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Whales Sounds Award for Cato

4 December 2012
Dr Doug Cato is the winner of the 2012 Minister's Achievement Award in Defence Science for his work on whales sounds
Dr Doug Cato is the winner of the 2012 Minister's Achievement Award in Defence Science.

The 2012 winner of a prestigious award in defence science began his scientific career as a geophysicist, but exploring the sounds of a world once thought silent has proved to be his true calling.

Doug Cato is now the chief scientist of the Behavioural Response of the Australian Humpback whales to Seismic Surveys Program – and still very much a defence scientist.

And that contribution was recognised by Minister for Defence Science and Personnel Warren Snowdon in awarding him the Minister's Achievement Award in Defence Science for 2012.

After joining the Royal Australian Navy Research Laboratory as an oceanographer, on the basis of a single lecture experience, Doug quickly moved into acoustics, the hot topic at the time in defence maritime science.

His first area of research was as part of a team trying to acoustically detect submarines off the coast of Australia. They learned there was a great deal of variation in the ability to detect submarines, depending on environmental conditions such as the background noise and how the sound travelled through water. Water properties, like temperature variation with depth and the sea floor, impact on how sound travels through water. Sounds from submarines have to be detected against the variable background ambient noise.

Whales Sounds

Doug’s early work was to draw up a series of curves which allowed sonar operators to predict the performance of their equipment based on the likely ambient noise of the environment the submarines were operating in.

“Sonar detection ranges can vary, by a factor of ten quite commonly, it could happen in half an hour,” he said.

“If sonar operators and submarine commanders don’t know how the sonar conditions are varying, their submarines are very vulnerable. In bad conditions, sonar operators might wonder why their sonar doesn’t seem to work now, but if you can forecast sonar performance, you can plan for it. So that drove a lot of my work."

“Then I started to get questions from sonar operators and submariners about strange sounds they were hearing. If submariners hear a strange sound it’s something they’re really concerned about – they wonder what’s out there."

“I thought these were probably whales. I had recordings of whales sounds from American laboratories, so I had an idea of what they sound like, but I had to find out what our whales sounded like. To do that I had to find someone who knew where the whales were.”

Commercial whaling in Australia ended in 1978 and, after a few years, there was evidence that whale numbers were increasing. It’s likely that before the population began to grow there were so few whales that it would have been rare to hear their sounds.

When sonar was first thought to be a wonderful tool to pick up submarines, no-one imagined that all the other sounds of the ocean, from fish and other sea creatures, would make it difficult to hear submarines.

“It turns out fish make a lot of noise too,” Doug said.

“You have choruses where the whole background noise rises by 20 decibels – it’s like the cicadas in the trees.  Many fish have swim bladders that they can drum or strum, it’s a very efficient source of sound. And shrimps make a lot of noise.”

"...this is the leading edge of behavioural studies now."

To study whales sounds and fish sounds to discover their effects on sonar, Doug worked with biologists who knew their distributions and behaviour. 

When concern arose that sonar and other man-made underwater noise could have an effect on whales, Doug was already working on whale acoustics and could see it becoming a serious problem. And the Royal Australian Navy took it seriously, too.

The Behavioural Response of Australian Humpback whales to Seismic Surveys program is the largest project in the world on the effects of noise on whale behaviour.

The program involves DSTO, the University of Sydney, University of Newcastle, University of Queensland, Curtin University and the Australian Marine Mammal Centre (part of the Antarctic Division), and  a range of experts in underwater acoustics and marine biology.

“It’s funded by an international research funding agency supported by the oil and gas industry and partly by the US Government regulators,” Doug said.

“So this is the leading edge of behavioural studies now.”

The project uses theodolites to track whales every time they come to the surface to breathe, and their other activities at the surface. The movements of vocalising whales are tracked with an acoustic array. Some whales are tagged for a few hours so that a more three-dimensional view of their underwater behaviour can be obtained. The project is focusing on the behaviour of Australian humpback whales which are among the most studied in the world, so a lot is known about their normal behaviour.

Behaviour of groups of whales are observed for an hour before they are exposed to the sound source. Then the sound source operates for an hour and then another hour of observation follows after the source has stopped. A full series of control studies in which there is no noise exposure is also undertaken. 

Whales normally show a lot of different behaviours as well as swimming and it’s not easy to determine if the behaviour you see in response to noise is significantly different to the behaviour they would have shown anyway. 

“The reaction to sounds is variable, it depends on many other factors, for example on whether it’s mothers and calves or lone males, how close the source is et cetera,” Dr Cato said.

For noisy activities at sea, such as seismic surveys and naval exercises, the impact of noise is managed by having an exclusion zone around the noise source. Observers look out for marine mammals and the activity does not start if they are within the exclusion zone. If whales come within the exclusion zone during the operation, the noise source is shut down. Exclusion zones are based on limited information and there is concern about whether they are the most effective measures.

Understanding whale behaviour is crucial, and to do this a very large sample of observations, measurement and recording is required to ensure that observed effects can be attributed to the causes that lead to them.  Seventy people were involved in the last experiment.

“Behavioural responses can occur at large distances,” Doug said.

“If a whale hears a sound, there is the potential for it to react, so it’s very hard to regulate – to say well, as long as you keep sound levels below this amount it will be OK. We’ve found that they’ll react at levels which are right down near the background noise when exposed to tonal sounds. But what we’re really concerned about, and this is what the regulators are concerned about, is what reactions are going to have longer-term biological effects. If they just veer away a little bit and then go back to what they were doing, that doesn’t have longer-term consequences."

“But if it’s something that causes animals to, say, move away from where they normally feed, that might have a longer-term effect. So we need to understand how the reactions to noise compare with normal behaviour and work out the longer term effects, and these require a lot of knowledge about whale behaviour and biology.”