Tagging of Elephant Seals
The TOPP E Seal Team from Dr. Dan Costa’s Lab at Long Marine Laboratories at UC Santa Cruz studies elephant seals using two types of tagging. Both forms are highly influential in gaining an understanding of elephant seal population dynamics, behavior, distribution, foraging, migration, you name it!
Each year as the breeding season comes to an end, up and down the coasts of California, biologists are venturing out to the harems to attach flipper tags to pups as they are weaned. A biologist attaches a plastic tag with an identification number to the hind flipper of the animal. This is done by sneaking up on the animal while it’s sleeping and inserting the tag before it wakes up. Biologists can run away before the weanling notices it’s wearing a new tag. These handy tags are used to track individuals and populations over time. The colonies in California in which flipper tags are attached to elephant seal pups are: Piedras Blancas (white), Ano Nuevo (green), Point Reyes (pink), San Nicholas Island (red), San Miguel (yellow) and the Farallones Island (pink).
The flipper-tagging studies rely on biologists and docents from the colonies to keep track of individuals. They patrol the beaches to read the flipper tags on animals. That’s easier said than done! Imagine a 10-foot long elephant seal wearing a flipper tag less than two inches long! Needless to say, binoculars, scopes or telephoto lenses are required!
Flipper tags from San Miguel and San Nicholas Islands
The second type of tags are satellite tags. Tagging of Pacific Pelagics (TOPP) began in 2000 as one of 17 projects of the Census of Marine Life, an ambitious 10-year, 80-nation endeavor to assess and explain the diversity and abundance of life in the oceans, and where that life has lived, is living, and will live. Several dozen TOPP researchers from eight countries began venturing into offshore waters, remote islands, and along rugged coastlines to attach satellite tags to 22 different species of top predators that roam the Pacific Ocean. As of 2007, they have tagged more than 2,000 animals, including elephant seals, white sharks, leatherback turtles, squid, albatross and sooty shearwaters.
Elephant seals are an excellent species to study because they return to the same harems year after year, travel across the oceans allowing TOPP to learn about a wide variety of oceanic ecosystems, are robust and successful foragers, they have a 30-year dataset from flipper tags, and they are top predators.
Northern elephant seals dive deep, routinely to 1,800 feet (600 meters), sometimes to 4,650 feet (1,550 meters). Elephant seals are one of TOPP's star animals. They spend 10 months a year at sea, so they bring back lots of data. They're so large that a couple of robust satellite tags weighing two pounds makes up a mere one to two tenths of a percent of a female seal's weight. That's a small pack of gum to a 150-pound human. And because they usually return to the same beach a couple of times a year, it's easy to attach and remove the tags (except when they return to Piedras Blancas).
Since 1983, when elephant seals first carried depth recorders, they've been central to the development of a variety of tags that:
We can marry elephant seals' migration tracks with satellite information about the ocean. We see males heading way out to sea and diving deep to find food, while females seem to linger around ocean "hot spots" -- slowly moving eddies where there's a lot of life (and hence a lot of grazing and feeding).
Below are two of TOPP’s featured E Seals from last the 2008 Elephant Seal Homecoming Days. Both Cheddar and Myoceen were tagged at Año Nuevo State Reserve by TOPP, but returned to Piedras Blancas to breed.
was very close to Año Nuevo, bouncing between 9 and 20 miles from the colony. Cheddar is a 10-year-old seal, born at Año Nuevo State Reserve. She is remarkably close to Año but hasn't come up on the beach! This is odd behavior because elephant seals usually stay out at sea until they “commute” back to their colonies to breed and pup or molt. Cheddar spent weeks taking a slow swim down the California coast and then passed Año Nuevo. Cheddar then swam around Santa Cruz near the Monterey Bay! We don't know why, but it seems strange that she lingered within a mile of Long Marine Lab, home of the Costa Lab's elephant seal tagging program. Just after she decided to head back out to the open seas, Cheddar took a steep turn south and hauled out at the Piedras Blancas breeding colony near San Simeon in California.
Myoceen, a 15-year-old seal also born at Año Nuevo, was on her way back to Año when she, too, continued south! Researchers were worried that she would decide to have her pup in on one of California's remote Channel Islands, but instead Myoceen suddenly turned around and swam back up to Piedras Blancas (see the second track). Myoceen was then watched closely by the Friends of the Elephant Seal docents at Piedras Blancas, and checked on by the E Seal Team. After ten days she had her pup, and after 15 we traveled down the coast to retrieve her tags.
Removing a tag