Pups wean to independence
Adult seals breed for next year’s pups
Many mothers have weaned their pups, who now rest in
groups (pods) at the base of the bluff. They’re staying clear of the ruckus of
breeding among the females who are still nursing and preparing for their short
migration.
The mothers come into heat as nursing concludes. Bulls
vie for breeding rights, sometimes coming to blows.
Beachmaster imposes discipline
The beachmaster, usually the biggest bull, rules the
females in his section of the beach. Less dominant males are constantly looking
for opportunities to breed females at the edge of the beachmaster’s influence.
The dominance hierarchy helps reduce actual fighting. Bulls recognize each
other’s unique vocalization, as if each one had a name. Bulls who have fought
in the past don’t have to fight again to establish who is boss.
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Weaners face the world
Pups are born with black coats, which help keep them
warm. Being born on the California coast in December and January makes that
important for pups who have little blubber when they are born. In that month of
nursing, they gain about 200 pounds. Nicely rounded now in blubber, the pups
molt their black coats for their first brown and tan coat. After molting, they
are countershaded darker on their backs and lighter on their bellies, a form of
ocean camouflage.
Weaned pups have to learn to hold their breath, swim
and dive before they leave the beach on their first migration. At sea, they
will have to learn what to eat and how to catch it. The PBS program Animals
With Cameras documented how they practice.
Wildlife cameraman Gordon Buchanan, who narrates with a Scottish brogue, worked with Ano Nuevo researchers Patrick Robinson, director of the Ano Nuevo Reserve, and Roxanne Beltran, assistant professor of ecology & evolutionary biology at UC Santa Cruz, to equip four weaners with cameras to record 16 hours in their lives. Watch the results at the 44-minute mark.
The cameras revealed unexpected behavior. Under water,
the weaners interacted with each other more than the scientists’ expected.
“I’m surprised by how active and interactive they
are,” Dr. Robinson says, as the seals cavort in their watery home. “They’re
completely solitary at sea,” says Dr. Beltran. “So the fact that these guys are
interacting with each other is weird. I wonder if they are just learning from
each other.”
The video shows that the weaners hold their breath on
land as well as in the water. Eventually, they will hold their breath for 15-20
minutes on each dive to feed. The video records one pup holding his breath for almost
12 minutes.
“It doesn’t look like they are doing much here,” says
Dr. Beltran, “but I think what they are actually doing is figuring out how to
become breathless divers, so that they can find food on their first trip to
sea. Just like we would train for a marathon by doing little runs, they’re
doing little breath holds to basically figure out how they can get down to food
on breath holds.”
The weaned pups are living on their blubber until they
depart on their first migration. That blubber makes them buoyant in the water,
though. The pups have to work to dive, and seem to help each other stay down.
The video shows them chasing fish, although they don’t
catch and eat any. It also shows them playing with plastic trash and kelp. Play
is important to young animals’ development.
“In these seals, it may help build those important
diving skills, that later they’ll rely on,” says Buchanan.
Glimpsing the seals’ life underwater is thrilling. I
watched it over and over. The entire show includes video from loggerhead
turtles, tiger sharks, and gannets.
Buchanan calls the elephant seals “elite ocean
divers.” Dr. Robinson observes, as they swim underwater, “They’re more graceful
than I thought, based on how they are on land.”