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2003 has brought an unusual parade of predators to the Bolinas Lagoon area: the first Black Bear in a century roamed our ridges, the first Bottle Nose Dolphins in memory showed off in Stinson, a Great White Shark supped on seals in the channel… and shy but playful River Otters spent a relaxing winter vacation in the Inner Lagoon.
Otters
once crowded California waterways, but were doomed to near-extinction by their
soft, waterproof fur, popular in China and Europe for hats and coats. Otters
can still be found in remote and unpolluted waters, but sightings are relatively
rare - often a reward for hikers or paddlers venturing up willowed, mosquito-laden
creeks.
By the early 1900’s, few otters were found in Point Reyes or anywhere else on the coast. Luckily, a remnant population continued in the Russian River, and it is this population that is slowly expanding southward. In 1985, a few otters were spotted in northern Tomales Bay; a mother with pups was seen in the southern bay a few years later. Before the Bolinas sightings, otters have been seen as far south as creeks near Five Brooks trailhead in the Point Reyes National Seashore.
The Bolinas Lagoon sightings are encouraging otters, picky environmentalists, apparently consider the Lagoon to be healthy, natural, and unpolluted. The health of a predator population is a direct indication of their environment it takes a healthy environment to support the large number of prey required to feed top predators.
Rivers Otters are members of the weasel family. Smaller than their cousins, the Sea Otters, River Otters have a longer tail and more pointy snout. Like the Sea Otter, they have many unique adaptations for aquatic life - tiny ear and nostril flaps that close when it goes under the water, and long whiskers to feel for food under water. They are mostly nocturnal and can best be seen in the early evening and early morning.
Like all weasels, River Otters are carnivores with sharp, strong teeth for munching small mammals, birds, amphibians, and fish. Especially fish. The otters in the Inner Lagoon likely fed on the abundance of Green Crab that have settled there.
An invasive, non-native, species, the Green Crab was accidentally introduced from the Eastern Atlantic to San Francisco Bay in the 1980’s. These small crabs are voracious predators, preying on any animal or plant they find along the shores and in the mud bottom. Nearly half a million are currently resident in the Inner Lagoon more than enough to satisfy a hungry otter’s appetite.
River Otter adults are usually solitary so why were four otters together in Bolinas Lagoon? Likely, the otters are young males seeking new territories. The average male home range may be up to 100 square miles, so the young need to venture far to find undefended habitat.
Perhaps the otters will make another appearance this fall; there are still plenty of crabs, and plenty of interest in helping them to re-establish their former range.
Three otters near the Highway 1 Harbor Seal Pullout last fall caused passersby to do a double-take at their distinctly non-Harbor Seal appearance. They remained near the Pullout, clamming and rolling in the mud, for several days.