Natural Environment Blog

Dolphins can be deafened by loud noises, which can lead to death.

A new study has found that loud sonar can cause deafness in dolphins.

The study found that loud, repeated blasts of sonar caused dolphins to temporarily lose their hearing for 20 to 40 minutes.

Published in the British journal Biology Letters on Wednesday, the findings could provide further evidence that human made noises can be attributed to dolphin and whale deaths. 

The study, led by Aran Mooney Marine Biologist at the University of Hawaii, exposed an Atlantic bottlenose dolphin to progressively louder pings of mid-frequency sonar. The dolphin was born in captivity and was trained. 

A suction cup was fitted to the dolphin’s head, with a sensor attached that monitored the animal’s brainwaves.

“What we found was if you play sound you can cause temporary hearing loss. The sounds have to be surprisingly loud and they have to be repeated over an extended period of time – two to three minutes.” Mooney said. “In that time you would expect them to swim away as fast as possible. They have to be within 40 metres of a ship, but when you have certain oceanographic conditions it’s hard for the animals to get out of the way.” 

Many people believe that human made noises, also referred to as acoustic smog, has been the cause of whale and dolphin beachings around the world.

Mooney acknowledges that, given the study was undertaken in a lab with a captive-born dolphin, it does not provide proof that military sonar is to blame for mass strandings. 

“We definitely showed that there are physiological and some behavioural effects [from repeated, loud sonar], but to extrapolate that into the wild, we don’t really know,” Mooney told AFP.

Rescuers help a beached pilot whale in Tasmania, Australia. Photo: Tasmanian Department of Primary Industry and Water.

Australian volunteers have helped save 11 pilot whales from death in a mass stranding on a beach in Tasmania, Australia.

Around 60 volunteers joined 15 government officers to keep the beached whales alive while transporting them to a nearby beach with deeper water. 

The whales were found stranded on Saturday at Anthony’s Beach, near Stanley on the north-west coast of Tasmania, Australia.

53 Whales Died

In total, 64 mothers and calves were stranded, but only 12 were alive when they were found.

The rescuers spent the night keeping the remaining whales from overheating by splashing water over them. Out of the 12 remaining whales, one died while being returned to the water at Godfreys Beach, around 17 kilometers away. 

An Outstanding Effort

While 11 surviving whales vs 53 dead whales might not sound like an outstanding success, whale rescue efforts are known for their low success rates. Many efforts fail to save even one beached whale.   

“The efforts of the volunteers and the Circular Head community has been outstanding.” said Parks and Wildlife Services manager Chris Arthur, who co-ordinated the rescue effort.

“They gave up a weekend. People got sunburnt. People got engaged with these animals,” he said.

“We used specially built car trailers, which we were able to put up to two whales in each. And we transported those animals 17 kilometres (11 miles) to Godfrey’s Beach,” Arthur said.

Satellite Tracking

Before the whales were released back into the sea, the team attached satellite trackers to their dorsel fins. This will help the team keep track of the whales’ progress.

The satellite trackers can transmit the whales’ location to a datacenter in France. The team is then able to access that information from Australia.  

Great Progress So Far

According to data received from the satellite this morning, the whales’ progress looks good so far. Information from the satellite showed that the whales were swimming east across Bass Strait.

“Even though we released the whales because of the weather conditions over about a three-hour period, it [the satellite data] told us that those whales did regroup at sea.” said Rosemary Gales, a scientist involved in the rescue effort.

“We can’t keep track of the whales in the boats when they power off and they disappear into the distance but we now know from the satellite information that they did regroup and they have been travelling together as a pod - which is absolutely fantastic news because it does make us think that the rescue was a success.” she continued.

Mystery

Whale beachings occur periodically across Australia and New Zealand. The reason why whales beach themselves remains a mystery. Some scientists believe that it’s due to acoustic smog - human made noise that can disorientate whales and other marine life.

I’ve been reading a little about ‘acoustic smog’ and its affect on marine life within our oceans.

Acoustic smog is basically another way of saying ‘noise pollution’. In particular, it is a term often used to describe the noise in our oceans that come from man-made sources. This typically includes sources such as:

The Impact of Acoustic Smog on Nature

It seems that acoustic smog could be having a devastating affect on the whales, dolpins, and other mammals in our oceans. Sound plays an important part in the survival of the 80 or so cetacean species, which includes whales, dolpins and porpoises.

Because these animals use acoustic signals for orientation, reproduction, and even feeding, the introduction of man-made noises over the last hundred years or so appears to be impacting on the cetaceans’ ability to do these things. There’s also widespread concern that acoustic smog is directly contributing to the death of many cetaceans. 

It is thought that the affects of acoustic smog on cestaceans include:

• displacement
• avoidance reactions
• collisions with ships
• mass stranding
• hearing damage
• death

Furthermore, evidence strongly suggests that man-made noise often causes lesions in acoustic organs of cestaceans, which are severe enough to cause death. 

Further Research

Unfortunately, there isn’t enough scientific knowledge to be able to come to strong conclusions on understanding the relationships of frequencies, intensities, and duration of exposures in producing damage. More research needs to be done in this area, and many research bodies are appealing for assistance in this area.

Sons de Mar, for example, say this about their continued efforts in this area:

Academic research generally depends on external funding through public channels and commercial companies. Since the effects of noise pollution on the marine environment have not yet been completely implemented in national programs, funding through these sources is limited.

And:

Therefore, we appeal to private sources to guarantee the continuity of this research. ‘Sons de Mar’ (Sounds of the Sea) was created as a public interface aimed at involving society through donations that will allow to collaborate with all the aspects of the scientific work.

The impact of dangerous sonor on marine life is not a new concern. The Cetacean Society International (CSI) website provides articles on this subject dating as far back as 1995. 

Also, the Natural Resources Defense Council (NRDC) first wrote a report on this subject in 1999. The report has since been updated and is called Sounding the Depths II: The Rising Toll of Sonar, Shipping and Industrial Ocean Noise on Marine Life. The online report includes an acompanying movie, narrated by Pierce Brosnan.