To understand the present status of spotted seals (Phoca largha) at Lake Furen in eastern Hokkaido, Japan, we investigated seasonal variations in the number from May to the month before the sea-ice season between 2012 and 2016.
There were no differences in the seasonal variations of total spotted seal numbers at Lake Furen from 2012 to 2016, and the number of hauled-out seals alone increased until September and decreased from October. Since this trend in the numbers of hauled-out spotted seals at Lake Furen is the same at other summer habitats that have been reported, the haul-out periods of spotted seals are consistent at their various summer habitats. At Lake Furen, the number of hauled-out spotted seals and the tide have a strong relationship in analyses using generalized linear models; hauled-out seals were observed only when the tide was below 80 cm, but few were observed above that level. This study has also found that the tendency for numbers from October to increase above summer numbers indicates that there are more individuals that migrate as far south to Lake Furen in autumn prior to the arrival of sea-ice.
