Diet Composition of the Gray Whales ( Eschrichtius robustus ) Depending on Sex and Size, Using Specimens From Mechigmen Bay (Bering Sea)

Abstract

The Mechigmen Bay of the Bering Sea is one of the feeding areas used in summer by the Chukotka‐California population of gray whales ( Eschrichtius robustus ). This study focuses on the analysis of stomach contents of juvenile gray whales harvested by local peoples of Chukotka in autumn 2024, along with an assessment of the relationship between diet composition, sex, and body size of the specimens. A total of 39 taxa of benthic invertebrates were identified in the whales' stomachs, with the highest diversity recorded among the orders Amphipoda (24 species) and Cumacea (eight species). Based on the taxonomic composition and ecological characteristics of the prey items, hypotheses were proposed regarding the whales' feeding strategies and the spatial distribution of their main foraging areas within the bay. The number of species and diversity of prey were similar in the stomach contents across whales of different body sizes and sexes. The composition of dominant macrotaxa in the diet was also similar between males and females. However, a significant trend was observed toward more frequent consumption of ascidians attached to rocky substrates by larger individuals of gray whales. This finding suggests potential physiological and behavioral differences between size groups of the species.

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