Featured Research

from universities, journals, and other organizations

Silent stalkers of dark ocean waters: Killer whales hunt marine mammals at night in near total darkness

Date:
December 3, 2013
Source:
Acoustical Society of America (ASA)
Summary:
The mating roar of a male harbor seal is supposed to attract a partner, not a predator. Unfortunately for the seals, scientists have found evidence that marine-mammal-eating killer whales eavesdrop on their prey. Previous research had shown mammal-eating killer whales are nearly silent before making a kill, neither vocalizing nor using their echolocation. The likely reason, researchers say, is the excellent hearing of the seals, porpoises, and other animals the whales stalk.

Harbor seal laying on rocks.
Credit: hotshotsworldwide / Fotolia

The mating roar of a male harbor seal is supposed to attract a partner, not a predator. Unfortunately for the seals, scientists have found evidence that marine-mammal-eating killer whales eavesdrop on their prey. The researchers will present their work at the 166th Meeting of the Acoustical Society of America (ASA), held Dec. 2 -- 6 in San Francisco, Calif.

Related Articles


Previous research had shown mammal-eating killer whales are nearly silent before making a kill, neither vocalizing nor using their echolocation. The likely reason, says Volker Deecke, a researcher at the Centre for Wildlife Conservation at the University of Cumbria in the U.K., is the excellent hearing of the seals, porpoises, and other animals the whales stalk.

"If the mammal hunters just swam around clicking all the time, then all the prey would be warned," he said. "It looks like the whales are using a stealth approach instead."

While biologists had evidence that the whales do not echolocate while hunting, they were still unsure exactly how the animals do find their prey in the murky northern waters off the west coast of North America. To help answer that question Deecke and his colleagues traveled to Alaska and placed acoustic recording tags on 13 killer whales over the course of a two-year study.

The tags, which are about the size of a cell phone, were attached to the whales with four suction cups and could stay on for up to 16 hours. The tags' accelerometers, compass, depth sensor, and hydrophone recorded data on the animals' movements and any sounds it heard or made. Deecke and his colleagues were able to identify predation events by the characteristic sound of a whale dispatching its prey with a hit from its tail fluke.

After analyzing many hours of data, Deecke and his team found that killer whales were successfully locating prey even in near-complete darkness. Deecke notes that this new evidence of nighttime hunting rules out visual cues as the only means of prey detection.

"We now suspect that mammal-eating killer whales are primarily eavesdropping on sounds generated by their prey to find food," he said. Deecke recounted one unfortunate seal whose demise was captured by the sensors in an acoustic story of life and death.

"As soon as we put one of the tags on, it started to record seal roars, which are part of the display that male harbor seals use to attract females. Over the next half-hour the roars got louder and louder, then there are a sequence of three quite loud roars that suggest the seal is within a few hundred meters of the killer whale. Twenty-seven seconds later there are the sounds of a predation event, and then no more roars."

Deecke notes that such a story is compelling but does not provide direct evidence that killer whales are tuning in to the sounds of their prey. Going forward, he hopes to use playback experiments to test killer whales' responses to recorded seal roars and porpoise echolocation clicks.

Finding out how much killer whales rely on acoustic cues to hunt could help scientists better understand the potential ecological impact of shipping noise and other activities that generate underwater sound. "We need to understand how the foraging process works so that we, as humans, can know how our behavior might impact the animals negatively and what we can do to minimize our impact," Deecke said.


Story Source:

The above story is based on materials provided by Acoustical Society of America (ASA). Note: Materials may be edited for content and length.


Cite This Page:

Acoustical Society of America (ASA). "Silent stalkers of dark ocean waters: Killer whales hunt marine mammals at night in near total darkness." ScienceDaily. ScienceDaily, 3 December 2013. <www.sciencedaily.com/releases/2013/12/131203141753.htm>.
Acoustical Society of America (ASA). (2013, December 3). Silent stalkers of dark ocean waters: Killer whales hunt marine mammals at night in near total darkness. ScienceDaily. Retrieved October 24, 2014 from www.sciencedaily.com/releases/2013/12/131203141753.htm
Acoustical Society of America (ASA). "Silent stalkers of dark ocean waters: Killer whales hunt marine mammals at night in near total darkness." ScienceDaily. www.sciencedaily.com/releases/2013/12/131203141753.htm (accessed October 24, 2014).

Share This



More Plants & Animals News

Friday, October 24, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Black Bear Cub Goes Sunday Shopping

Black Bear Cub Goes Sunday Shopping

Reuters - Light News Video Online (Oct. 23, 2014) Price check on honey? Bear cub startles Oregon drugstore shoppers. Rough Cut (no reporter narration). Video provided by Reuters
Powered by NewsLook.com
Dances With Wolves in China's Wild West

Dances With Wolves in China's Wild West

AFP (Oct. 23, 2014) One man is on a mission to boost the population of wolves in China's violence-wracked far west. The animal - symbol of the Uighur minority there - is under threat with a massive human resettlement program in the region. Duration: 00:41 Video provided by AFP
Powered by NewsLook.com
Breakfast Debate: To Eat Or Not To Eat?

Breakfast Debate: To Eat Or Not To Eat?

Newsy (Oct. 23, 2014) Conflicting studies published in the same week re-ignited the debate over whether we should be eating breakfast. Video provided by Newsy
Powered by NewsLook.com
Weird-Looking Dinosaur Solves 50-Year-Old Mystery

Weird-Looking Dinosaur Solves 50-Year-Old Mystery

Newsy (Oct. 23, 2014) You've probably seen some weird-looking dinosaurs, but have you ever seen one this weird? It's worth a look. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins