STELLER SEA LION BIOLOGY
life span & physical characteristics

fast facts | distribution | lifespan | diet | population decline | ​anatomy

Steller sea lions belong to the group of mammals known as pinnipeds (“feather footed”) meaning they have wing-like flippers. Their pelvic bone structure allows sea lions to walk on their four web like flippers. In the water the Steller sea lion pulls itself through the water using its front flippers. They reach speeds of 17 m.p.h. (27 kph). Other marine animals such as seals, swim with their hind flippers using a body action that is more fishlike.

group-steller-sea-lions

Dominant males guard territories on rookeries where they fight for the right to breed

  • Maximum life expectancy is about 18 years for males and 30 years for females.
  • Females produce their first pup between the ages of 3 and 9 years.
  • Mature males begin to breed between the ages of 8 and 10 years.
  • Steller sea lions appear to prefer the coastal shelf region within 45 km of shore, although they can be found over 100 km from shore in waters over 2,000 m deep.
  • Few sea lions are sighted at sea during June and July, the breeding season.
  • Stellers do not undertake extensive migrations like some other pinnipeds.
  • Males may disperse further than females, and tagged subadults have been sighted up to 1,500 km from where they were marked.
      
 Rookeries

Steller sea lion rookeryNot all sea lions return to rookeries each summer. About 45% of the population will use non-breeding sites called haulouts, during summer, and all will use the haulouts during the remainder of the year. There are about 39 major rookeries and over 250 haulout sites in Alaska.

 

listen

LISTEN to the sound of a Steller sea lion rookery

 

Most of the sites are on remote and exposed rocks and islands and are generally believed to be in close proximity to food resources. The females usually mate about two weeks after pupping. Pups are born from late May to early July, with the peak of pupping occurring in June. Sea lions give birth to a single pup in June at rookery sites where large males hold territories and fight off other bulls for the right to breed.
Steller sea lion haulout
Adults and dependent young tend to concentrate on rookery sites until October, dispersing to haulouts for the remainder of the year. Males begin to come ashore at rookeries in mid May, and will remain on land until mid July without eating or drinking. Males hold territories an average of two years. The females arrive shortly after the males and give birth to a single pup within three days of being on land. Females tend to stay with their pups for the first 5-13 days after birth then go to sea to feed. Feeding trips generally last for less than 24 hours and occur every 1-3 days. Pups generally nurse for a year and may stay with their mother for up to three years. There is considerable uncertainty about when sea lion pups are weaned.

Comparison of Male, Female and Young Steller sea lions

Males (Bulls)

  • On average, nose-to-tail length of 3 m and weight about 680 kg (1496 lbs). Weighing up to 1000 kg (2200 lbs); have a thick neck and big chest.
  • Males hold territories for an average of two years.
  • Males defending territory (184K)Males are much larger in appearance and overall size than females.
  • Male Steller sea lions have a thick mane to protect themselves when fighting with other males or from the cold temperatures & from jagged rocks.
  • Males have a higher mortality rate than females, by ten years of age there is a 3:1 ratio of females to males.
  • Males are 1.3 times as long but are 2.5 times as heavy as females.
  • Adult males lose weight & grow little during the breeding season while fasting and grow little during the summer.
  • Adult males gain weight from autumn through early spring in preparation for the breeding season.

 

 

Female Steller sea lion
Females

  • Length of 2.3 m and weigh about 270 kg (594 lbs).
  • Lighter coat than pups.
  • Slimmer neck than males.
  • Arrive at rookeries shortly after the males and give birth to a single pup each year, within three days of being on land.
  • Females usually mate about two weeks after pupping.

 

 

 

Young (pups)

  • Weigh about 20 kg (44 lbs) when born (male pups are usually larger than female pups).
  • videoclpBrown coat.
  • Pups are born from late May to early June.
  • Juvenile animals may also grow very little during the breeding season and summer, with most of their growth occurring from autumn to spring.
  • Pups generally nurse for a year and may stay with their mother for up to three years. There is considerable uncertainty about when sea lion pups are weaned.

Researchers are focusing on Steller sea lions’ feeding patterns and nutrition to help determine if the drop in Steller sea lion numbers has something to do with changes in the food they eat.

 

 

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