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.

 

Monday, March 14, 2016

Weaners take over the beach

In March, the uproar of breeding season is past. Weaners have the run of the beach.
The rain we had generated large amounts of runoff from the ranchlands across the highway. But the weaners are grown up enough now that they aren't in any danger. They used the stream for breath-holding practice.
One had trouble climbing out. as he lurched up the sandy side, it collapsed under him.

 He finally moved to a section where the bank was shorter and was able to climb out. Another weaner took an interest.

 
 

Thursday, February 25, 2016

Peace on the beach

Breeding season is winding down, and the beach is much calmer. Dominant males are still being challenged by other males, but the level of energy is lower. They care, but not as much. Everyone is tired.

Weaner pups are molting their birth black coats. It's more like shedding than the actual skin peeling off that comes later in life.
Males mate as they can with females before they leave on the next stage of their migration.
We've had some high tides and big waves, but the weaners are able to navigate the beach away from high water. Soon the adults will be gone and they will have the beach to themselves.

Wednesday, February 3, 2016

Pups at high tide


Plenty of pups squirm on the beach in January, under the watchful eyes of their mothers. The bulls are less concerned, with their attention focused on mating. This year’s high tides and storms have added to the chaos.
Elephant seal pups can’t swim when they are born. That inability must be a holdover from their evolutionary past, when their ancestors were land mammals. As helpless pups, they are at risk of drowning as waves inundate the beach.

At Piedras Blancas this year, there’s almost no beach above high tide line at the north end of the boardwalk. Seals have crowded up next to the fence to stay above the water. Visitors are thrilled to get such a close look. But bulls battling each other and mothers shoving each other for space can separate mothers and pups, and make it difficult for them to reconnect. One docent counted 21 pups in a group that included only 14 possible mothers last week.
In the limited space left to mothers and pups, they crowded together to stay out of the waves. Look for mothers surrounded by three or four pups. Elephant seals give birth only to a single pup. Twins are unknown. Mothers don’t eat for that month while they are nursing the pup. They create milk by metabolizing their blubber. Each seal is plump enough to feed one pup, but not more. Any extra drains her resources further. 

Losing track of each other is serious, the single most common cause of pup death. Some mothers will nurse other pups, but other chase them away. Inexperienced mothers may learn from mothering other pups, but the milk they drink may deprive her own pup of the food he needs to grow. Some mothers are willing to foster a pup for a few days. Mothers whose pups die may adopt a stray, or even attempt to steal a pup from another mother.

Last week, one mother searched for her pup as the tide receded. Mothers and pups identify each other by sound and scent. She sniffed around, and barked occasionally. Pups around her slept on, but she likely reconnected with her little one before the tide returned. About 95 percent of the pups at Piedras Blancas survive to weaning.

The south end of the beach has more dry land for pups, so there’s less confusion there. Watch for the dominant bulls, beachmasters, to defend their harems. That big seal with a long nose may appear to be asleep, but he knows is some younger interloper tries to approach a female. He’ll warn the intruder off with a look and a bellow. If that’s doesn’t work, he’ll rise up and wave his nose. He’ll charge and attack the younger bull, who may escape or turn to fight.

Read the column in The Cambrian.

Tuesday, December 15, 2015

Pup season

Two more pups had been born as of December 14. The tides are very high, putting them in danger. Even higher 'king' tides are forecast for December 21, 22 and 23 next week. It's good that the pup season is only beginning and the beach is not yet too crowded.
Fortunately, this mother was staying on the ocean side of her pup. This is the first pup born. He's already very fat, so in less danger than a newborn.
There are three pups in this group, with several other mothers-to-be awaiting birth. This group is on the south section, about halfway out on the boardwalk. The senior male is a calm influence. No less dominant males dared to harass the mothers under his protection.

Tuesday, December 8, 2015

Seals eat hagfish


From this month's column in The Cambrian:


Elephant seals hunt at 1,000 feet and deeper. Digital tracking devices make it possible for us to know this, but much of their feeding behavior remains unknown. It’s too dark down that far for a critter cam to function. One seal was tracked over 17 hours of her day. Most of her dives were 20 to 30 minutes long, down to between 1,500 and 2,500 feet. One dive of over an hour brought her to around 4,000 feet.

Knowing where they go lets us infer that they are eating the fish and squid that live there. One remarkable video did catch a female elephant seal eating a hagfish. It was part of a study by Ocean Networks Canada, which placed a pod at about 3,000 feet deep. The lights and camera went on to record video for 15 minutes in every two-hour period.

It recorded a huge amount of video, so the word went out to citizen scientists worldwide to watch the video and report interesting events recorded. A dedicated 14-year-old boy in the Ukraine watched long enough to see a female elephant seal slurp up a hagfish

Hagfish are living fossils, unchanged over 300 million years. They are primitive fish, with no jaw. Instead, their teeth flex out from inside their lips. They travel in schools, feeding on the ocean bottom, eating worms and carcasses of dead animals that float down.

Eating a hagfish is more difficult than she makes it look. When they are threatened, hagfish nearly instantaneously cover themselves with sticky, gooey slime. [Do the Ghostbusters know about this?] It’s so thick and viscous that sharks have to spit them out. The slime clogs their mouths, making it impossible for them to breathe in water. Elephant seals, even if they took longer to eat a hagfish and it bloomed its slime protection, could eat them anyway. They breathe at the surface, so no problem for them.

Improvements in digital technology will undoubtedly advance so that we can know more about what and how elephant seals eat. For now, we can be confident that those huge seals resting on the beach represent lots of food consumed.

Adult males will arrive in December, preparing for the breeding season to come in January.

Friday, December 4, 2015

First pup!

The first pup of the 2015-16 breeding season was born November 28. Mother and pup are doing fine.

These photos were taken when he/she was two days old. He looks like he's already filling out.

The first birth is usually in late December, but occasionally pups are born earlier. Sometimes they are not healthy and don't survive, but this one is doing fine.