Elephant Seals

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Elephant Seals
Named for trunk-like nose of adult males among
the largest of all pinnipeds
Mirounga angustirostris
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Two species

• The term Mirounga is derived from an Australian
  aboriginal name for the elephant seals and
  represents two species in the genus
• Our is the Northern (Mirounga angustirostris)
  from Baja and as far north as Point Reyes on
  shore, but feed up to Alaska.
• angustirostris means having a narrower snout than
  the southern elephant seal
• Southern Elephant (M. leonina) seals are sub-
  Antarctic, and larger then the northern species.
• Both nearly hunted to extinction and now
  recovering

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Adult males (bulls) measure 14-16 ft long can
weigh 4,000- 5,000 lbs
Females are about 1/3 the size of males
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• elephant seals migrate twice a year from CA and
  Mexican beaches to Alaska
• or west to open ocean
• adult males range to Gulf of Alaska
• adult females range as far west as Hawaii
• leave the water twice a year once to molt and
  once to breed give birth at
• the same beaches where they were born!

a tracked males route from Southern CA to the
Aleutian Islands of Alaska
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A males route tracked from Southern CA to the
Aleutian Islands of Alaska
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Breeding
Mating and birthing occur Dec.- March in places
called rookeries
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• in CA, males arrive at beaches in Dec.
• engage in violent battles to establish dominance
• the victor wins mating rights to a harem of
  females
• unlike other seals, which may have harems
  averaging 40 cows, a dominant bull elephant seal
  may have only a dozen cows within his territory.

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Whats with that snout??

• Mostly for vocalizations to defend territory
  and harem
• May Filter
• Helps to condense fresh water from breath

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• Elephant seals do not eat or drink the entire
  time they are at the rookery!
• (Dec- March)
• live off their fat for energy and water
• on land, males can lose as much as 1,500 pounds
• females give birth, nurse, and mate without ever
  eating! --
• she will loose about 40 body weight
• when females leave the rookery in March, they
  are weak and unhealthy-
• immediately swim for the continental shelf to
  search for food

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• delayed implantation
• although mating occurs in Jan/Feb, the
  fertilized egg doesnt implant in
• uterus until May/June after the female has fed
  for several months
• helps to ensure a healthy pregnancy

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• Females arrive in Dec. Jan.- give birth to a
  pup within 6 days of hauling out
• Female nurses pup for about 1 month with milk
  that is 55 fat!

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• Pups weigh approx. 75 lbs. at birth and within
  one month, weigh 250-350 lbs
• Females then leave pups on their own

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some pups sneak off and nurse from multiple
females
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Weaning

• After 1 month, moms abruptly leave pups
• Weaned pups congregate safely in "weaner pods
  for protection.
• Pups fur changes from black to silver
• Pups live off of their fat stores for 8- 12 weeks
  until they get hungry

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Learning to swim and forage

• can't swim at birth
• after weaning, learn to swim by venturing into
  the water for short periods, learning to swim
  and feed
• In late April- pups go to sea and disperse north
  - feed off coast of WA BC

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Molting all at once!

• Have a catastrophic molt loose all fur and
  outer skin layer
• On land warm blood circulate to skin, in cold
  water skin has little blood flow

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Female Maturity

• Females give birth for the first time at an
  average age of 3-4
• Females have an average life expectancy of about
  20 years.

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Male Maturity

• Males are mature at five years
• Males don't reach high rank until 8 with prime
  breeding years between 9-12.
• Males have a life expectancy of 14 years.

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Males

• The older males develop a "cornified chest" - a
  thick calloused skin on the chest with numerous
  creases that is often pink, white and brown in
  color.
• It is used in the fights for dominance and
  establishing territories and harems.
• The enlarged proboscis begins to form at sexual
  maturity about five years and it is fully
  developed by age seven to nine years

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• around the 19th day of lactation, female goes
  into estrus (receptive to mating)
• the dominant bull mates with all females in his
  harem
• while the alpha bull is busy mating, defending
  the harem, or sleeping, other
• bulls (sneaker males) will try to sneak in
  and mate with some females

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Summer molting

• Return to same beaches in summer for a month-
  called hauling out
• With out skin, fur they can not enter the water
  or they get too cold.
• Dont eat or drink for the month they grow new
  skin
• Other seal molt, but only the elephant and monk
  seals have a catastrophic molt.

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Dates vary by group

• Año Nuevo Molting
• April to May for females and juveniles
• May to June, sub-adult males
• July to August, adult males.

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Año Nuevo

• The first elephant seals on Año Nuevo Island were
  sighted in 1955, and the first pup was born there
  in 1961. In 1978, 872 were born there. Males
  began to haul out on the mainland in 1965. A pup
  born in January 1975 was the first known mainland
  birth of a northern elephant seal at Año Nuevo
  86 pups were born there in 1978. By 1988/1989,
  about 2,000 elephant seals came ashore at Año
  Nuevo, and the number of seals breeding and
  giving birth on the mainland is still increasing.
  During the 1994-95 breeding season, approximately
  2,000 pups were born on the mainland. - from
  park website

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Dives

• Elephant seals dive longer and deeper than most
  other marine mammals
• Dive for food- mostly squid, rays, skates, crabs
  ( minimize predation..)
• At sea, spend 80-95 of their time in dives
• may even sleep while diving below predators
• Average dive time 20 minutes-- can be 1- 2
  hours
• Dives are typically 300 - 1500 ft. deepest
  recorded 5,015 in 1991

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Deep Dives

• Avoid predators great white sharks, Orcas
• Deep water food is concentrated at these depths
• Even most of the whales cant get at the food
  source this deep little competition.
• Allowed for speedy recovery?
• Shorter life span- crushing physiology

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Ranging feeding differences between sexes
FEMALES

• range west to open ocean
• ranges more variable than males- pursuing moving
  prey
• dive profiles are jagged- show females are
  following swimming prey (squid)

MALES

• range north along continental margin to Alaska
• range routes highly consistent
• dive profiles are flat-bottomed feeding off
  sea floor (skates, rays, ratfish)

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Dive physiology
heart rate drops by 65 (110 ? 40 beats per min)
(also on land - 30)
metabolism slows
high hemoglobin, myoglobin holds large amounts of
O2
as they dive, exhale to collapse lungs
decreases chance of nitrogen entering
bloodstream which could cause bends when
dissolved gas out of solution
bloodstream carries oxygen only to vital organs
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Conservation Status

• hundreds of thousands of northern elephant seals
  once inhabited Pacific Ocean
• from mid-1800s to the early 1900s, elephant
  seals were hunted for blubber (oil )
• by 1890, only 50-100 seals remained
• only remaining colony was on the Guadalupe
  Island (Baja California)
• 1922, Mexican govt gave protected status to
  elephant seals- U.S. followed suit
• elephant seals have continued to multiply
  exponentially have extended breeding
• range as far north as Point Reyes
• today ? approx. 160,000 northern elephant seals

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• http//www.biosbcc.net/ocean/marinesci/05nekton/es
  body.htm