Abstract
We conducted camera trapping surveys on pikas six times over four years in the stunted subalpine forest of Mt. Dairoku (altitude: 1,460 m) in central Hokkaido, Japan. The rhythm of daily activity was analyzed using an exposure time of 167 pika photographs obtained. Pikas were more active during the nighttime than the daytime with one survey excepted. Nocturnal activity was highly conspicuous in autumn. Annual and seasonal differences in activity could not be accounted for by the suppression effect of high air temperature. We did not observe the previously reported bimodal pattern of activity with peaks at dawn and dusk. Studies of Ochotona species, including the northern pika, seem to have been conducted on the assumption that they are primarily active during the daytime. However, this assumption needs to be reexamined.
