Feeding pattern change of spotted seals (<i>Phoca largha</i>) newly weaned pups on the coast of Hokkaido, Japan

DOI
  • Takano Nobumichi
    Graduate school of Bioindustry Science, Tokyo University of Agriculture
  • Kobayashi Mari
    Laboratory of marine biology, Department of marine fisheries science, Faculty of Bioindustry, Tokyo University of Agriculture

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  • 北海道北部およびオホーツク海沿岸におけるゴマフアザラシ（<i>Phoca largha</i>）の離乳直後の食性型の変化

Abstract

<p>Young and adult individuals of spotted seals (Phoca largha) migrate to the coast of Hokkaido, Japan. Here, their diet includes euryphagous, and they mainly feed on fish and cephalopods in shallow coastal waters. The newly weaned pups utilize small planktonic crustaceans, including krill, as prey in addition to fish prey. In this study, we aimed to analyze the dietary changes of newly weaned pups in the coastal waters of Hokkaido, Japan to understand the specific aspects and timing of these changes. Ordinal logistic regression showed that the krill-specific diet was mainly observed in March; the combined diet, which consisted mainly of krill and fish, was observed in April; and the fish-specific diet, which consisted mainly of fish, was observed in May. The newly weaned pups that lacked experience in foraging and swimming ability actively used krill as their main prey. Later, with the disappearance of sea ice, they shifted to a fish-specific diet, suggesting that the active use of bottom-layer fish is an advantageous strategy for their survival.</p>

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