The Cambrian

Elephant seal news: Female seal’s remarkable stats

Friends of the Elephant Seal has received a report on the data gleaned from equipment on a female elephant seal that visited the Piedras Blancas rookery on May 12.

A team of researchers from UC Santa Cruz came to the beach and retrieved the time-depth recorder and a sensor that measured oceanographic information.

It turns out that she was quite a remarkable seal, making a dive to 1,180 meters (about 3,871 feet, nearly ¾ of a mile) lasting more than 71 minutes. This is a much deeper and longer dive than average. The rest of the time she was diving in the 1,000- to 2,000-foot range.

The data also showed that she foraged up off the northern Canada coast and ventured near some seamounts up there.

While she was here on the beach, the researchers sedated the seal and, in addition to removing the global positioning system (GPS) unit, about the size of a wallet, glued to her head, took blood, and did ultrasound to determine the depth of her blubber.

That data was compared to similar data recorded before she left the Año Nuevo area near UC Santa Cruz in February after her winter fast. The blubber depth, which was 5 to 6 inches, indicated how much weight she had gained while foraging successfully on her migration route.

They also weighed her by placing her on a tarp, which they winched up on poles, weighing it and deducting the weight of the tarp. She weighed 900 pounds. A female elephant seal can weigh as much as 1,800 pounds, still much less than a male, which can reach 5,000 pounds. It’s easy to understand why most of the studies are done on females, which are much easier to handle, although they do put GPS units on some males. The males do most of their foraging in the Aleutian Islands in Alaska, a journey they make twice a year.

The studies, reported to Friends of the Elephant seal by Dr. Patrick W. Robinson at UC Santa Cruz, are being done by Dan Costa’s laboratory there, which is doing a long-term tracking study of northern elephant seals at Año Nuevo State Reserve. Some of those seals sometime visit us at Piedras Blancas. Graduate students and collaborators are investigating topics such as “habitat use, foraging ecology, fine scale behavior, toxin loading, diving physiology, climate change, and ontogeny,” according to the lab’s website.

Tracking data is available to the public at www.seaturtle.org. Elephant seal tracking can be seen at http://www.seaturtle.org/tracking/?project_id=573&id=592.

Friends of the Elephant Seal is presenting more research information in a free talk by Dr. Gregor Caillet at 1:30 p.m. Saturday, July 30, at Rabobank, 1070 Main St., Cambria.

He will talk about “Life Histories and Fishery Ecology of California Sharks and Rays — or, Unraveling the Secret Lives of Sharks and Rays.” He will discuss the diversity of sharks and rays both worldwide and off California, list their major adaptations, discuss studies of their life histories (age, growth, reproduction, demography, feeding, etc.), the status of their populations especially as that relates to fisheries and management measures that can be used to more effectively control their fisheries.

This will include a brief discussion of the shark-finning issue. He will also relate some things about the ecology of white sharks, especially as it might pertain to the Elephant Seal rookery here.

Joan Crowder is a volunteer docent for Central Coast Friends of the Elephant Seal. For more information, call 924-1628 or visit www.elephantseal.org.

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