Effects of exotic mongoose (Herpestes javanicus) on the native fauna of Amami-Oshima Island, southern Japan, estimated by distribution patterns along the historical gradient of mongoose invasion

Abstract

We examined the distribution patterns of native animals on Amami-Oshima Island, southern Japan, along a historical gradient of mongoose establishment and estimated the effects of mongoose on the native fauna. To assess the relative abundance of various grounddwelling animals, we used the following four methods; sensor cameras for exotic mammals, nighttime driving census for nocturnal native vertebrates, line census for ground-dwelling lizards, and adhesive traps for arthropods. The results indicated that seven species with larger body size, including mammals, birds, reptiles, and amphibians, were rarely observed in mongooseinfested area. By contrast, medium-sized animals showed neutral relationships with mongoose establishment. Interestingly, the densities of smaller-sized animals were higher in mongooseinfested area. It could be interpreted that smaller species have increased in abundance through topdown cascades, i.e., decreases in native predators such as frogs and lizards caused by the mongoose have resulted in increases in the abundance of smaller animals. Predation pressures by mongoose and native predators may be canceled out for medium-sized animals, causing neutral responses to mongoose by these animals. This study appears to be the first example that shows the influence of mongoose on a wide variety of native animals. In addition, our findings indicate the importance of considering the food web structure of a recipient ecosystem and contribute to the prediction and assessment of ecological risks caused not only by mongoose, but also by other invasive top predators.

Population structure and landscape genetics of two endangered frog species of genus Odorrana: different scenarios on two islands

“…Regarding the conservation of Ishikawa's frogs, there are multiple ongoing issues for the declining population sizes: habitat loss due to deforestation and development, over exploitation for the pet trade (Kaneko and Matsui, 2011), and predation by the invasive small Indian mongoose, Herpestes javanicus (Watari et al, 2008). However, the influence of these issues causing population declines was not reflected in our results from a genetic aspect.…”

Differential population responses of native and alien rodents to an invasive predator, habitat alteration and plant masting

“…Thus, the natural forests remaining on Amami Island appear to be a core area for the restoration of the endemic rat species. Fortunately, these forests are located far from the release point of the mongoose, and the predatory impact of the invasive mongoose has been relatively low thus far [34]. If the central area of the topdown control by mongooses had overlapped with the natural forests, then the endemic rat species might have been more threatened.…”

“…The small Indian mongoose was introduced in 1979, and it poses a significant predatory threat to the endemic vertebrates [24,34]. Although the main diet of mongooses is insects and mammalian prey occupied only 20% of mongoose pellets on Amami Island [24], there is evidence that mongooses feed on rats.…”

Effect of travel distance, home range, and bait on the management of small Indian mongooses, Herpestes auropunctatus

“…Barun's (2011) review noted intentional worldwide introductions include 64 islands and at least one continental mainland area for controlling rats and venemous snakes. Like most attempts at biological control of vertebrate pests, mongoose introductions have caused substantial threats to or extinctions of native bird, amphibian, reptile and mammal species (Seaman and Randall 1962;Nellis and Small 1983;Roy et al 2002;Yamada 2002;Watari et al 2008). In some regions they have also become sylvatic reservoirs of rabies, leptospirosis, or canine distemper (Blanton et al 2006).…”