Free Newsletters - Space News - Defense Alert - Environment Report - Energy Monitor
. Earth Science News .




WHALES AHOY
Harbor porpoises can thank their worst enemy for their success
by Staff Writers
Odense M, Denmark (SPX) Jun 14, 2013


Harbor porpoises manage very well in coastal and busy -- and potential dangerous -- waters. This photograph is from Denmark. Credit: Rune Dietz.

The harbor porpoise (Phocoena phocoena) is a whale species that is doing quite well in coastal and busy waters. They are found in large numbers throughout the Northern Hemisphere from Mauritania to Alaska, and now researchers from the University of Southern Denmark explain why these small toothed whales are doing so well: The harbor porpoise can thank their worst enemy, the killer whale, for their success.

Coastal areas are more challenging and potentially dangerous for a small whale. There is a risk of beaching and being caught in a fisherman's net, but there are also benefits. Fish are plentiful and easier to find in coastal waters than in the open sea.

Therefore, coastal waters are attractive for porpoises, and they are extremely skilled at navigating, locating prey and avoiding hazards near the coast. Like other toothed whales porpoises use echolocation for orientation and to detect prey. They emit a constant stream of sonar clicks, which, when these hit a rock, a fish or a ship nearby an echo is sent back to the porpoise. From the echo, the porpoise can distinguish the location of the object and often also can identify the object.

Porpoises can locate even small fish and small objects such as net floats and fine fishing nets. This ability sets them apart from many other toothed whales, which do not have such sophisticated echolocation abilities. The secret of this ability is that the porpoise uses very short clicks and these are higher in frequency than those of many other toothed whales, explains Lee Miller from the Institute of Biology, University of Southern Denmark (SDU).

Porpoise clicks last just a hundred-millionth of a second, and are about 130 kHz. For comparison, a human can hear up to 20 kHz and a dog up to about 60 kHz.

Lee Miller and his colleague Magnus Wahlberg, also from the Institute of Biology, SDU, now believe that they have found an explanation why porpoise clicks are so high in frequency. They point at the porpoise's greatest enemy: the killer whale. This is one of their conclusions in a research article in the journal Frontiers in Physiology.

"Over millions of years the porpoise has evolved its ability to emit very high frequency click sounds that killer whales have difficulty hearing since they cannot hear sounds that are much higher than about 100 kHz. Killer whale hearing is best at around 20 kHz, so it is hard for them to detect a porpoise", explains Lee Miller.

The ancestor of whales emerged about 50 million years ago, and the first toothed whales began to use echolocation about 30 million years ago.

"5-10 million years ago the killer whale emerged and then evolution began to favor the toothed whales that could avoid being captured by killer whales. One way to avoid being eaten was to emit echolocation sounds that were difficult for killer whales to detect - thus an ability favored by evolution, "concludes Lee Miller and Magnus Wahlberg in their research article.

Strange as it may sound, porpoises can thank their worst enemy, the killer whale, that they are doing so well in coastal and busy waters.

But why do many species of porpoises and other small toothed whales emit echolocation sounds at about 130 kHz? Why not click at even higher frequencies?

"These frequencies are the most effective for porpoises. Besides avoiding killer whales, there is another advantage: It is also at these frequencies that natural noise in the ocean is the lowest. Thus porpoises can better hear the echoes from objects and prey when using these clicking sounds, "explains Lee Miller.

Ref: Miller, L. A. and Wahlberg, M. (2013). Echolocation by the harbor porpoise: Life in coastal waters. In Frontiers in Integrative Physiology, vol 4 (ML Melcon ed.), pp. 1-6: Frontiers.

.


Related Links
University of Southern Denmark
Follow the Whaling Debate






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News





WHALES AHOY
Stranded orcas hold critical clues for scientists
Davis CA (SPX) Jun 12, 2013
The development of a standardized killer-whale necropsy system has boosted the complete data from killer-whale strandings from 2 percent to about 33 percent, according to a recent study from a team of scientists, including a University of California, Davis wildlife veterinarian. The study, published recently in the journal Marine Mammal Science, suggests that the data can help scientists b ... read more


WHALES AHOY
Sandbags and raw nerves as flood peak hits Germany

More radioactive leaks reported at Fukushima plant

Japan disaster cash spent on counting turtles: report

Agreement over Statue of Liberty security screening

WHALES AHOY
Chilean, U.S. firms join effort to expand e-waste recycling

Space Debris - One Solution

Moon Radiation Findings May Reduce Health Risks to Astronauts

Sony eyes long game despite console launch triumph

WHALES AHOY
Ethiopia endorses Nile share deal, amid row with Egypt

Drought, river fragmentation forcing endangered fish out of water

AU urges Egypt and Ethiopia to hold talks on Nile row

Unfrozen mystery: H2O reveals a new secret

WHALES AHOY
Ancient trapped water explains Earth's first ice age

US senators urge Obama to block Alaska mine

Is a Sleeping Climate Giant Stirring in the Arctic

NASA's IceBridge Mission Contributes to New Map of Antarctica

WHALES AHOY
URI, firm developing techniques for tuna aquaculture

How does inbreeding avoidance evolve in plants

How do you feed nine billion people

China approves imports of GM soybean from Brazil

WHALES AHOY
Hungary president slams lagging EU flood aid

Seismic safety of light-frame steel construction being tested

Germany eyes 8bn-euro fund for flood victims: reports

Merkel urges greater flood protection as tours region

WHALES AHOY
First pictures of Algeria's Bouteflika since mini-stroke

Gunfire at paramilitary barracks in Niger capital: residents

'Scorched earth' tactics in Sudan's Blue Nile: Amnesty

Rwandan general to command Mali UN force

WHALES AHOY
Penn Research Indentifies Bone Tumor in 120,000-Year-Old Neandertal Rib

Weapons testing data determines brain makes new neurons into adulthood

World's 'oldest woman' dies in China: family

Geneticist speculates humans could have big eyes, foreheads in future




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement