Seasonal feeding on giant cuttlefish (Sepia apama) by Indo-Pacific bottlenose dolphins (Tursiops aduncus) in south-western Australia

Abstract

We report on observations of Indo-Pacific bottlenose dolphins (Tursiops aduncus) feeding on giant cuttlefish (Sepia apama) from March 2007 to April 2013 in the temperate waters off Bunbury, south-western Australia. Seventeen feeding events were observed during the cooler months between July and September in relatively shallow coastal waters, with 12 dolphins identified as adult females. We observed behavioural sequences of complex prey-handling of cuttlefish where dolphins’ used multiple steps to remove the cuttlefish head, ink and cuttlebone before consuming the flesh of the cuttlefish mantle. Our study provides valuable information to the limited knowledge on the complex prey-handling by T. aduncus on cuttlefish in Australia, and is complementary to other known specialised foraging behaviours of bottlenose dolphins. This study also details a different behavioural sequence of cuttlefish prey-handling to that of the bottlenose dolphins in the Sado estuary, Portugal, where only the head is consumed, and to the Spencer Gulf, Australia, in that the dolphins in Bunbury carry the cuttlefish mantle over their rostrum before removing the cuttlebone. Information on S. apama in Bunbury is scarce, therefore studies on abundance, distribution and egg-laying sites are recommended in order to enable informed decision making and to understand the importance of S. apama to the diet of T. aduncus.