Año Nuevo (8/5/04)         

Karen Pihl

(Image: Northern elephant seal)

What to Bring.

You will need money to park ($5.00) and to cross the San Mateo Bridge ($3 .00).

No food is available.  Half Moon Bay is the last place to get food.

It takes two hours to get there from here.

Where to Go.

Año Nuevo

Año Nuevo = new year

Ohlone Indians came here.

Buildings are the remains of a dairy.

Fields were used  for brussel sprouts.

San Gregorio Fault runs through it.

Marine Mammals

Found at Año Nuevo at various times of the year or present year round

Classification

Humans attempt to organize the natural world by imposing a classification system on it.

Organism are grouped into domains, kingdoms, phyla, classes, orders, families and genera.

The genus is the least inclusive category.

Pinnipeds.
Order Pinnipedia

Streamlined, large eyes, flippers.

Sea lions and fur seals.  Family Otariidae.

Harbor seals and elephant seals.  Family Phocidae.

Northern Elephant Seals

Female, 10-12 feet, 2000 lbs.

Male, 14-16 feet, 6000 lbs. (Image: Male Northern Elephant Seal)

Life span - 14 years for males, 20 for females.

Formerly bred from Baja to Pt. Reyes.

Hunted for oil - 210 gallons of high quality oil from one bull.

Recovery

1892, Smithsonian found 9, killed 7.

Island of Guadalupe (off Baja), less than 100 survived.

Now approximately 160,000.

1955, first seen on Año Nuevo Island.

Now breed as far north as Pt. Reyes.

Behavior

Dominance hierarchy - most aggressive (alpha) male mates with the most females.  (Image: mating male and female seals)

4% of males inseminate 85% of the females.

Males arrive in December at Año Nuevo.

Females arrive several weeks later (January) and give birth to pups that were conceived the previous year.  Only one pup is born per female.

Nurse 3-4 weeks.  Milk is 55% fat.  (Cow's milk is 4%.)

Female breeds (about 24 days after birth) and leaves.

Delayed implantation of embryo.  Allows female to regain weight before fetus starts to grow.

Pup grows from 75 lbs to 250-350 lbs when weaned.

Pup born the following year in January.

Males demonstrate very aggressive behavior.

Guard females and move with them along the beach.

Chase away males that approach harem.

May crush pups while defending harem.

Subordinate males attempt to mate with females as they return to the sea and even with weaned pups ("weaners"), dead adults, yearlings and subadult males.

Adults leave in March-April.

Young stay until April-May.

Spend most of the year at sea alone.

One male went from San Miguel Island off Santa Barbara to Alaska  twice in one year.

Young seals are born with dark hair which absorbs heat and helps to keep the pups warm.  They lose this at about one month and become silvery brown. (Image: young pup)

Adults molt in spring, summer.

Molt is catastrophic.  They lose large patches of skin and hair.

Swim using pelvic muscles and rear flippers.  Front flippers are kept close to body.

Can dive over 4000 ft.  Depth gauges have been attached to seals.

Dive day and night, nonstop. 

Eat squid, skates, rays, rat fish, small sharks.

Swallow prey whole.

Have carnivore teeth.  Look at the skull on display.

Deep feeding may explain recovery from near extinction.  Few predators or competitors for food.

Have 2 1/2 times blood of humans relative to weight and a high red blood cell density.

Great oxygen storing capacity.

Exhale before diving.

Heart rate slows.

Sexual Dimorphism

Males and females have a different appearance.

Males have proboscis. 

Large chest shield protects male from bites by other males. (Image: male seal, showing large chest)

Females are smaller.

Enemies

Sharks and killer whales.  Great white sharks are found off Año Nuevo.

Thermoregulation

Temperature regulation.

Blubber for insulation.  Hair does not insulate well at depth.

Shunt blood away from body surface when swimming.  On land, blood is circulated to the skin to radiate heat to the air.

Coat themselves with sand. (Image: seal coating itself with sand)

Pups

Crushed by males defending harem.  Attacked by females. Drown.

Starve if separated from mother.

Gather in "weaner pods" possibly for protection from males after being weaned.

Some steal milk and some are adopted by another mother to become "superweaners" who may weigh 600 lbs.

Learn to swim and what to eat on their own.

A "weaner" is shown below. (Image: a "weaner" pup)

The concern...

All are descended from less than 100 individuals.

The population lacks genetic diversity.

Lower ability to survive changes in the environment.

Assignment:

Visit the Año Nuevo State Reserve web site and read the sections on elephant seals and marine life. Look under "related links"

Año Nuevo State Reserve web site (Image: Tracks left in the sand by an elephant seal)