Southern toads alter their behavior in response to red-imported fire ants

We used the southern toad (Anaxyrusterrestris) as a model species to explore how an invasive species, the red-imported fire ant (Solenopsis invicta; hereafter RIFA), influences amphibian predator avoidance and movement behaviors. Our objective was to determine if toads spent less time near and moved more frequently in the presence of RIFAs compared to pyramid ants by comparing behavioral reactions of toads to RIFAs versus a control and pyramid ants versus a control. Laboratory experiments involved three treatments including no ants, RIFAs, and native pyramid ants (Dorymyrmex bureni) within an experimental arena. We randomly placed ants into one of two containers located at each end of the arena. For each trial we placed a toad into the experimental arena, allowed the toad to acclimate and then recorded its behavior. We calculated the proportion of time the toad spent near ants and the number of movements completed by each toad. Comparing the RIFA treatment to the pyramid ant treatment, toads spent 35 % less time on the half of the experimental arena near RIFAs (P = 0.0304). Toad movements were 1.5 times more frequent in trials with RIFAs than pyramid ants (P = 0.0488). We propose that southern toads associate RIFAs either with increased predation risk or risk of injury compared to pyramid ants. Although the behaviors we observed might lessen the direct effects of RIFAs on southern toads via predation and injury, the indirect effects of increased movement and avoidance of RIFAs could also influence toad fitness by decreasing reproductive and foraging success.