Killer Whales Have Begun Preying On Sea Otters, Causing Disruption Of Coastal Ecosystems In Western Alaska

ported by several lines of evidence, Estes said. First is the sudden increase in observed attacks. A careful statistical analysis found it extremely unlikely that the cluster of recent observations was due to chance alone.

The researchers also compared sea otter populations at two sites on Adak Island, one an open bay and the other an area inaccessible to killer whales. From 1993 through 1997, sea otter numbers were stable in the protected Clam Lagoon, while in the adjacent Kuluk Bay they declined by 76 percent.

According to calculations based on the team's observations in one section of the Aleutian Islands, killer whales must have killed 6,788 sea otters per year between 1991 and 1997 to account for the observed decline in the population. Taking into account the number of hours of field observations by the research team during this period, the number of those attacks they could expect to have observed is 5.05, which is very close to the actual number of six observed attacks.

The researchers ruled out other possible causes of the sea otter decline, such as disease, toxins, and starvation, Estes said.

"It took about two years for me to become convinced that killer whales were responsible, as we dismissed one possibility after another and gradually gathered direct evidence pointing to killer whales," Estes said.

Terrie Williams, an associate professor of biology at UCSC and coauthor of the paper, analyzed the caloric value of sea otters, which are a less nutritious food source than killer whales' usual prey because they have very little blubber. Williams estimated that a single killer whale would need to eat 1,825 otters per year to meet its energy requirements. These figures suggest that as few as four killer whales feeding exclusively on sea otters could have driven the population decline observed over a large area of the Aleutian archipelago.

Sea otters were nearly extinct by the early 20th century due to overhunting for the fur trade. Pr

Contact: Tim Stephens
University of California - Santa Cruz

Page: 1 2 3 4

Related biology news :

1. Killer virus
2. Tracking A Killers Progression
3. USGS Finds Sea Otters At Risk From Killer Whales In A Changing Ocean
4. French Researchers Breed Flightless Ladybirds As Pest-Killers
5. University Of Kentucky Researcher Awarded MERIT Extension For Study Of Third World Killer
6. How A Common Protein Becomes A Cancer Killer
7. Weevils Wipe Out Killer Weeds In Papua New Guinea
8. Virginia Tech Scientists Study Killer Molecules
9. Whales, seals or men? Who stole all the fish?
10. Whales get the bends
11. Whales drawn to waters off Mississippi River Delta

Post Your Comments:

(Date:11/12/2015)... golden retriever that stayed healthy despite having the gene ... new lead for treating this muscle-wasting disorder, report scientists ... and Harvard and the University of São Paolo in ... pinpoints a protective gene that boosts muscle regeneration, ... Children,s lab of Lou Kunkel , PhD, is ...
(Date:11/10/2015)... Nov. 10, 2015 About ... that helps to identify and verify the identity ... considered as the secure and accurate method of ... a particular individual because each individual,s signature is ... especially when dynamic signature of an individual is ...
(Date:10/29/2015)... Oct. 29, 2015   MedNet Solutions , an ... spectrum of clinical research, is pleased to announce that ... Association (MHTA) as one of only three finalists for ... – Small and Growing" category. The Tekne Awards honor ... shown superior technology innovation and leadership. ...
Breaking Biology News(10 mins):
(Date:11/24/2015)... LUMPUR, Malaysia , Nov. 24, 2015 /PRNewswire/ ... global contract research organisation (CRO) market. The trend ... result in lower margins but higher volume share ... increased capacity and scale, however, margins in the ... Research Organisation (CRO) Market ( http://www.frost.com/sublib/display-report.do?id=P86A-01-00-00-00&src=PR ), ...
(Date:11/24/2015)... 2015 Halozyme Therapeutics, Inc. (NASDAQ: HALO ) will ... New York on Wednesday, December 2 at 9:30 a.m. ... and CEO, will provide a corporate overview. th ... at 1:00 p.m. ET/10:00 a.m. PT . Jim Mazzola ... a corporate overview. --> th Annual Oppenheimer Healthcare ...
(Date:11/24/2015)... ... November 24, 2015 , ... ... the year and one of the premier annual events for pharmaceutical manufacturing: 2015 ... 8–11 November 2015, where ISPE hosted the largest number of attendees in more ...
(Date:11/24/2015)... 2015 --> ... "Oligonucleotide Synthesis Market by Product & Services (Primer, Probe, ... DNA, RNAi), End-User (Research, Pharmaceutical & Biotech, Diagnostic Labs) ... market is expected to reach USD 1,918.6 Million by ... CAGR of 10.1% during the forecast period. ...
Breaking Biology Technology:
Cached News: