Scientists trial first multimedia whale trap in the Ross Sea

A research team from the University of Canterbury has just returned from an Antarctic expedition to find out more about the secret lives of whales, specifically Type-C killer whales.

Type-C killer whales, or ‘Charleys’ after the phonetic alphabet, are distinctive Antarctic dwarf killer whales that hunt fish, including toothfish. As toothfish predators, Charleys are a focal species for the new Ross Sea region Marine Protected Area (MPA) and act as sentinels for the effectiveness of marine protection created by the MPA.

Unlike many marine mammals, Charleys are right at home in dense pack ice that keeps out other types of killer whales, says team leader Dr Regina Eisert, from UC’s Gateway Antarctica. During the Antarctic summer, Charleys follow the receding ice edge south and can be seen breathing and ‘spyhopping’ in narrow leads in the ice.

Every January, an icebreaker prepares a channel in the sea ice covering McMurdo Sound to allow the re-supply of McMurdo Station and Scott Base. As soon as the channel is ready, Charleys move in, and this ‘whale highway’ in turn creates unique opportunities for scientists.

“Using mostly New Zealand-made instrumentation, we installed several arrays containing cameras and hydrophones along the channel to monitor the whales’ movements, and record their images along with their vocalisations,” says Dr Eisert.

“At first, we were a bit concerned that we would not be able to detect the whales in the channel, but as soon as we installed the first array, we had visitors. The Charleys were intensely curious about what we were doing and came to check us out.”

Over the next few days, inquisitive whales surfaced near the arrays and had their picture taken, while hydrophones recorded their vocalisations.

Joint analysis of images and underwater sounds by UC PhD student Alexa Hasselman, who has spent the summer researching on the ice, supervised by UC Engineering Associate Professor Michael Hayes and UC marine scientist Andrew Wright (now at Bedford Institute of Oceanography), will enable calls to be assigned to groups and individual whales, as well as reveal diel patterns in the whales’ movements. The research also lays the groundwork for larger-scale acoustic monitoring of killer whales and other whales in the Ross Sea region, an important milestone for the Ross Sea region MPA.

Dr Eisert says she is grateful for the support of the Pew Charitable Trusts, Antarctica New Zealand, the United Nations Environment Program, the Ministry of Primary Industries, and Canon NZ Ltd.

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