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Cats fed by humans prey on endangered species -Revealing how cats living in human residential areas are affecting the natural environment-


Article title

Predation on endangered species by human-subsidized domestic cats on Tokunoshima Island

Author (affiliation)

Tamao Maeda(a), Rumiko Nakashita(b), Kazumi Shionosaki(c, d), Fumio Yamada(b), Yuya Watari(b)

(a) Wildlife Research Center, Kyoto University, Kyoto, Japan.

(b) Department of Wildlife Biology, FFPRI, Tsukuba, Ibaraki, Japan.

(c) Amami Wild Animal Research Center, Tatsugo, Kagosima, Japan.

(d) Amami Wildlife Research Center Co. Ltd., Amami, Kagoshima Japan.

Publication Journal

Scientific Reports, 9,16200, November 2019 DOI:10.1038/s41598-019-52472-3( External link )

Content introduction

Cats are one of the most familiar companion animals for humans. Simultaneously, they are also known to be an invasive alien species, reducing the population of indigenous species and causing extinctions across the globe. Indeed, the International Union for Conservation of Nature (IUCN) has designated the cat as one of the world’s worst invasive species. In Japan, there has been increasing social awareness regarding cats being an environmental threat as per reports obtained from across the country regarding cats preying on the indigenous species.

In the present study, we conducted an investigation in Tokunoshima Island, Kagoshima Prefecture (a nominated world natural heritage site) to explore how humans are associated with the impact caused by cats on indigenous species. This island is inhabited by rare endangered species (e.g., special natural monuments and natural monuments), including Amami rabbits (Pentalagus furnessi), Ryukyu long-haired rats (Diplothrix legata), and Tokunoshima spiny rats (Tokudaia tokunoshimensis). The predation on these rare species by cats has become a huge problem (photos). Tokunoshima Island is characterized by its close proximity to the habitats of rare species and those of humans. In fact, Amami rabbits are sometimes observed at the forest edge just behind human houses.

In this study, we collected feces and body hair from captured cats and investigated their foraging habits based on the fecal content analysis and stable isotope ratio analysis of the body hair samples. These analyses were respectively conducted to reveal what they had eaten in several days prior to capture and to clarify what they had been primarily eating in the past several months.

Consequently, the content analysis revealed that approximately 20% of the cats captured in the forest area had preyed on forest animals, including six endangered species: the Amami rabbit, Ryukyu long-haired rat, Tokunoshima spiny rat, Ryukyu robin (Erithacus komadori), Amami tip-nosed frog (Odorrana amamiensis), and native shrews (Crocidura spp.). Meanwhile, the stable isotope ratio analysis found that approximately 70% of their body consisted of pet food. In other words, cats that were ordinarily feeding on pet food entered the forests and preyed on the endangered species (Figure). These cats are believed to be free-ranging owned cats or unowned stray cats. Conversely, the stable isotope ratio analysis also demonstrated that some of the cats captured near human residences had eaten forest animals in the past few months. This suggested that cats observed around human houses are actually moving to and from human habitats and forests.


Photo: (a) A cat caught an Amami rabbit Photo:(b) A cat caught a Ryukyu long-haired rat

Photos captured in Tokunoshima Island: (a) A cat caught an Amami rabbit (photograph provided by Okinawa Amami Nature Conservation Office, Ministry of the Environmet); (b) A cat caught a Ryukyu long-haired rat (photograph taken by Watari & Kazato).


Figure: An image representing the impact
Figure: An image representing the impact on endangered species caused by feeding cats. A cat fed by a human enters a forest and preys on endangered species.