Monday, March 19, 2012

Southern Elephant Seals

Claudio Campagna of the Wildlife Conservation Society - Argentina talked about his work with Southern Elephant Seals in Cambria March 17. He and Burney LeBoeuf  are preparing a paper on the issues affecting elephant seal rookeries that have a lot of visitors: Valdes Peininsula, Ano Nuevo and Piedras Blancas.

He gave us information on the differences between Northern and Southern Elephant Seals. He began with a slide showing comparable photos of both: "As you can see, the Southern Elephant Seal is very beautiful, and the Northern Elephant Seal is very ugly," to appreciative laughter.

SES are larger, five meters, 15 feet, but the nose is smaller. Sexual dimorphism is similar, the male five to six times large than the female. Males weigh around six tons. SES females weigh 30-50 pounds more than NES females. They are biologically similar. 

Because the Valdes Peninsula coastline is so much longer, 200 km of beach, seals are often at lower density than the crowded NES beaches. Pup mortality and maternal separation are therefore less common. There are often no peripheral males. In places where the SES are more crowded, they are more like NES. They are polygynous and males have differential access to females.

"I don’t believe that Southern Elephant Seals have twin pups," he said. He also observed that the females don’t adopt the way NES do. "You never see a mother with more than one pup," he said. "Maternal separation is pup death." 

Pups are born weighing around 80 pounds and nurse for 21-23 days. The mothers come back to the beach after two months to molt.

Pups are born in the southern hemisphere spring, August through November. The first week of October is the height of the breeding season. About 16,000 pups are born in the Valdes Peninsula rookery, indicating a total seal population of around 52,000 – 53,000. Growth in the rookery population is considered due to increases in births rather than immigration. The rookery is not receiving individuals from other areas. Its fast growth over the past 20 years appears to be plateauing, suggesting that the rookery is reaching its carrying capacity. It’s the 4th largest in the world. The South Georgia colony is the largest, producing around 100,000 pups annually. 

The Valdes Peninsula rookery is a 20th century rookery. Because SES were not hunted to such a small population as the NES, they have more genetic diversity. Fathers can be identified by DNA tests.

SES cannot be approached the way NES can. The males are very aggressive and will attack and bite. The females will abandon their pups if humans come near. They will return to the ocean.In this picture, Campagna was tagging a seal when he awoke and and complained.

His Patagonian Sea Project was inspired by the elephant seals to expand understanding of what marine conservation is. The idea is to use the elephant seals to tell the story of marine conservation. His focus is on Big Ecosystems and the charismatic wildlife that attracts public attention. By saving the charismatic species, other species and habitat are saved.

"The animals are ambassadors of what is going on in the ocean," he said. "We trust that educated people will change those bad practices."

The Valdes Peninsula is important to the SES because of the ocean currents and configuration of the continental shelf in the area. The coast is like a platform that falls off very deep. As the ocean currents drive water against the underwater cliff, nutrients rise to the surface

"It’s like supermarkets they need to feed the next generation, right near the breeding colony," he said. "It’s predictably producing food to replace what you lost reproducing. Because this is an important area of reproduction, the trip is worth it. It’s almost magical."

The human impact of shrimp, squid and other commercial fishing on the areas through which Southern Elephant Seals swim is substantial. The Atlas of the Patagonian Sea includes maps that illustrate how intense the fishing is.

"These are all important conservation issues," he said. "We have to do much more than make sure the seals are not being disturbed on land. We have to have open ocean conservation."

The Valdes Peininsula where he does his research is one of three mainland rookery sites. The other two are Ano Nuevo and Piedras Blancas. As such, we share some concerns: How do the visitors impact the seals?

The economy at Valdes is changing with the new industry of wildlife spectacle watching. 100,000 tourists come to Patagonia for whale watching, the main attraction. They also see the sea lions and the elephant seals. Park rangers are all professional guides. Tourists have to buy a tour. There is no carrying capacity. Big businesses driven by commercial interest, 70 companies.

"Valdes is not sustainable," he said. "They may have to limit tourists in the future."
At Ano Nuevo, the first female gave birth in 1975. Soon 40,000 tourists were coming to see them. The parks department took over and limited tours. They now get some income from guided tours with professional and docent guides interpreting behavior. Research is being done.

At Piedras Blancas, it’s a different system. PB’s carrying capacity is limited only by the size of the parking lot. Growth will increase. FES provides a critical service with docent presence, ability to call rangers as needed and an organized educational service.

"I am hesitant about Piedras Blancas," he said. "I want to see how you are adapting in five or six years. I reflect that we share the same interest. I encourage you to go farther. See the ocean through the seals’ eyes. What problems do they face, what conservation problems, what fisheries? What is their future?"

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