Amusing Monday: Sea otters often play a key role in kelp forests

Last week was National Sea Otter Awareness Week, recognized by many aquariums, marine educators and environmental groups across the country. Although I was on vacation last week, I thought I could still bring up some interesting facts about these amusing and ecologically important creatures.

I guess I should mention first that sea otters are rarely spotted in Puget Sound. If you do see an otter — whether in saltwater or freshwater — it is most likely a river otter. I’ll outline some differences between the two further on in this blog post.

Occasionally, sea otters have been sighted in Puget Sound as far south as Olympia, but their historical range is described as the outer coast from Alaska to California — including the Strait of Juan de Fuca west of Port Angeles, according to a new report (PDF 1.4 mb) by the Washington Department of Fish and Wildlife.

Heavily hunted for their dense fur starting in the late 1700s, sea otters were extinct in Washington state by 1910. In 1969 and 1970, 59 sea otters were taken from Amchitka Island, Alaska, and placed at Point Grenville and La Push on the Washington Coast. Since 1989, the sea otter population has grown faster than 9 percent per year on average, reaching somewhere around 1,750 animals in the state today, according to the WDFW report.

In August, the species was reclassified by the Washington Fish and Wildlife Commission from a status of “endangered” to the lesser “threatened” under Washington state law. Check out the commission’s news release.

As their coastal population has grown, more sea otters are being spotted within the Salish Sea, which includes Puget Sound, the Strait of Juan de Fuca and the Strait of Georgia in British Columbia.

One sea otter, named Ollie, has gained a notable following among boaters, who often see him swimming in the Race Rocks Ecological Reserve at the southern tip of Vancouver Island — directly across the Strait of Juan de Fuca from Port Angeles. Ollie even has his own Facebook page.

Sea otters, the smallest of the marine mammals, are considered a “keystone species,” because they have the potential to thoroughly alter their ecosystem. Because they eat sea urchins and other marine creatures that consume kelp, sea otters encourage the growth of kelp forests, which in turn support a diverse community of other species.

Sea otters must consume enough food to total 20-30 percent of their body weight each day to maintain their high metabolic rate. Unlike other marine mammals, they don’t rely on a layer of blubber to protect them from the cold. Instead, they maintain a coat of thick fur for insulation, which involves lying on their backs and grooming themselves when not resting or eating.

The fur of sea otters is about 1,000 times denser than a person’s head of hair, and each shaft of sea otter fur has many more scales than a human hair. A sea otter grooms itself by squeezing water from its fur while blowing air to fluff up its coat. An otter may roll onto its side to wash away scraps of food while eating on its back.

While resting, sea otters fold their front paws together and hold their back paws above water to avoid heat loss through their furless footpads. To stay in groups, called rafts, sea otters may hold hands while sleeping, or they may wrap kelp around their bodies to avoid drifting away in tidal currents.

The videos on this page include 1) an amusing conversation with a sea otter, 2) facts about sea otters, 3) a montage from Vancouver Aquarium, and 4) a live shot at Seattle Aquarium. The two “otter cams” at Seattle Aquarium are operated each day from 9 a.m. to 6 p.m.

Some of the differences between sea otters and river otters:

  • Sea otters are two- to four-times larger than river otters.
  • Sea otter tails are short and flattened, while river otter tails are long and pointy.
  • Sea otters have rear flippers that are much larger than their front feet, while river otters have webbed limbs that are roughly the same size.
  • Sea otters rarely venture onto land, where their movements are clumsy. River otters frequently slink along the shore, where they can sprint at high speed.
  • Sea otters swim mostly on their backs to conserve heat but can dive deeper and stay under water longer than river otters, which paddle through the water mostly submerged using all four webbed feet.
  • Sea otters are generally active during the day, while many river otters forage at night.
  • Sea otters often congregate in large groups, although maies and females stay separate most of the time. River otters are loners, though they may be seen in small family groups.
  • River otters reach sexual maturity at a younger age than sea otters. River otters tend to have one litter per year with up to four pups. Sea otters have only one pup at a time with longer intervals between births.
  • Sea otter pups are born in the water with open eyes and emerging teeth. River otter pups are born in dens on land with their eyes closed and are completely dependent on their mothers.

Sources: Pets on mom.me, Outdoor Revival, Seattle Aquarium, and U.S. Fish and Wildlife Service.

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