The latest photos by Betsy Seeton

River Otter

2/20/2019

This river otter was photographed on an October afternoon in the San Juan archipelago.

I thought since I was seeing an otter in the sea, it would be a sea otter. I also thought a river otter would be an otter found only in non-salt water. I was wrong. What I now have photographed twice this past week is a river otter. Sea otters float on their backs and have shorter tails. Both are relatives of the weasel.

River otters digest and metabolize food so quickly that food passes through their intestines within an hour. They spend two-thirds of their time on land often making at least one permanent den on land, near the water, in addition to several temporary shelters. They are adept at being on land unlike the clumsy and rather awkward moving sea otter, who seldom spends 95% of their time in the water. Instead of blubber for insulation, otters have 250,000 to a million hairs per square inch.

Sea otters are active during the day and while river otters are technically nocturnal, they are active both in the day and at night. Around humans they tend to be much more nocturnal. River otters are often solitary creatures. When they are seen together, it would likely be a family unit such as a mother with her young.

Sea otters are a keystone species and, as predators, are critical to maintaining the balance of the near-shore kelp ecosystems. "Without sea otters, the undersea animals they prey on would devour the kelp forests off the coast that provide cover and food for many other marine animals." ~ Defenders of Wildlife

Sea otters have high metabolisms and need to eat 25% of their body weight daily. They consume over 45 marine species including urchins, abalone, mussels, clams, crabs, and snails.

There was a time when there several hundred thousand to a million sea otters until the fur trade slashed the number to fewer than 2,000 by the early 1900's.

The 1980's were hard on populations due to oil spills. The 1989 Exxon Valdez oil spill in particular, in Alaska’s Prince William Sound, killed several thousand sea otters. The oil ruins their fur's ability to keep warm enough in the frigid waters, as well as being toxic. Many died from hypothermia. Estimates put the current worldwide population at only around 106,000.

It took the Endangered Species Act — under which sea otters gained protection in 1977 — for a recovery to begin in earnest. "The saving of the sea otter," writes Glenn Vanblaricom of the University of Washington in his book on the animal, "is indeed one of the great success stories in marine conservation."

In addition to oil spills, there are other threats to sea otters.

Some shell fishers view sea otters as competition and a threat to their economic gain because otters like the same kind of food humans do and both fish in the same waters. Many fishermen use fishing gear that can entangle sea otters and cause them to drown. I met a man recently who talked about having to clean his boat because the otters like to sit on when it's stored. He said he'll shoot one the next time one makes too much of a nuisance.

Sea otters are often contaminated with toxic pollutants and disease-causing parasites as a result of runoff in coastal waters. "Scientists have also reported the accumulation of man-made chemicals, such as PCBs and PBDEs, at some of the highest levels ever seen in marine mammals." ~ Defenders of Wildlife

River otters will birth up to six babies in one litter. The average is half that. Sea otters have one baby and go longer between births. They give birth in the water, while river otters have their babies on land. Sea otter babies are more developed at birth with eyes open and teeth already emerging. River otters are much more helpless. They are blind when born and have no signs of teeth.