Antarctic blue whale song penetrates the vast Southern Ocean
Antarctic marine scientists eavesdropping on the world’s largest creature, the blue whale, have detected individuals singing from almost 750 kilometres away.
The researchers, part of a six week Australia-New Zealand Antarctic Ecosystem Voyage to the Southern Ocean investigating the region’s top predators, returned to Wellington, New Zealand today.
Australian Antarctic Division Lead acoustician, Dr Brian Miller, said directional sonobuoys were used to listen for the low rumbling song of blue whales and guide the ship to them.
“It is really exciting to be able to study these whales in the vast Southern Ocean and hear their calls over 750kms away,” Dr Miller said.
“During the voyage we were able to record more than 40,000 calls over 520 hours.”
Australian Antarctic Division Voyage Science Leader, Dr Mike Double, said after travelling a large distance without sighting any whales, they were staggered to witness over 80 of these rare whales in a relatively small area.
“With such a patchy distribution it is only possible to study this endangered species efficiently using the acoustic technology developed by the Australian Antarctic Division”.
The scientists photo-identified 58 individual blue whales during the voyage. These images will help estimate the population size, rate of recovery and movements of the endangered Antarctic blue whales.
“Our ability to find these whales and the multidisciplinary nature of the voyage also allowed us to investigate the whales’ habitat.”
"Using echosounders we were able to map, characterise and monitor the krill in the vicinity of the blue whale and found the swarms were denser than those found anywhere else.
“Remarkably, using new advanced echosounders, we were able to track individual krill for the first time allowing an examination of the changing internal structure of the krill swarms.
“Additionally oceanographic data was gathered which will show the productivity of the waters.”
The voyage is a collaboration between Antarctica New Zealand, the New Zealand National Institute of Water and Atmospheric Research (NIWA) and the Australian Antarctic Division.
The non-lethal whale research conducted on this voyage aimed to investigate key questions identified by the International Whaling Commission’s Southern Ocean Research Partnership (SORP).
The Australia-New Zealand Antarctic Ecosystems Voyage 2015 accomplished all science objectives they set out to achieve.
Some summary facts and figures from the voyage include:
- Nearly 15,000 km travelled.
- Over 520 hours of whale song recordings with more than 40,000 individual calls detected.
- Photo-identification of 58 individual blue whales (including re-sightings).
- Biopsy samples from 11 humpback and blue whales.
- 40 trawls (18 demersal tows and 22 midwater tows).
- 111 species or species groups caught.
- 3,129 fish and krill individually measured.
- 370 biological sample lots retained for further analysis.
- 345 gigabytes of echosounder acoustic data recorded.
- Nearly 1,000 hours of continuous underway oceanographic and atmospheric data collection.
- Over 3,500 litres of seawater filtered.
- 33 on-board experiments to measure primary production.
- 55 underway conductivity-temperature-depth (CTD) profiles.
- Twelve Argo oceanographic floats deployed.
- Ten deployments of a continuous plankton recorder (CPR).
- 200 days recording time for moored echosounder monitoring silverfish migration in Terra Nova Bay over winter.
- Eight scientific echosounders calibrated.
- Listen to the blue whale call
- Scientists return from successful Antarctic research voyage – joint NIWA-AAD press release
- AAD Voyage homepage
Antarctic blue whale voyage returns
Low frequency whale sounds
Australian Antarctic Division Voyage Science Leader, Dr Mike Double:
Occasionally you sit back and go "how loud is that?", you know? It’s just incredible to think that these sounds from individual whales are travelling so far.
We covered about 15 000 kilometres on this voyage. We were deploying sonobuoys throughout, so these are the devices that listen to the low frequency sounds that blue whales produced. I think our longest detection was over 1000 kilometres, so we were hearing them at Terra Nova Bay and we were about 750 kilometres from the aggregation that we'd left. So we knew that we were detecting from 750 kilometres, but really on the way back we were still hearing that aggregation over a thousand kilometres away. We just have to pinch ourselves and remind ourselves that, you know, this is some of the loudest sounds that we hear in nature.
We actually encountered two blue whales at the Balleny Islands, but then we were hearing a lot of whales to our south-east, and when we got into that area we realised we'd found a lot of blue whales in a very small area. So in about 100 kilometres by 100 kilometres there was probably in the region of about 80 to 100 blue whales.
We could work with the whales, we could approach them, we could follow their behaviours doing video-tracking work. We took a biopsy sample.
During the day we were working with the blue whales, at night we were running krill surveys. We found some really interesting data on the krill themselves. We actually found there weren't actually… there was a lot of whales, but not a lot of krill dispersed, but when we found the krill they were in very very tight swarms. So now we're trying to understand, you know, why this habitat is particularly attractive to the blue whales.
I mean I was really surprised to see so many blue whales in such a small area. I mean, when you’re on the ship and you're on the bridge and you’ve got almost 360 degree views and you're seeing these huge blows around, around, all around the vessel, you know that was really surprising. You’re dealing with a rare endangered species and yet you’re surrounded, and like Richard said, we're becoming blasé about seeing Antarctic blue whales.