Featured Research

from universities, journals, and other organizations

Troubling News About Sea Otter Deaths

Date:
May 8, 2003
Source:
University Of California - Davis
Summary:
A new UC Davis analysis finds that adult sea otters in California in 1998-2001 died in unusually high numbers from newly recognized diseases and in geographic clusters -- all of which suggest that their coastal environment may be so substantially altered that the species could be in jeopardy.

A new UC Davis analysis finds that adult sea otters in California in 1998-2001 died in unusually high numbers from newly recognized diseases and in geographic clusters -- all of which suggest that their coastal environment may be so substantially altered that the species could be in jeopardy.

Related Articles


The findings are particularly worrisome in the wake of last week's report that a startling 100 southern sea otters have washed up dead on California beaches since January -- 100 deaths in a population that has been falling overall since 1995 and now stands at about 2,000.

The new analysis, done in collaboration with the California Department of Fish and Game, does not include those 100 otters, but its findings may help researchers understand their deaths.

"We are very concerned that the otters are dying so frequently of diseases. This indicates that the ecosystem is very unhealthy," said wildlife epidemiologist Jonna Mazet, director of the UC Davis Wildlife Health Center and leader of the campus' longstanding otter-research programs.

The new study identifies the most important causes of otter deaths in California and determines where otters are most at risk. It reviews 105 deaths of southern sea otters (Enhydra lutris nereis) -- all the beached carcasses found in California from February 1998 through June 2001, the most recent period for which complete data are available.

The lead analyst was Christine Kreuder, a veterinarian at the UC Davis Wildlife Health Center and a doctoral student in epidemiology. Her chief collaborator was Melissa Miller, a UC Davis wildlife veterinarian who has been performing otter necropsies for Fish and Game since 1998.

The researchers' key findings:

In a healthy population, juvenile and aged otters should account for most deaths. But the UC Davis/Fish and Game analysis found that the largest proportion of dead otters -- 47 percent -- were 4 to 9 years old. That is the age when the animals should have been most healthy. These prime-breeding-age otters are necessary for population growth. Many deaths in this age group would make it difficult for otter populations to recover.

Nearly two-thirds of the otters -- 64 percent -- died of some form of disease. A surprising 38 percent of the disease group died from parasitic infections, including thorny-headed worms (acanthocephalans) and protozoa (Toxoplasma gondii and Sarcocystis neurona).

The study even identified a new cause of death -- heart disease -- and researchers are pursuing the underlying cause.

The study was also the first to show that otters with Toxoplasma infections were four times more likely to be killed by sharks than those without.

"This parasite invades the otter's brain and can cause neurological problems such as seizures," Kreuder said. "That could make the otters confused and disabled. They would be less able to evade sharks, more likely to swim to unprotected offshore waters, and more likely to shake and twitch, which attracts sharks." Shark attacks were clustered between Point Ano Nuevo and Santa Cruz.

Two geographic clusters of disease were identified. First, half of the otters found near the town of Morro Bay had died of Toxoplasma brain infections.

Protozoal parasites kill otters by causing encephalitis (fatal brain infections). The only known source of these parasites is the feces of two land mammals not native to California -- domestic cats for Toxoplasma and opossums for Sarcocystis. UC Davis has another study under way to find out how those parasites are getting from the land into the ocean; storm-drain water runoff is one suspect.

The second cluster was due to acanthocephalan worm infections, which killed five of the six otters found in a 1.25-mile stretch of southern Monterey Bay.

Sea otters become infected with acanthocephalans when their diet is unusually high in sand crabs, which carry the worms. In the otters, the worms migrate from the intestine to the abdominal cavity, causing fatal infections.

"Because we did not see these two causes of death distributed evenly along the coast, we know that otters are at high risk in these areas," Kreuder said.

In addition to Kreuder and Miller, the analysis was conducted by Jonna Mazet, who is Kreuder's doctoral adviser; David Jessup, a senior veterinarian at Fish and Game's marine wildlife center in Santa Cruz and Miller's supervisor; UC Davis veterinary pathologist Linda Lowenstine, parasitologist Patricia Conrad and epidemiologist Tim Carpenter; and Fish and Game biologists Mike Harris and Jack Ames.

The study was funded by the University of California Marine Council Coastal Environmental Quality Initiative, the Morris Animal Foundation and the PKD Trust.

Kreuder will present the group's findings on May 11 at the annual meeting of the International Association of Aquatic Animal Medicine in Waikaloa, Hawaii. The analysis is expected to be published this year in the Journal of Wildlife Disease.

On May 12, the spring otter count begins, led by the U.S. Fish and Wildlife Service.

The UC Davis Wildlife Health Center, a program of the School of Veterinary Medicine, has a longstanding sea-otter research program in collaboration with state, federal and local agencies. Research projects include studies of survival rates, disease and death; effects of oil exposure; and evaluating the accuracy of aerial censusing.

###

The University of California is one of the world's foremost research and teaching institutions, and UC Davis is the University of California's flagship campus for environmental studies. UC Davis is a global leader in environmental studies relating to air and water pollution; water and land use; agricultural practices; endangered species management; invasive plants and animals; climate change; resource economics; information technology; and human society and culture. One in six of UC Davis' 1,500 faculty members specializes in an environment-related subject.


Story Source:

The above story is based on materials provided by University Of California - Davis. Note: Materials may be edited for content and length.


Cite This Page:

University Of California - Davis. "Troubling News About Sea Otter Deaths." ScienceDaily. ScienceDaily, 8 May 2003. <www.sciencedaily.com/releases/2003/05/030507080349.htm>.
University Of California - Davis. (2003, May 8). Troubling News About Sea Otter Deaths. ScienceDaily. Retrieved November 27, 2014 from www.sciencedaily.com/releases/2003/05/030507080349.htm
University Of California - Davis. "Troubling News About Sea Otter Deaths." ScienceDaily. www.sciencedaily.com/releases/2003/05/030507080349.htm (accessed November 27, 2014).

Share This


More From ScienceDaily



More Plants & Animals News

Thursday, November 27, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

New Dinosaur Species Found in Museum Collection

New Dinosaur Species Found in Museum Collection

Reuters - Innovations Video Online (Nov. 27, 2014) A British palaeontologist has discovered a new species of dinosaur while studying fossils in a Canadian museum. Pentaceratops aquilonius was related to Triceratops and lived at the end of the Cretaceous Period, around 75 million years ago. Jim Drury has more. Video provided by Reuters
Powered by NewsLook.com
Classic Hollywood Memorabilia Goes Under the Hammer

Classic Hollywood Memorabilia Goes Under the Hammer

Reuters - Entertainment Video Online (Nov. 26, 2014) The iconic piano from "Casablanca" and the Cowardly Lion suit from "The Wizard of Oz" fetch millions at auction. Sara Hemrajani reports. Video provided by Reuters
Powered by NewsLook.com
Pet Dogs to Be Used in Anti-Ageing Trial

Pet Dogs to Be Used in Anti-Ageing Trial

Reuters - Innovations Video Online (Nov. 26, 2014) Researchers in the United States are preparing to discover whether a drug commonly used in human organ transplants can extend the lifespan and health quality of pet dogs. Video provided by Reuters
Powered by NewsLook.com
From Popcorn To Vending Snacks: FDA Ups Calorie Count Rules

From Popcorn To Vending Snacks: FDA Ups Calorie Count Rules

Newsy (Nov. 25, 2014) The US FDA is announcing new calorie rules on Tuesday that will require everywhere from theaters to vending machines to include calorie counts. 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