Abstract
It is important to unravel how invasive species impact native ecosystems in order to control them effectively. The presence of abundant exotic prey promotes population growth of invasive predators, thereby enhancing the predation pressure on native prey (hyper-predation). Not only the exotic prey but also feeding by humans is likely to cause “hyper-predation”. However, the contribution of artificial resources to this was underestimated in previous studies. Here, we combined fecal and stable isotope analyses to reveal short- and long-term food habits of free-ranging cats on Tokunoshima Island. Although 20.1% of the feral cat feces contained evidence of forest-living species, stable isotope analysis suggested that the cats were mostly dependent on artificial resources. In addition, a general linear model analysis showed that their diet was strongly correlated with landscape variables. These results indicate that the invasive free-ranging cats are aided by anthropogenic feeding, and they move from the human habituated area to natural areas with high biodiversity. These findings suggest the possibility of human feeding indirectly accelerates the effect of cat predation, and call for a further study on their demography. Cat management mainly involves trapping, but our findings show that educating local residents to stop feeding free-ranging cats and keeping pet cats indoors are also important.
Highlights
It is important to unravel how invasive species impact native ecosystems in order to control them effectively
This study evaluated the diet of free-ranging cats on Tokunoshima Island to verify our hypothesis that both “feral” and “stray” cats are accessible to the forest and the residential area and they are highly dependent on the human-provided resources, they predate endemic species in the forest
Six threatened species were detected in 13.5% of the fecal samples: Ryukyu robins (Erithacus komadori komadori), which are endemic to southern Japan[40], and Amami rabbit, Ryukyu www.nature.com/scientificreports long-haired rat, Tokunoshima spiny rat, Crocidura spp., and Amami tip-nosed frog (Odorrana amamiensis), which are endemic to the Ryukyu Islands[41]
Summary
It is important to unravel how invasive species impact native ecosystems in order to control them effectively. A general linear model analysis showed that their diet was strongly correlated with landscape variables These results indicate that the invasive free-ranging cats are aided by anthropogenic feeding, and they move from the human habituated area to natural areas with high biodiversity. The introduced prey and direct or indirect feeding by humans support cat populations and enhance predation pressure on native species, thereby accelerating their extinction[10,21,22,23]. Tokunoshima Island is located in southwestern Japan and is a biodiversity hotspot with unique biota that evolved in the absence of native mammalian predators[25] On this island and adjacent Amami-Oshima and Okinawa Island, free-ranging cats prey on endangered endemic species, such as Amami rabbit (Pentalagus furnessi), Ryukyu long-haired rat (Diplothrix legata), and spiny rat
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