Subscription Services: Subscribe | Change | Unsubscribe | RSS
Advertising Media Kit: Introduction | Stats/Demographics | Rates | Testimonial | Contact
Miscellaneous: Reference Desk | Sitemap
Related Reading
Researchers: Whales May Turn Down Their Hearing Sensitivity When Warned Of An Impending Loud Noise
email to a friend email print this print      Bookmark and Share   RSS 2.0 feed

TOKYO,Japan -- Toothed whales navigate through sometimes dark and murky waters by emitting clicks and then interpreting the pattern of sound that bounces back. The animals' hearing can pick up faint echoes, but that sensitivity can be a liability around loud noises. Now researchers have discovered that whales may protect their ears by lowering their hearing sensitivity when warned of an imminent loud sound. The scientists will present the finding at the Acoustics 2012 meeting in Hong Kong, May 13-18, a joint meeting of the Acoustical Society of America (ASA), Acoustical Society of China, Western Pacific Acoustics Conference, and the Hong Kong Institute of Acoustics.

"Whale hearing may be the most fascinating marine mammal sense," says Paul Nachtigall, a biologist at the University of Hawaii who started his career studying otter vision, but soon switched to whale and dolphin echolocation. Earlier experiments by Nachtigall and his colleagues suggested that whales can actively shield their hearing from loud outgoing echolocation clicks, which can reach sound levels equivalent to a rifle fired right next to the ear. The scientists wondered if the animals could similarly protect their ears from incoming loud noises.

The team repeatedly played a short warning sound followed by a loud sound to a false killer whale working in the laboratory in a floating facility off Coconut Island at the Hawaii Institute of Marine Biology. They measured the animal's hearing sensitivity by placing suction-cup sensors on the skin of the whale's head and recording the frequency of its brainwaves. Initial results indicate that the whale significantly reduces its hearing sensitivity when warned that a very loud noise is about to arrive.

"It appears as though the whales learn this pairing of warning signal and loud sound rapidly through classical conditioning," says Nachtigall. Many human activities such as oil exploration and the use of ships' sonar create loud noises in the ocean. If wild whales could quickly learn the meaning of a short warning sound, the technique might help lessen the impact of anthropogenic noise on marine mammals, Nachtigall notes.

Whales' auditory systems are similar to other mammals' in structure, but larger in size, most likely because they have evolved for the special task of echolocation. Right now scientists aren't certain how the whales are able to adjust their hearing sensitivity. Bats, which also use sound to navigate, automatically contract muscles in their ears to reduce hearing sensitivity while they produce loud outgoing echolocation calls. Nachtigall says that whales may do something similar, but that understanding the mechanism will take considerably more work. "We think based on much of our echolocation work that it is much more than a simple reflex," he says.

So far, the team has only tested the warning signals with one false killer whale. In the future they would like to test additional species of marine mammals. "We are also very interested in how long it takes a nave animal to learn to lower its sensitivity when warned," Nachtigall says.

Views expressed in this article do not necessarily reflect those of UnderwaterTimes.com, its staff or its advertisers.

Reader Comments

2 people have commented so far. cloud add your comment

This is very interesting information, but at what cost to the animal living in a laboratory? They gained knowledge from a CAPTIVE false killer whale kept captive for research? I dearly hope to live long enough to see laws enacted that prohibit researchers from taking marine mammals from their natural homes so they can be studied. We should not do to any animal what we would not want done to our own children. Free the poor whale and study them in the wild.
   comment# 1   - Teresa Wagner · Carmel, CA · May 9, 2012 @ 9:26am

Unfortunately, its still better than taking animals away from their homes for entertainment, i.e. some aquariums. Though I do know often times these are rescued animals that cannot survive in the wild. It is still a case of the lesser of two evils, study one animal to save one thousand.
   comment# 2   - Sebastian Skerhut · San Antonio, Tx, USA · Mar 12, 2013 @ 11:27am
Add your comment


characters left

*required field.
Note: Comments are posted if they are not abusive and are compliant with our Terms and Conditions. Comments with foul language will be deleted without exception.

   


bottom_left
bottom_right
Privacy Policy     © Copyright 2014 UnderwaterTimes.com. All rights reserved