Friday, August 3, 2012

California Sea Lions


California Sea Lion in Newport, Oregon

Tomorrow I get to do my first shift as a bay front docent!  There are some California Sea Lions who hang out below one of the docks at the bay here, so the powers that be (which includes many organizations here in Newport) decided to put a docent there to interpret for people.  (In case you're not in on museum lingo-  as I wasn't until somewhat recently- a docent is a person who interprets, and interpreting in this sense is basically talking to people and teaching them stuff in an informal learning setting.)

I will actually need to interpret to people about many things in addition to the sea lions.  We had a great training on Tuesday that also covered seals, whales, seabirds, boats, fishing, and what goes on with the port here.  But, since people go there to see the sea lions I figured I better know them really well, so I've been spending the day learning more about them.  So here ya go!

Awesome fact sheet about California Sea Lions by Dolphin Research Center.  Much information in this post is paraphrased from there.

California Sea Lions
Live from SE Alaska to central Mexico
Population of about 350,000
Swim with their front flippers and steer with the back
National Geographic
Anatomy
  • Males- larger, up to 10 feet long and 1,000 pounds.  Have a sagittal crest on their heads when about 10 years old, dark chocolate brown color
  • Females- up to 6 feet long and 220 pounds, light brown color
  • External pinnate ears.  The family name means "little ears"
  • Sacral vertebrae are not fused, making them extremely flexible
  • Eyes - they have a tapedum lucidum (reflective material in the retina which helps them see in the dark - same as with cats and many other animals)
  • Eyes - also have a nictitating membrane which is the "third eyelid" that blinks horizontally and is a protector for the eye.  Some marine mammals and fish (ie sharks) have this to protect them while in the water.  For the sea lion, however, it serves to clear away sand and debris when on land.
  • Teeth- they have 34-38 teeth which are used for tearing prey but not chewing (they swallow their food whole)
  • Nostrils- Naturally remain closed.  Muscle action is required to open them.
  • Inner ear- have cavernous tissue inside which scientists think may help them hear better when in deep water
  • They have toenails!  I had no idea.  There are 3 nails on each back flipper.
I can't copy it but this is a really cool picture on flicker of a sea lion scratiching its head and you can see the nails and it also shows the incredible flexibility.


Physiology
  • Amazing blood shunting ability - they can control where their blood goes in the body which is very helpful for thermo-regulation and oxygen conservation.
  • They conserve oxygen really well so they can dive (which they can do for 8-15 minutes).  Their lungs are only about the same size as ours.  But they can shunt blood away from non-vital organs to allow the oxygen to be where it needs to be.  They also have myoglobin which binds oxygen and is an extra storage in the muscles.
  • Blubber- serves as insulation, buoyancy, protection from injury, and food and water storage.  Males who fast through the mating season get all the water they need from the breakdown of the blubber they have built up.
Behavior
  • Distinctive bark - if you hear the sea lion bark, it's a California sea lion.
  • Eat 5-8% of their body weight per day (15-35 pounds of food).
  • Swim 11-25 miles per hour
  • Live about 20 years
  • "Shark imitation" - putting flipper up out of the water is to regulate their temperature.  They can shunt blood to the flipper, getting more blood closer to the body's surface where heat can easily escape.
California Sea Lion in Yaquina Bay, Newport, sticking up its pectoral flipper
 
Reproduction
  • Breeding season is about June- July, and stars just a couple weeks after the females give birth
  • Males stake out a territory for breeding season.  The oldest, biggest, and strongest males are able to hold the territory.  If there is a dispute, the males go through some ritualistic displays to try to scare the other one off.  They will also bluff and charge, but try to avoid bloodshed if they can.
  • Males bulk up before hand, eating as much as they can, then live off the blubber layer.  The longer they can hold out without eating, the more chance they'll get to mate with a female (or many females).  They have harems of an average of 16 females.
  • Females can move in and out of male territories freely
  • Females can delay implantation of the embryo up to 3 months after mating, then they are pregnant for about 9 months.  The poor cows (yes that's what they are called, and males are bulls) are only not pregnant for about a month out of the year.
  • Nursing- as if the pregnancy thing weren't enough, the females nurse their one pup for at least 5 months and up to a year.  Pregnant and nursing...pretty much all the time.
Whew, I did most of that from memory.  At least I will know a good deal about the main attraction tomorrow.  The rest of the information will come with more time, practice, and study.

If you found this useful in any way or have any suggestions please leave a comment by clicking the small comments link! :)  Thanks!

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