Description and analysis of cephalopod beaks from stomachs of six species of odontocete cetaceans stranded on Hawaiian shores

Cephalopod prey of several cetacean species from Hawaiian waters were identified and quantified from the beaks in stomachs of stranded individuals. The different species of cetaceans all appear to target different species and sizes of cephalopods. Beaks from two sperm whales (Physeter catodon) included a total of 312 upper and 292 lower beaks (mandibles) of cephalopods. All of the cephalopods represented by lower beaks were oceanic squid belonging to 20 or more species in 14 families. The major constituents of the whale diet were Histioteuthis hoylei (45% by number and 109% by dry weight), Ommastrephes bartrami (7.6% by number, 30.6% by weight) and Architeuthis sp. (only 0.7% by number, but 26.5% by weight). in a Risso's dolphin (Grampus griseus) stomach, 1051 upper beaks and 1349 lower beaks were present. Eighteen or more genera of cephalopods in 15 families were present. The major constituents of the Grampus diet were Enoploteuthis spp. (36.1% by number and 30.1% by dry weight) and Abraliopsis spp. (23.6% by number, but only 4.9% by weight) and O. bartrami (1.3% and 32.1% respectively). The melon-headed whale (Peponocephala electra) eats fish as well as cephalopods which are represented by only six lower beaks belonging to five genera, Enoploteuthis, Teuthowenia, Abraliopsis, Abralia sp. and Bathyteuthis abyssicola. The beaked whale (unidentified) contained two lower beaks which were O. bartrami. Stenella attentuata also eats fish and the sample contained lower beaks, one of Enoploteuthis sp. and seven of an Abraliopsis sp. Stenella longirostris mainly contained 64 lower beaks, 61 of which were Abralia trigonura.