Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Manatee hearing good enough to sense approaching motorboats

12.04.2012
Grazing sea grass along the subtropical Florida coast, manatees would seem to have a peaceful life. But motorboats and other watercraft can injure the mammals, sometimes shattering their ribcages or leaving scars from collisions.

Joe Gaspard from the Mote Marine Laboratory and Aquarium, USA, explains that many factors put manatees at risk and it isn't clear why the animals are so vulnerable to human activity. For more than 14 years, Mote research has focused on how manatees use their senses to perceive their environment in an effort to understand the factors that put manatees at risk.

Their studies have already shown that manatees' vision is poor, compounded by the turbid and tannic waters where they spend much of their lives. But can manatees hear boats? And can they hear them above the cacophony of sounds in their natural environment? Sound is absorbed less in water than in air, potentially allowing it to travel farther. It also travels five times faster in water than in air, theoretically warning the animals earlier of an approaching threat, Gaspard said. Teaming up with Gordon Bauer, Roger Reep and David Mann, and a group of trainers from the aquarium, Gaspard tested the hearing of two resident manatees, Buffett and Hugh – the world's only manatees trained to participate in behavioural research and husbandry procedures – to find out what they are capable of hearing. The discovery, published in The Journal of Experimental Biology at http://jeb.biologists.org, indicates that manatees can hear within the frequency range where boats operate but lead to new questions about why manatees remain at risk.

'Buffett and Hugh are very cooperative and picked up on the elements of the study quickly', remembers Gaspard, who worked with Kim Dziuk, Adrienne Cardwell and LaToshia Read to train the animals to swim down to a listening station 1 m beneath the surface. Switching on a light to indicate to the animals that a test was about to start, the team then trained the manatees to touch a yellow response paddle in return for a tasty fruit or vegetable snack when they heard a sound. They also trained the manatees to stay in place (in return for another snack) when they heard nothing. Once Hugh and Buffett had got the task in hand, the team tested their hearing by selecting a particular sound frequency (pitch) and gradually lowering the volume of the sound until the manatee could no longer hear it. Plotting these 'hearing thresholds' on a graph, the team could see that the manatees had good hearing between 8 and 32kHz and could even hear sounds as low as 0.25kHz – so long as they were quite loud. However, they were even more amazed when Buffett appeared to be able to hear ultrasonic frequencies as high as 90.5kHz. 'Buffett did the task but refused to continue after the first round at that frequency, so we think it was aversive or annoying', Gaspard recalls.

Intrigued by the manatees' apparently sensitive hearing, the team then tested how well the mammals performed when the sounds were accompanied by background noise. Playing test tones – ranging from 4 to 32kHz – against background noise centered on the same pitch, the team recorded the difference between the volume of the tone and background noise when the manatee could no longer distinguish the tone. Plotting the critical ratio – the level at which the background noise swamped the manatee's hearing – against pitch for each animal, the team saw that the manatees struggled to hear lower and higher pitched sounds above background noise. However, their hearing was much sharper at 8kHz – the frequency at which manatees communicate – where they could still distinguish tones that were only 18.3dB louder than the background.

So, it appears that manatees should be able to hear approaching motorboats above background noise — but it's much more difficult to know whether manatees can always focus on these sounds in nature, Gaspard says. 'Manatees might be less aware of these sounds when they are sleeping, eating or performing other activities related to their daily lives that require their full attention,' says Gaspard. "There are also a multitude of environmental factors that come into play. Understanding how animals use their various senses is a complex process. Could their sense of touch also be playing a role here? We are working on that question now."

IF REPORTING ON THIS STORY, PLEASE MENTION THE JOURNAL OF EXPERIMENTAL BIOLOGY AS THE SOURCE AND, IF REPORTING ONLINE, PLEASE CARRY A LINK TO: http://jeb.biologists.org/content/215/9/1442.abstract

REFERENCE: Gaspard, J. C. III, Bauer, G. B., Reep, R. L., Dziuk, K., Cardwell, A., Read, L. and Mann, D. A. (2012). Audiogram and auditory critical ratios of two Florida manatees (Trichechus manatus latirostris). J. Exp. Biol. 215, 1442-1447.

This article is posted on this site to give advance access to other authorised media who may wish to report on this story. Full attribution is required, and if reporting online a link to jeb.biologists.com is also required. The story posted here is COPYRIGHTED. Therefore advance permission is required before any and every reproduction of each article in full. PLEASE CONTACT permissions@biologists.com

Kathryn Knight | EurekAlert!
Further information:
http://www.biologists.com
http://jeb.biologists.org/content/215/9/1442.abstract

More articles from Life Sciences:

nachricht Transport of molecular motors into cilia
28.03.2017 | Aarhus University

nachricht Asian dust providing key nutrients for California's giant sequoias
28.03.2017 | University of California - Riverside

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A Challenging European Research Project to Develop New Tiny Microscopes

The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.

To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Transport of molecular motors into cilia

28.03.2017 | Life Sciences

A novel hybrid UAV that may change the way people operate drones

28.03.2017 | Information Technology

NASA spacecraft investigate clues in radiation belts

28.03.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>