Rapid behavioural responses of native frogs caused by past predation pressure from invasive mongooses

Komine, H., Fukasawa, K., Akasaka, M., Watari, Y., Iwai, N. and Kaji, K. (2020), Rapid behavioural responses of native frogs caused by past predation pressure from invasive mongooses. Journal of Zoology, vol. 310, pp. 126-134. https://doi.org/10.1111/jzo.12734

 

It is well known that strong predation pressure by invasive predators cause native prey populations to decline. However, few studies have reported invasive predators induce evolutionary changes in a native prey in a short time scale. This could be because strong predation pressure by invasive species often causes the extinction of native prey before an evolutionary effect can be detected.

Figure 1. Invasive mongooses (Herpestes auropunctatus) native to southern Asia are highly problematic invasive species worldwide. Photo by Yuji Obara

Figure 2. Invasion history of invasive mongooses. They were introduced to Amami Island in Japan in 1979 and expanded concentrically. Although the mongooses did not expand to the southern part of the island, they caused significant population declines of native fauna in the invaded area. In 2000, the Ministry of the Environment started an eradication project and the project resulted in significant recovery of native fauna. Photo by Yuji Obara

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 the invasive mongoose (Herpestes auropunctatus) on Amami Island, Japan.

Figure 3. Amami tip-nosed frog (Odorrana amamiensis) is an endangered species that inhabits only the Amami Island and its adjacent island. This species was seriously reduced by the invasive mongoose, however the eradication project led to recovery of this species. Photo by Hirotaka Komine

The native frog population was reduced by the mongoose; however, the eradication project by Ministry of the Environment Japan led to the recovery of the native frog populations, thereby providing an opportunity to evaluate the evolutionary impact of the invasive species. We hypothesised that spatial differences in flight initiation distance (FID) between frog populations can be explained by the spatial patterns of past mongoose predation pressure. We measured FID in 278 frogs at sites with different history of mongoose invasion.

Figure 4. Image of the field examination on a forest road. We measured the distance at which the animal began to flee from an approaching researcher.

We found that the native frog became more sensitive to the approach of a potential predator as the historical impact of the mongoose increased. This result suggests that past strong predation pressure by the mongooses drove a rapid behavioural response in the native frog. Our study suggests that such 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.

Fig. 5 We found that the native frogs became more sensitive to a potential predator with increasing past impacts from the invasive mongoose. This result suggests that past strong predation pressure by the mongoose drove a rapid behavioural response in the native frog.

Hirotaka Komine