The discovery of a breeding population of Japanese pond turtles at the northern limit of the Pacific Ocean side of Japan

抄録

The Japanese pond turtle (Mauremys japonica) is endemic to Japan, inhabiting Honshu, Shikoku, Kyushu, and smaller islands. The ecology and distribution of M. japonica have been well studied in western Japan. In contrast, much less studies of this species have been performed in the Kanto and Hokuriku regions and its northern limit is not clear. Here, we report the discovery of a local population of M. japonica in a river in the Ibaraki Prefecture, representing the northern limit of its range on the Pacific Ocean side of Japan. This investigation revealed the inhabitation of over 50 turtles aged 0–10 years in the river. The predicted growth curves of both male and female turtles were comparable to those in other river and wetland populations previously reported, indicating that this population reproducing and growing normally. We also discuss future conservation strategies for this population.