Monday, February 3, 2014

Northern Elephant Seals at Ano Nuevo

Want to see elephant seals? Head to Ano Nuevo State Park on the Pacific coast between Half Moon Bay and Santa Cruz. Can you guess how elephant seals got their name? (See photo below.) Can you guess how the park got its name? (Spaniards, New Years, 1603.)

From mid-December through March Northern elephant seals come here to give birth, nurse and mate. I took a three-hour docent-led hike 2-3 miles over coarse sand and dunes 30-40 feet tall. Juvenile males frequently rest a mile or more inland while bull seals protect their harems closer to the shore.

This young male unsuccessfully attempted to 'get a little loving' from a loudly objecting female. She'd just given birth to the pup in the foreground. See that sand cloud in the background? Seals cool themselves off by flipping sand on their bodies. (Lots of sand flew the day I visited.)

A female elephant seal rejects the attentions of a young bull after giving birth to the pup in the foreground.
Bull, female and newborn elephant seals

Birds are the surest indicator of birth. They hover in anticipation of the afterbirth. Hey, it's very nutritious. (Yeah, yuck anyway.)

Seagulls fight over the afterbirth of elephant seals. Black newborn seal is in the foreground.
Seagulls signal seal birth

Males come ashore first and carve out territory. When the females arrive, the mature bulls fight to keep others away. This gives the females time to give birth although the pups may not be his. His reward? He gets first chance to impregnate the new mothers.

Why do females put up with this? Elephant seals have the most extreme dimorphism of any mammal. Not only do males develop a distinctive proboscis (nose), they grow to be two or three times as heavy. Successful birthing frequently depends on a dominant, two-ton male fighting off less patient juveniles.

Grizzly skull is significantly larger than the female elephant seal's but the male elephant seal skull is more than twice as large.
Grizzly bear skull on the left compared
with female and male elephant seal skulls on the right.
Grizzlies have molars to chew their food; seals don't.

The females nurse their pups for 28 days then head back to sea to eat and rebuild their fat reserves. (Except pups, no one eats the entire time they are ashore so seals can lose 40-50% of their weight.) They mate before leaving shore but delay impregnation until they regain their weight. Eleven months of pregnancy but only eight months gestation.

Scientists track elephant seal movements, recently even adding transponders near their jaws to determine when and what they eat. (Mainly small fish.) Like moose, the sexes separate after mating with males following the coast north to the Aleutians and females heading straight west as far as the International Date Line. Doesn't she look like she has a headache? I was glad to realize these devices are only temporary.

Dozing in the sand, this light brown female has transponders glued to her head and back which will come off when she molts in the summer.
Transponders glued to this female will come off when she molts in the summer.

Enjoy the day! Ann

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