- A six-year project has for the first time recorded the vocalisation made by sperm whales in the Antarctic.
- Slow clicks are thought to be linked to communication.
- The steady beat of what the scientists call usual clicks are linked with echo-location and foraging.
Sperm whales, those toothed whales with the biggest brains on earth, are noisy animals.
They make sounds, a stream of clicks and burrs, about 80% of the time when they are diving, according to Australian researchers.
Scientists using underwater listening devices have made the first long-term recordings of sperm whale calls off East Antarctica as the marine mammals hunt their prey, which includes giant squid.
“This is the first study to directly measure the seasonal presence and daily behaviour of sperm whales in Antarctica,” says Dr Brian Miller, an acoustician with the Australian Antarctic Division.
“The recordings show that adult male sperm whales forage in Antarctic waters in summer and autumn, and depart the region once heavy sea ice sets in over winter.
“We also found the whales predominantly foraged during daylight hours and were silent at night, possibly due to the availability of their prey.”
Dr Miller and consulting ecologist Dr Elanor Miller used custom-designed and built acoustic moorings to record sperm whale sounds over six years.
The scientists discuss their findings:
They recorded thousands of hours of loud “usual clicks”, which have a regular beat that the whales use to echo-locate prey such as fish and squid.
The researchers developed a computer algorithm to trawl through more than 46,000 hours of underwater sound recorded at three sites off East Antarctica, to identify the distinctive sperm whale clicks.
“Sperm whales have four types of vocalisations — slow clicks, usual clicks, creaks and codas,” Dr Brian Miller said.
“Slow clicks and codas are thought to be linked to communication, while usual clicks and creaks are linked with echolocation and foraging.
“Usual clicks are produced about 80% of the time the whales are underwater, which makes the whales ideal subjects for acoustic monitoring.”
The regular beat of a sperm whale’s varies but is usually ranges from about twice per second to once every two seconds.
Scientist say their ability to glean information from the underwater recording devices will improve as the technology continues to develop.
“These studies are an important stepping stone for measuring the number of sperm whales using Antarctic waters,” says Dr Miller.
“Sperm whales are a key predator in the Southern Ocean ecosystem and this work will inform environmental management decisions for this vulnerable species.”
The research was published in the journal Scientific Reports.
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