Difference in age at first conception between early and late litters of feral raccoon (Procyon lotor) in Kanagawa prefecture

Body Length and Craniometrics of Non-Native Raccoons in Two Regions in Middle Japan during Early Invasion Stages

Although the genetic distribution of introduced raccoons (Procyon lotor) in recent years is well known, few studies have examined their morphometrics, especially the relationships between sex and age in the introduced populations. The aim of this study was to describe the morphological characteristics of raccoons from parts of eastern and western Japan during their early invasion stages, focusing on the relationships between body length and the principal component of craniometrics, with region, sex, age class, body length, and body mass index using a regression model. The body length increased more in males than females and in the older age class, supporting the association with intrasexual selection and competition for food resources. Positive relationships for body length and body mass index were found in craniometric analyses, particularly regarding cranial size components, in addition to age class for both sexes, while cranial size also differed between regions for females. The relationship between body length and craniometrics was inconsistent with that of subspecies originating in North America. Given the sympatric distribution of haplotypes of multiple subspecies without reproductive-isolating barriers in North America and in several introduced areas, hybridization must have occurred prior to the introduction or naturalization of this species.

Body size of raccoons introduced in west-central Hokkaido, Japan: Evaluation using two spatial scales

Evaluating body size as an indicator of life history traits is essential for the proper management of invasive species. The body size of alien species may change due to differing climates at the latitudinal scale and presence of anthropogenic food at a regional scale; however, only few studies have examined spatial variation in body size of alien carnivores at two spatial scales. In this study, we evaluated the body size of adult raccoons (Procyon lotor (Linnaeus, 1758)) inhabiting Hokkaido, Japan by comparing populations from different latitudes. Second, we examined the contribution of anthropogenic food (i.e., residential areas, crop field areas, and livestock farm density) to variations in body size in our study area in west-central Hokkaido. Using body mass as an index of body size, we found that body size did not change along latitudinal clines. Thus, the body mass of omnivorous carnivores may be unaffected by climatic variations. On a regional scale, anthropogenic food did not affect the body mass of raccoons. Thus, anthropogenic food is only supplemental for raccoons in our study area, if at all. We conclude that implementing culling programs are essential for effectively managing invasive species, rather than preventing their consumption of anthropogenic food.