Feeds

Sonar causes (temporary) deafness in dolphins

One unlucky bottlenose

Build a business case: developing custom apps

Exposure to military sonar may cause temporary hearing loss in bottlenose dolphins, scientists at the Hawaii Institute of Marine Biology have found.

Tests on a captive dolphin indicate exposure to sonar at high, prolonged levels can cause temporary deafness for as long as 20 to 40 minutes — but only if the dolphin stays close to the source of the sonar for several minutes.

In the past decade, numerous beachings of whales, dolphins, and porpoises have been blamed on navies pinging sound pulses into the oceans and listening for the echoes to detect enemy submarines and mines. In particular, mid-frequency active sonar has been fingered as injuring marine mammals and causing some to run aground.

A paper published in the Brit journal Biology Letters today, scientists have reported the first controlled study on the effects of sonar in dolphins.

One very lucky dolphin in an open-water pen was fitted with suction cup sensors to monitor its brainwaves as it was made to listen to recordings of real naval mid-frequency sonar played progressively louder.

When the pings reached 214 decibels underwater* and were repeated, the data showed the dolphin had become temporarily deaf. Other sensors showed the dolphin's breathing rose significantly when the sonar was switched on.

Hearing was typically restored after 20 minutes, but sometimes took as long as 40 minutes. Aran Mooney of the University of Hawaii said the deafening results are akin to a "rock-concert effect" for the mammal because the real-world equivalent of the results would require a dolphin to be just 40 meters from the source of the sonar and remain there for about 2.5 minutes. That's an unlikely scenario for a wild animal, the paper reports, unless there's some unusual conditions involved. For example, sound traps like underwater caverns on the sea bed or a layer of warm water at the oceans surface could cause sonar to bounce around a smaller area.

This could explain why dolphin beachings are relatively rare compared to how often mid-frequency sonar is used in military exercises.

The paper notes additional studies are needed to see how the sonar affects wild animals that aren't used to noise experiments. ®

*203dB above the water would instantly ruin your hearing at best. Under water, it's roughly the equivalent of 170dB in the air (like a gunshot 1 meter away — but that's still loud as hell).

Securing Web Applications Made Simple and Scalable

More from The Register

next story
SMELL YOU LATER, LOSERS – Dumbo tells rats, dogs... humans
Junk in the trunk? That's what people have
The Sun took a day off last week and made NO sunspots
Someone needs to get that lazy star cooking again before things get cold around here
Boffins discuss AI space program at hush-hush IARPA confab
IBM, MIT, plenty of others invited to fill Uncle Sam's spy toolchest, but where's Google?
Famous 'Dish' radio telescope to be emptied in budget crisis: CSIRO
Radio astronomy suffering to protect Square Kilometre Array
BEST BATTERY EVER: All lithium, all the time, plus a dash of carbon nano-stuff
We have found the Holy Grail (of batteries) - boffins
ASTEROID'S SHOCK DINO-KILLING SPREE just bad luck - boffins
Sauricide WASN'T inevitable, reckon scientists
Bad back? Show some spine and stop popping paracetamol
Study finds common pain-killer doesn't reduce pain or shorten recovery
Forty-five years ago: FOOTPRINTS FOUND ON MOON
NASA won't be back any time soon, sadly
prev story

Whitepapers

Designing a Defense for Mobile Applications
Learn about the various considerations for defending mobile applications - from the application architecture itself to the myriad testing technologies.
Implementing global e-invoicing with guaranteed legal certainty
Explaining the role local tax compliance plays in successful supply chain management and e-business and how leading global brands are addressing this.
Top 8 considerations to enable and simplify mobility
In this whitepaper learn how to successfully add mobile capabilities simply and cost effectively.
Seven Steps to Software Security
Seven practical steps you can begin to take today to secure your applications and prevent the damages a successful cyber-attack can cause.
Boost IT visibility and business value
How building a great service catalog relieves pressure points and demonstrates the value of IT service management.