Sperm whale mysteries unlocked by recordings

CUTTING-EDGE audio technology is helping scientists shine a light on the mysterious world of sperm whales in Antarctica.

Australian Antarctic Division acoustician Brian Miller and consulting ecologist Elanor Miller are using custom-designed acoustic moorings to record whale vocals.

More than 46,000 hours of underwater audio has been recorded over the past six years in a bid to hear the distinctive sounds of sperm whales.

The scientists have discovered thousands of hours of loud clicks, which have a regular beat that the whales use to echo-locate prey such as fish and squid.

It is the first study to directly measure the seasonal presence and daily behaviour of sperm whales in Antarctica, and the first time long-term sperm whale calls have been recorded off East Antarctica.

“We’ve been able to get the most detailed view of the behaviour of sperm whales in the Antarctic to date,” Dr Miller said.

A computer algorithm was developed to determine automatically when sperm whales were present in the recordings.

“We were able to find that sperm whales were present in the Antarctic in the summer and autumn months, and that they were absent in the winter and spring months when there was heavy ice cover,” Dr Miller said.

“On top of that we were able to listen to the daily behaviour of sperm whales, and we were able to determine that they were much more likely to be detected during daylight hours than at night time.

“Many different animals in the Antarctic are known to have daily cycles, and this behaviour of the sperm whales suggests that they’re capitalising on the daily cycles of their prey.”

Electronics design engineer Mark Milnes said the “cutting edge” acoustic moorings recorded to SD cards, and were developed at the AAD specifically to do long-term recordings of marine mammals.

“That’s a real point of difference to what other institutions have done in terms of recording marine mammals where they’ve had to record for 10 minutes and then turn off for half an hour or so,” Mr Milnes said.

The moorings can withstand 0C water temperatures at depths of up to 3500m while continuously recording.

shaun.mcmanus@news.com.au