[OANNES Foro] Whales and dolphins change the way they communicate in a noisy ocean

Mario Cabrejos casal en infotex.com.pe
Lun Oct 29 08:23:41 PDT 2018


Whales and dolphins change the way they communicate in a noisy ocean

by  <https://news.mongabay.com/by/ongabay-com/> Mongabay.com 

26 October 2018

https://news.mongabay.com/2018/10/whales-and-dolphins-change-the-way-they-co
mmunicate-in-a-noisy-ocean/

Noise from ships changes the way that whales and dolphins communicate with
each other, according to two studies published this week.

Marine biologists know that an increasingly cacophonous ocean, filled with
the din from shipping, seismic surveys and sonar, is undoubtedly impacting
the animals that live there. Loud noises could be damaging the hearing of
marine mammals that are dependent on sound as a way of making sense of their
three-dimensional world, and sonar blasts have been
<https://news.mongabay.com/2013/09/sonar-used-by-oil-company-caused-mass-wha
le-stranding-in-madagascar/> linked to the mass stranding of whales around
the world.

Now, two independent teams of scientists have shown that whales and dolphins
alter the sounds that they make in response to the whirr of ships.

University of Maryland marine biologist Helen Bailey and her team recorded
the whistles of bottlenose dolphins (Tursiops truncatus) off the coast of
the U.S. state of Maryland and
<http://rsbl.royalsocietypublishing.org/content/14/10/20180484> published
their work Oct. 24 in the journal Biology Letters. The researchers analyzed
the characteristics of those calls and took note when they changed. They
found that when there was more ambient sound, mostly from passing boats and
ships, the dolphins switched to higher frequencies and streamlined their
whistles.

"It's kind of like trying to answer a question in a noisy bar and after
repeated attempts to be heard, you just give the shortest answer possible,"
Bailey said
<https://eurekalert.org/pub_releases/2018-10/uomc-gni102418.php> in a
statement. "Dolphins simplified their calls to counter the masking effects
of vessel noise."

A second team of scientists, led by biologist Koki Tsujii of the Ogasawara
Whale Watching Association and Hokkaido University in Japan, looked at the
changes in the songs of whales - humpbacks (Megaptera novaeangliae), in this
case. Publishing their results in the journal PLOS ONE, also on Oct. 24,
they recorded the changes in the songs sung by male humpbacks as a ship
carrying passengers and cargo motored by.

The team's recordings of 26 singing whales revealed that when the ship
passed and the singing whales were less than about 1,200 meters (3,940 feet)
from the ship, they tended to cut their songs short. What's more, they often
wouldn't start up again for half an hour. They also weren't as likely to
hang around and sing at distances of less than 500 meters (1,640 feet) from
the ship's path.

The researchers note that, because only the males sing in an effort to
attract females, they can't be certain of how the noise impacts young and
female humpbacks. But it's clear that the sounds are changing behaviors, the
authors said.

"Humpback whales seemed to stop singing temporarily rather than modifying
sound characteristics of their song under the noise, generated by a
passenger-cargo liner," the authors of the PLOS ONE paper said
<https://www.eurekalert.org/emb_releases/2018-10/p-mhw101718.php> in a
statement. "Ceasing vocalization and moving away could be cost-effective
adaptations to the fast-moving noise source."

The team suggests that more research would help determine if these sounds
increased the stress levels of the affected humpbacks.

The authors of the dolphin study raised similar concerns.

"These whistles are really important," Bailey said in the statement. "Nobody
wants to live in a noisy neighborhood. If you have these chronic noise
levels, what does this mean to the population?"

She and her colleagues suggest that, in the presence of these levels of
ambient sound, dolphins might have trouble getting their full message across
to other members of their species.

"[The] noise-induced simplification of dolphin whistles may reduce the
information content in these acoustic signals and decrease effective
communication, parent-offspring proximity or group cohesion," the authors
write.

Citations 

Fouda, L., Wingfield, J. E., Fandel, A. D., Garrod, A., Hodge, K. B., Rice,
A. N., & Bailey, H. (2018). Dolphins simplify their vocal calls in response
to increased ambient noise. Biology Letters, 14(10).

Tsujii, K., Akamatsu, T., Okamoto, R., Mori, K., Mitani, Y., & Umeda, N.
(2018). Change in singing behavior of humpback whales caused by shipping
noise. PLOS ONE, 13(10), e0204112.

 



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