2 frog call treatments. In the presence of frog calls mice had: lower GUDs, increased time allocation to forging, and exhibited less apprehension. We did not find a difference in foraging strategy. Essentially mice behaved as though the world was safer when frogs were calling. This could be due to the possibility that fog calls make it harder for predators to detect mice and the mice can respond to this change in risk. Thus, frogs are increasing safety for the mice, in the form of acoustic camouflage. In reality, the frog calls likely change the available information for both mice and their predators, but this change in information advantages the mice and disadvantages the mouse predators. In this interaction, the frogs are commensalistic with the mice, and amensalistic with the mouse predators.
