Anxiety-like behavior and tectal gene expression in a foraging/predator avoidance tradeoff task using adult African clawed frogs Xenopus laevis

Animals often halt foraging in the presence of predator cues, an ecological phenomenon known as the foraging/predator avoidance tradeoff. Although some have proposed that anxiety may exist in animals exposed to predator cues, few studies have examined whether such interactions lead to anxiety-like behavior in animals other than laboratory rodents and zebrafish. In this experiment, a foraging/predator avoidance tradeoff task was modified using adult male African clawed frogs (Xenopus laevis) and a looming visual predator stimulus to determine if (1) visual predator cues reduce appetitive behavior, (2) visual predator cues lead to predator avoidance behavior, and (3) if visual predator cues alter the abundance of transcripts in the optic tectum known to be modulated in other brain areas during anxiety. Frogs exposed to the predator stimulus did not reduce their food intake, although sweeping, a foraging behavior, was significantly reduced by the predator stimulus. Predator-exposed animals spent significantly more time stationary and entered the predator zone less compared controls. There were no statistically significant changes in relative transcript abundance of anxiety-related peptides between the groups in the optic tectum. Collectively, this tradeoff task was able to induce discrete avoidance and appetitive behaviors that are similar to anxiety-like behaviors observed in other predator avoidance models; however, the effects of visual threats on feeding and anxiety-related transcript abundance requires further study. Significance statement Halting foraging activities to increase vigilance and engage avoidance behaviors has been proposed to play an adaptive role in survival of predator encounters in a number of animal species. Some have proposed that anxiety evolved as a state associated with the engagement of avoidance and antipredator behavior. However, few studies have examined whether such foraging/predator avoidance tradeoffs result in anxiety-like behavior in animals other than rodents. We developed a foraging/predator avoidance tradeoff task in an aquatic frog species to determine if the sight of a looming visual threat interferes with feeding and causes anxiety-like behavior in an amphibian. Our data suggest that some, but not other (feeding, for example), behavioral aspects of foraging/predator avoidance tradeoffs mimic anxiety-like behavior when a visual threat is present. These data contribute to a growing body of literature indicating that anxiety may be an adaptive response to predator threats in non-mammalian species.

Automated summary

Animals often stop foraging when they sense the presence of predators. This study investigated whether such interactions lead to anxiety-like behavior in animals other than rodents and zebrafish. The experiments were conducted using African clawed frogs and a looming visual predator stimulus. The results showed that visual predator cues reduced foraging behavior and led to predator avoidance behavior in the frogs. However, there were no significant changes in anxiety-related peptide abundance in the optic tectum. Further studies are needed to fully understand the effects of visual threats on feeding and anxiety-related behavior in animals.