2017 Volume 57 Issue 2 Pages 235-239
A camera trapping survey in the northern part of Okinawa Island suggests that the Okinawa spiny rat Tokudaia muenninki (Rodentia, Muridae) changes its daily activity cycle throughout the year, being diurnal in summer and nocturnal in winter. In the summer study period (late June to late September), the Okinawa spiny rat was photographed only in daytime (n = 12, 10-day average of daily mean air temperature = 23.5–26.9°C), while in the winter study period (early January to late March) the rat was photographed only at night (n = 13, 10-day average of daily mean air temperature = 13.8–17.5°C). On the other hand, the sympatric invasive black rat Rattus rattus was photographed at night in both seasons (n = 15 in summer and n = 6 in winter), suggesting that the activity patterns of the two rat species overlapped only in winter. Little is known about the biology of the Okinawa spiny rat, and our study is the first report of such unique behavior of its daily activity changes. More studies are needed to understand the significance of the behavior and to reveal its influence on the recent population decline of the species.
