Related BBC sites

Page last updated at 22:14 GMT, Monday, 14 March 2011
Beaked whales 'scared' by navy sonar
By Ella Davies
Earth News reporter

Beaked whale's head (c) Diane Claridge / Bahamas Marine Mammal Research Organisation

Beaked whales are disturbed by naval sonar, according to scientists.

A new study suggests that the whales are particularly sensitive to unusual sounds.

Measuring their reactions to both simulated sonar calls and during actual naval exercises, researchers found the whales fell silent and moved away from the loud noises.

The use of sonar for naval communication has been linked to beaked whales stranding in the past.

Scientists from the University of St Andrews, Scotland have been working with marine experts from around the world to investigate how sonar affects beaked whales in the Bahamas.

We showed that the animals reacted to the sonar sound at much lower levels than had previously been assumed to be the case
Professor Ian Boyd

Beaked whales are an elusive group of small whales named for their elongated snouts.

However, they are probably best known for their connection to the possible risks that naval sonar poses to marine mammals.

For example, in 2000 and 2002, large groups of beaked whales stranded and died.

Naval exercises involving sonar communication were taking place nearby on both occasions, raising concerns that the whales' deaths were directly linked to the mid-frequency signals.

In their study, published in the journal PLoS One, researchers focussed on waters around the US Navy's Atlantic Undersea Test and Evaluation Center.

Blainville's beaked whales (Mesoplodon densirostris) have been identified foraging in the area by the navy's acoustic monitoring equipment, used for listening to signals from submarines.

The scientists listened to the group of whales using these hydrophones - underwater microphones.

During live sonar exercises by the US Navy, the whales stopped making their clicking and buzzing calls, which they are thought to use to navigate and communicate.

"Results... indicate that the animals prematurely stop vocalisations during a deep foraging dive when exposed to sonar. They then ascend slowly and move away from the source, but they do resume foraging dives once they are farther away," said David Moretti, Principal Investigator for the US Navy.

Using tags attached to the whales, the team was also able to track their movements with satellites.

They found that the whales moved up to 16km away from the area during sonar tests and did not return for three days.

Beaked whale breaches (c) Charlotte Dunn / Bahamas Marine Mammal Research Organisation

"It was clear that these whales moved quickly out of the way of the [navy] sonars. We now think that, in some unusual circumstances, they are just unable to get out of the way and this ends up with the animals stranding and dying," said Professor Ian Boyd, chief scientist on the research project.

To further understand the whales' behaviour, the team also played simulated sonar calls to the whales, including the calls of killer whales.

The beaked whales showed the same avoidance behaviour in response to these calls.

"It appears that they just don't like unusual sounds. But the way in which sonars are used to hunt for submarines may mean that the whales are more vulnerable to that type of sound," said Prof Boyd.

SONAR
Sonar stands for SOund Navigation And Ranging
In their tests, the US navy used active sonar - emitting pulses of sound and using the echoes to calculate the location of other vessels
Animals such as bats and dolphins use echolocation in the same way to navigate their surroundings

They are known to emit high-frequency calls but this is the first time anyone has proven that they react to mid-frequency sounds.

"We showed that the animals reacted to the sonar sound at much lower levels than had previously been assumed to be the case," said Prof Boyd.

"Perhaps the most significant result from our experiments is the extreme sensitivity of these animals to disturbance."



Print Sponsor


SEE ALSO IN EARTH NEWS
How orcas hunt in 'stealth mode'
03 Mar 11 |  Earth News
Whale strandings 'increase 25%'
25 Nov 10 |  Northern Ireland
Rare whale gathering sighted
04 Nov 09 |  Earth News
Beaked whales: Your questions answered
03 Oct 08 |  Science & Environment
Beaked whales: Sounding off
30 Sep 08 |  Science & Environment
Beaked whales - into the abyss
29 Sep 08 |  Science & Environment
Sonar 'may cause whale deaths'
08 Oct 03 |  Science & Environment

OTHER RELATED BBC LINKS

MOST POPULAR STORIES

From Science/Environment in the past week

  • TUESDAY :
  • MONDAY :
  • SUNDAY :

BBC navigation

BBC © 2013 The BBC is not responsible for the content of external sites. Read more.

This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.

Americas Africa Europe Middle East South Asia Asia Pacific