Abstract
Since the 1980s, the number of kuril harbour seals (Phoca vitulina stejnegeri) hauled out in eastern Hokkaido has been believed to be low from autumn to winter; this number increases through the breeding season in May and June and then peaks in the molting season in July and August. However, yearlong investigations have revealed that this pattern does not apply to Hamanaka A (a haul-out site at Hamanaka, eastern Hokkaido). The number of kuril harbour seals at Hamanaka A varies with season. It is low in the breeding season; increases through the molting season and autumn, i.e., September through November; decreases in winter, i.e., December through February; and increases in the pre-breeding season in March and April. These variations in the number of kuril harbor seals hauled out at Hamanaka A differed from those previously reported.
