BIO 227:3: Wh-Otter We Doing to Save These Critters?

The Southern Sea Otter

Enhydra Lutris Nereis

By: Sarah Dowthwaite

Image by "Mike" Michael L. Baird, from Wikipedia Commons

Intelligent, playful, cute and cuddly. Aquatic, mammalian, fuzzy and furry. So furry, in fact, that more than a century ago the Southern Sea Otter nearly became extinct due to over-exploitation of their fur, known to be the thickest of all mammals. Since the early twentieth century, they've been protected by the International Fur Seal Treaty and made a remarkable recovery. But today they face new threats, beyond hunting, that are much, much worse than we realized.

At full size, males are about 65 lbs and 4 1/2 feet long, females about 45 lbs and 4 feet long. Females typically reach maturity at about 3 years, and males 5, but their first offspring likely won't survive. Approximately 75% of otters don't live past one year, contributing to a low population growth rate. When they want to eat, they have a large menu to choose from, including crabs, urchins, clams, abalones, mussels, and snails.

Image from thedailyotter.org

The Southern Sea Otter resides along the Central California coast, stretching from San Mateo County to Santa Barbara County. Before their decline, they covered the entire west coast of the North American continent. Between 1976 and 1984, the Southern Sea Otter population had dropped by 25%, consisting of only 1,300 individuals. While they initially recovered rapidly, nearly doubling the population within 10 years, they faced another decline by 1995 that lasted nearly 5 years, and thus were added to the Endangered Species Act in 1987 (revised in 2003) as a Threatened Species.

In addition to low population levels, a recovery plan was established for these critters due to a potential increase in environmental factors. These include oil spills, injury from fishing equipment, and pollution.

Graph represents sea otter carcasses removed each year.
Graph from U.S. Fish and Wildlife Service

The most recent decrease in the Southern Sea Otter is contributed to several factors. Otters only breed one pup a year and have trouble increasing their population size, which grows less than 5% each year. Additionally, as their population began to increase during the mid 1980s to 1990s, they had denser populations which eventually led to a smaller food supply. There's also speculation over trapping equipment that could be drowning otters, but no research has been done to prove this. The largest threat to sea otters, however, is disease, contributing to nearly 40% of deaths. According to the U.S. Fish and Wildlife Service Recovery Plan, "the growth rate of the California [sea otter] population would be substantially higher in the absence of disease."

To counteract these forces, the U.S. Fish and Wildlife Foundation created a recovery plan. First on the agenda is to determine what is contributing to the pollution and disease and to measure these levels over a period of time. Once researchers pinpoint the factors, organizations like the California Department of Fish and Game, the National Oceanic and Atmospheric Administration, and the National Marine Sanctuaries can work to minimize them and monitor stress and disease levels in otters through tissue samples. With the help of aquariums and sanctuaries, the foundation aims to increase public involvement and awareness about the Southern Sea Otter through educational programs and expanded opportunities.

Image from seaotters.org

And An-Otter Thing...

(a few cool facts about these guys)

Unlike most marine mammals, otters have almost no fat or blubber. To keep warm, they trap air bubbles within their dense fur, which can grow to be as thick as 650,000 follicles per square inch (that's about 4x the amount of our entire head!)

In addition to their fur, otters keep warm by consuming nearly 25-30% of their body weight in food every day. A male otter may eat 25 lbs of food in one day.

Otters have a high metabolism - nearly 25x greater than most land animals - to digest this large intake of food.

While sea otters spend nearly all their time in the water, they hardly dive deeper than 20ft under water. They float on their backs on the surface for most of the day.