Shipping noise causes major ‘stress’ in whales

“To our knowledge, there were no other factors affecting the population that could explain this difference besides the decrease in ship traffic,” stated Dr Rosalind Rolland, who led the study.

“We showed whales occupying oceans with high levels of ship noise have a chronic stress response.

“We knew whales changed the frequency of their calls to adapt to the ship noise, but this work shows it is not merely an annoyance – it is having a physical effect.”

Ships’ propellers emit sound in the same frequency range that some whales use for communicating. Previous studies have shown the whales change their calling patterns in noisy places.

The effect on whales of propeller noise, military sonar and explosions during oil and gas exploration is highly controversial. Environmental campaigners claim the noise interferes with the singing of whales and can even kill the animals.

Over the past 50 years noise caused by cargo and military vessels, along with high-decibel sonars used for oil exploration, has gradually increased in intensity and scope.

The International Maritime Organisation and the European Union are both investigating how to reduce marine noise.

Baleen whales communicate at the same low-frequency wavelengths emitted by these ships, in the range of 20 to 200 hertz (Hz), and some species have adapted by emitting louder and more frequent acoustic signals.

Just weeks before the terrorist attacks, the scientists started investigating the North Atlantic right whales, which travel up and down the North American east coast, before congregating in late summer in Canada’s Bay of Fundy to feed and nurse their calves.

Starting in July 2001, the researchers used trained dogs to find whale faecal matter floating on the surface of the water. They collected samples over a six-week period every year through 2005.

It contained hormone-related chemicals, called glucocorticoids, mirroring stress levels that could change from one day to the next, or even within hours.

When the researchers noticed the drop in underwater noise levels, they realised it would be an opportunity to investigate whether sound pollution was a cause of stress for right whales.

They found that changes in the concentration of the hormone matched perfectly the sudden drop and gradual renewal of maritime traffic in the area.

“The positive aspect to this particular issue is that it is a solvable problem,” stated Dr Rolland.

Glucocorticoids are secreted in a crisis: aggression by a predator or competitor, starvation, drought. In the short run, this rush of hormones helps animals cope by summoning reserves of energy.

But over the long haul, constant elevations of the hormone due to stressful situations becomes a detriment, leading to stunted growth, a weakened immune system and a compromised capability to reproduce.

Studies of land animals have shown that this kind of chronic stress can be caused by noise from snowmobiles, along with tourism or road traffic.

A separate study published in January showed the singing of humpback whales was disrupted by sonar noise caused nearly 200 miles away.

Because they live, feed and breed so close to shore, critically endangered North Atlantic whales are already threatened by ship collisions and fishing gear entanglements, two leading causes of death among massive cetaceans.

The team did not study the effect of noise on the animals.

More source:

Shipping noise causes major 'stress' in whales - Telegraph
PressTV - Shipping noise causes major stress on whales
Study Shows Commercial Shipping Noise Causes Physical Stress to ...
Shipping causes 'chronic stress' to whales | Environment | The ...

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Submited at Wednesday, February 8th, 2012 at 7:00 am on Uncategorized by luci
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