The Evolution of Sea Otters
What is the Sea Otter?
Species Name: Enhydra lutris Ancient Greek en/εν "in" and hydra/ύδρα "water" meaning "in the water", and the Latin word lutris, meaning "otter"
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Family: Mustelidae
Genus: Enhydra
Species: Enhydra lutris
What is the Sea Otter?
Where did they come from?
The sea otter actually derives from the weasel family!
Natural Selection!
- Dating back over 5 million years ago, there was a shortage of food for Weasels.
- Stuck in environment and couldn't go back to original families.
- Adapted to environment, and continued to survive.
Origin
- Fossil evidence indicates the Enhydra lineage became isolated in the North Pacific approximately 2 MYA.
- Evolved initially in Hokkaido and Russia, then the Aleutian Islands, mainland Alaska, and then down to the North American Coast.
- Currently the only species a part of the Enhydra genus.
Origin
Subspecies
- The sea otter is the heaviest (the giant otter is longer, but significantly slimmer) member of the family Mustelidae
- The sea otter is so different from other mustelid species that, as recently as 1982, some scientists believed it was more closely related to the earless seals.
Subspecies
E. l. lutris
- Nominate subspcies (Enhydra lutris lutris)
- Trinomial Authority: Linnaeus, 1758
- AKA:
- Common sea otter
- Asian sea otter
- Commander sea otter
- Kuril sea otter
- The largest subspecies, with a wide skull and short nasal bones
E. l. lutris
- Located from the Kuril Islands to the Commander Islands in the western Pacific Ocean
E. l. nereis
- Trinomial Authority: Merriam, 1904
- AKA:
- Southern sea otter
- California sea otter
- Has a narrower skull with a long rostrum and small teeth
- Found on the coast of Central California
E. l. nereis
E. l. kenyoni
- Trinomial Authority: Wilson, 1991
- AKA:
- Northern Sea Otter
- Found inAlaska and the Pacific west coast from the Aleutian islands to British Columbia, Washington, and northern Oregon;
- After being extirpated from southern British Columbia due to overhunting, it has since been reintroduced off Vancouver Island and the Olympic Peninsula
E. l. kenyoni
Biology of Enhydra Lutris
- The sea otter is one of the smallest marine mammal species, but it is the heaviest mustelidae.
- Unlike most other marine mammals, the sea otter has no blubber and relies on its thick fur to keep warm.
- The sea otter has the ability to reach and groom the fur on any part of its body.
- Capable of speeds of up to 6mph.
Behavior
- The sea otter is diurnal.
- A sea otter must spend each day foraging range from 24 to 60%
- Sea otters spend much of their time grooming
Behavior
Social Structure
- Each adult and independent juvenile forages alone, sea otters tend to rest together in single-sex groups called rafts
- The species exhibits a variety of vocal behaviors.
- Not considered to be truly social animals
Social Structure
Reproduction and Life Cycle
- Sea otters are polygynous.
- Mating takes place in the water and can be rough.
- Births occur year-round.
- Capable of delayed implantation.
- Birth usually takes place in the water and typically produces a single pup.
- In the wild, sea otters live to a maximum age of 23 years.