Rapid behavioural responses of native frogs caused by past predation pressure from invasive mongooses.
Invasive predators not only cause native prey populations to decline but can also induce evolutionary changes in their behaviour in a short time scale. However, few studies have reported these rapid responses. This could be because strong predation pressure by invasive species often causes the extinction of native prey before an evolutionary effect can be detected. Recently, eradication projects successfully removed invasive predators and resulted in the recovery of native prey. We predicted that rapid responses can be detected by evaluating the behavioural traits of native prey populations having different histories of predator invasion. We examined the behavioural responses of a native frog, the Amami tip-nosed frog (Odorrana amamiensis), to an invasive mongoose (Herpestes auropunctatus) on Amami Island, Japan. The native frog population was reduced by the mongoose; however, the eradication project leads to the recovery of the native frog population, thereby providing an opportunity to evaluate the evolutionary impact of the invasive species. We hypothesized that spatial differences in flight initiation distance (FID) can be explained by spatial patterns of past mongoose predation pressure. We used a spatial model based on generalized least squares regression methods to test the effects of potential factors on FID. We then performed model comparison and model averaging. We found that the native frog became more sensitive to the approach of a potential predator as the historical impact of the mongoose increased, suggesting that past strong predation pressure by the mongoose drove a rapid behavioural response in the native frog. Our study suggests that rapid behavioural responses of other native species can be detected not only after successful eradication projects, but also on currently invaded sites with different invasion histories.