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Photo: fur seals

The Cape fur seal is a top predator in the marine environment off the coast of South Africa. Photos: Dan Costa

July 17, 2006

UCSC researchers use new technology to study Cape fur seals in South Africa

By Tim Stephens

Sophisticated electronic tagging technology developed as part of the Tagging of Pacific Pelagics (TOPP) program is now being deployed to study Cape fur seals in South Africa.

Photo: seal with electronic tag
The electronic tags are attached harmlessly to the seals' fur and fall off when the seals molt or are removed by researchers.

Daniel Costa, professor of ecology and evolutionary biology at UCSC, is currently in South Africa working with an international team of investigators to study the biology and feeding behavior of the Cape fur seal, the most important marine predator in the region.

"The point of this collaboration is to share new technologies and approaches that have been developed in association with the TOPP program," said Costa, a TOPP principal investigator overseeing the program's research on marine mammals and seabirds throughout the North Pacific.

In South Africa, Costa is working with John Arnould from Deakin University in Australia and Herman Oosthuizen and his colleagues from the Marine and Coastal Management unit of the Department of Environmental Affairs and Tourism in Cape Town, South Africa. The team traveled to a fur seal colony on the northwest coast of South Africa to conduct the study. The colony happens to be located in the middle of a diamond mine, which meant the researchers had to pass through stringent security to gain access to the site.

To understand the habitat needs of the Cape fur seal, the researchers want to find out where the seals feed and how much they eat. The Cape fur seal is currently one of the most abundant fur seals in the world. Researchers and conservationists would like to better understand the role of this top predator in the marine environment, and they would also like to make sure that appropriate protection is in place to assure that the population stays healthy.

"Our efforts are aimed at helping our South Africa colleagues understand the biology of this amazing animal before its population starts to get in trouble," Costa said. "We've seen many populations of sea lions and fur seals throughout the world become endangered or threatened. In South Africa, not only can we study an animal whose population is healthy, but we can lay the groundwork for conservation and management before there is a crisis."

With the support of a grant from the National Oceanographic Partnership Program, Costa and his collaborators have developed new tracking devices that use the Global Positioning System (GPS). These GPS tags allow researchers to follow the movements of marine mammals to within 30 feet of their real position. Previous tracking technology using ARGOS satellites could only give locations to within 500 feet, at best, and when used on seals at sea was usually only good to within a half mile or worse, Costa said.

In addition to the tracking technology, Arnould is deploying stomach-temperature telemetry tags that record when the animals consume prey such as fish or squid. This is based on the idea that seals, as warm-blooded animals, have an internal body temperature higher than the temperature of their environment, and when they eat a fish that is the same temperature as the water their stomach temperature declines. UCSC graduate student Carey Kuhn recently validated this technique for use on sea lions and seals for her dissertation research, with support from TOPP and California Sea Grant.

The team is also interested in how hard the seals are working when they are at sea. They have deployed special heart-rate sensors that will record the seals' heart rates during swimming, diving, and other activities. This technology is based on the same heart-rate sensors that joggers and athletes use.

The oceanographic conditions off the west coast of South Africa are very similar to those off the California coast, which makes the area of particular interest to TOPP researchers, Costa said. In both locations, a cold-water current flows toward the equator, and winds cause nutrient-rich upwelling.

"These regions are ecologically very similar, with abundant marine mammals and seabirds, and they are among the most productive waters in the world for commercial fisheries," Costa said.

For more information on TOPP, visit the program's award-winning web site.

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