Predation impacts of invasive raccoons on rare native species

Sakura Oe,Mariko Sashika,Ayako Fujimoto,Michito Shimozuru,Toshio Tsubota

doi:10.1038/s41598-020-77016-y

Abstract

In Japan, there are concerns that invasive alien raccoons prey on rare native species during their spawning season from late winter to early summer. We investigated raccoon predation impact by examining the predation presence using DNA metabarcoding and extent of predation on rare native species using stable isotope analysis. We captured raccoons in Hokkaido, Japan from April to August in 2018 and 2019. We analysed raccoon faeces and gastric contents by DNA metabarcoding to detect the rare native Hokkaido salamander and Japanese crayfish. Hokkaido salamanders were detected from gastric contents, but Japanese crayfish were not detected in any samples. Stable isotope analysis of raccoon muscle samples and the Bayesian mixing model were used to estimate each food resource’s contribution to the raccoon diet. Animal food resources accounted for 70% of total consumed food. The foraging ratios of amphibians and crustaceans were about 9% and 5%, respectively. Raccoons have been found to use amphibians at a higher rate than previously reported, including a rare endangered species, the Hokkaido salamander. Hokkaido salamander and Japanese crayfish spawn in the spring, and increased predation pressure by raccoons may directly impact populations of these rare native species.

Highlights

In Japan, there are concerns that invasive alien raccoons prey on rare native species during their spawning season from late winter to early summer
Identity to reference sequences in the database; these 78,517 reads were assigned to 9 operational taxonomic units (OTUs)
The results suggested that raccoons prey on various animal food resources, including amphibians and crustaceans to the same extent, regardless of the habitat, from late winter to early summer

Summary

Introduction

In Japan, there are concerns that invasive alien raccoons prey on rare native species during their spawning season from late winter to early summer. We analysed raccoon faeces and gastric contents by DNA metabarcoding to detect the rare native Hokkaido salamander and Japanese crayfish. Hokkaido salamander and Japanese crayfish spawn in the spring, and increased predation pressure by raccoons may directly impact populations of these rare native species. Invasive alien species are species whose introduction and/or spread outside their natural habitats threaten biological diversity[1,2]. They are considered one of the most significant causes of extinction and decline of wild native species. Raccoons are omnivorous and known to diversify their diet according to the food resources available in each r egion[4] They are known to prefer aquatic organisms such as amphibians, small fish, and

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Conclusion