Comparative Analysis of the Diets of Pygmy Sperm Whales and Dwarf Sperm Whales in Taiwanese Waters

Abstract

Stomach contents were analyzed of six pygmy sperm whales (Kogia breviceps) and five dwarf sperm whales (Kogia sima) which were taken as by-catch or were stranded specimens in coastal Taiwan from 1998 through 2000. Twenty-two species in 12 families of oceanic cephalopods were identified. In pygmy sperm whales, Enoploteuthis chunii, Sthenoteuthis oualaniensis, and Taonius pavo were the primary prey in the diet, while E. chunii, Histioteuthis miranda, and T. pavo were the most important prey items ingested by dwarf sperm whales. Although the primary prey items these two species ingested were very similar, each item comprised a different proportion for each whale species. A similarity test demonstrated a significant difference in prey composition, and SIMPER analysis showed that E. chunii was ranked first and contributed 37.1 % to the average dissimilarity between pygmy and dwarf sperm whales. Pygmy sperm whales fed on much larger T. pavo compared to those ingested by dwarf sperm whales, while dwarf sperm whales ingested more H. miranda than did pygmy sperm whales. These results support the view that pygmy sperm whales live seaward of the continental shelf and that dwarf sperm whales live more in coastal waters.