Thursday, May 5, 2016

Tagging seals for research

There’s always something different to see at the elephant seal viewpoint. Beachwalker Elizabeth Bettenhausen spotted this marked seal at Arroyo Laguna beach in April. Her sighting became part of Patrick Robinson’s research.
Dr. Robinson, UC Año Nuevo Island Reserve Director and UC Santa Cruz lecturer, has marked hundreds of flipper-tagged animals each year. The markings make it easier to identify them from a distance, without disturbing them. Or, incidentally, putting the observer at any risk. Watch how Dr. Robinson marks the seals in this video.

“We marked this seal up at Ano Nuevo a few months ago and it appears to have returned home,” he said. “I'll incorporate this sighting in our database.  Many thanks!”

His research is discovering where seals go, and identifying which seals are on local beaches. This seal is in a general demographic study.

The dyed markings are temporary. They will peel off with her skin when she molts, which is happening in April and May.

Elephant seals molt their skin annually in the spring. All other seals molt, but most do so gradually, so it isn’t as noticeable. Molting seals show pearl gray new skin underneath the tattered old brown skin, peeling back.

The new skin is already formed beneath the old skin. Blood gradually stops flowing to the old skin, and it peels off in pieces. Friends of the Elephant Seals docents have samples of it to show visitors. Visitors are welcome to touch it, feel its bristly hairs. Some visitors are reluctant, but most are willing.

Some of the seals have a color-coded tag on their hind flippers that indicates where they were born. About three quarters of the seals return to their birth beach. About ten percent of Piedras Blancas seal pups get a white tag. All colors of tags show up here. The tags are small, only an inch and a half long, and can’t be seen when the flippers are folded, as they usually are when the seals are at rest. Look for a seal stretching its flippers to see a white, red (San Nicolas Island,) yellow (San Miguel Island), pink (Farallones Islands and Point Reyes), purple (Gorda) or green (Ano Nuevo) tag.
This seal got two white tags.
This yellow tag indicates the seal was born on San Miguel Island.
Markings and tags allow researchers to glean information about where the seals go and what they are doing there. Citizen scientists who see markings help by reporting sightings.

Elephant seals are deep divers, spending their days at 500 to 2,000 feet down in the ocean. That makes them difficult for fragile humans to follow. We’d be crushed at the pressure, more than 60 times the atmosphere on the surface. Humans experience serious effects at 100 feet, and even professional free divers don’t go past 400 feet. Digital tracking equipment opens opportunities that would otherwise be beyond human observation.

Tell a blue-jacketed docent if you observe unusual markings. Be part of the adventure of elephant seals.
Published in The Cambrian.