Dataset for density estimation for an island population of raccoon dogs in Japan

Estimation of the population size is essential for understanding
population dynamics. Estimating animal density using multiple methods
and/or multiple attempts is required for accurate estimations. Raccoon dog
(Nyctereutes procyonoides) is native to East Asia, including Japan, and
has become an invasive species in Europe. Information on raccoon dog
density in their native range is important to understand their invasion;
however, relatively few studies have been conducted on raccoon dog density
in their native range. In this study, we extracted DNA from fecal samples
of raccoon dogs inhabiting a small island in Japan and conducted density
estimation over two periods using DNA capture-recapture methods: CAPWIRE
and SECR. We also investigated sex ratio using genetic sex identification.
Density estimates using SECR were approximately threefold different
between the two study periods: 17.2 individuals per km2 in 2018 and 49.0
individuals per km2 in 2020. In contrast, estimates using CAPWIRE
were relatively stable: 21.7 individuals per km2 in 2018 and 24.3
individuals per km2 in 2020. A drastic increase or decrease is
not expected during the study period, and thus, density estimates using
CAPWIRE are more reasonable than those using SECR. The small number of
samples per individual might result in low accuracy of density estimates
by SECR. The density estimated by CAPWIRE was similar to that in the main
island in Japan and higher than that in Europe. Feeding competition with
other omnivorous carnivores and/or predation risk by wolves might maintain
the low density in Europe. The sex ratio of raccoon dogs was 1:1, which
was similar to the values in invasive raccoon dogs and other canids.
Further genetic census, including sex identification in various landscapes
in their native and invasive range, will enable us to understand not only
the ecology of raccoon dogs but also their adaptations to their invading
areas.