Occurrence, site‐fidelity and photo‐identification of long‐finned pilot whales in Aotearoa New Zealand

Abstract

Despite frequently stranding, little is known about free‐ranging long‐finned pilot whales ( Globicephala melas edwardii ) in Aotearoa/New Zealand. This study used long‐term data to determine the occurrence, seasonal site‐fidelity, group size distribution and individual identity of pilot whales off the east coast of New Zealand. Photographs ( n = 53,857) and sightings metadata from 81 pilot whale groups were collected opportunistically from research vessels and whale watch tour operators from the Bay of Islands to Kaikōura between 2003 and 2019. A total of 2144 good‐quality photographs from 41 encounters were used to identify 145 distinctive individuals using dorsal fin markings. The mark rate (13.4%) was low compared to northern hemisphere pilot whales. While the overall (31%) and between‐year resight rates (13.8%) were low, results suggested some degree of site fidelity and supported the peak in occurrence over summer, as reported from stranding records. Pilot whales were mainly found in mixed‐species groups, demonstrating inter‐specific associations (79%, n = 64). Opportunistic datasets were valuable for understanding occurrence and site‐fidelity of a poorly‐studied species in the southern hemisphere. Future photographs and sightings records will support a more complete understanding of pilot whale distribution and enable a broader‐scale assessment of demographic patterns and social structure of this species.

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