Rapid responses in morphology and performance of native frogs induced by predation pressure from invasive mongooses

Abstract

Invasive predators often decrease the abundance and distribution of native prey, but only a few studies have reported rapid predator-induced morphological and performance changes. An effective prey performance response may actually depend whether the predator uses a sit-and-wait or an active foraging strategy; the former would require prey to obtain the ability to move quickly in bursts, while the latter would require prey to increase their endurance to survive. The performance of native prey should therefore change according to the predation type of an invasive predator when it differs from that of native predators. As such, it is critical to evaluate prey performance to understand the effects of different predation types. We examined rapid morphological (hind limb length) and performance (burst movement ability, endurance) changes in a native prey frog induced by an invasive predator mongoose on Amami Island, Japan, where the only native predators of the frog are snakes. The hind limb length of the frog increased under the strong predation effect of the mongoose, which may have acted as a selective agent to induce rapid morphological responses. The endurance, but not the burst movement ability, of the frog was higher under the strong effect of predation by the mongoose. This suggests that endurance was a specific target of natural selection and that the performance of the native prey changed in response to the new predation type. Examining not only morphological but also performance changes will allow us to understand in detail the impact of invasive predators.