In December, the Monterey Bay Aquarium near San Francisco, California, announced that one of their sea otters have adopted a little hero of the coast – a baby Southern sea otter. The baby, or pup, is named Pup 671, and is the newest player in a huge rescue mission happening along California’s coast. The mission is to save the iconic North Pacific sea otter, California’s coastlines, and protect the lives (human and nonhuman alike) that live near the coast. When she is ready, Pup 671 will join the rescue mission in a protected marsh that extends inland from Monterey Bay as the newest actor in the fight to save California’s land, ocean, and populations.
Sea otters (Enhydra lutris) weren’t always considered heroes or worthy of such elaborate rescue missions. From 1741 to 1911 sea otters were hunted for their protection against cold ocean water: waterproof, dense fur. In fact, sea otters have the densest fur in the animal kingdom – they have nearly 1 million hairs in each square inch. By 1911, about 99% of the sea otter population had been killed, and everyone believed that California’s population of sea otters (Enhydra lutris nereis) was extinct. At this point, countries around the northern Pacific Ocean realized that sea otters had an important role to play in their environment and banned hunting sea otters. The countries also began funding efforts to increase the population of sea otters around the ocean, beginning the rescue mission Pup 671 will join.
Spies researching the wild population, as well as studying the sea otters living in captivity, noticed that sea otters are heroes twice over. First, sea otters prefer to live near estuaries, where rivers pour into the ocean, and dense areas of kelp. They eat mainly invertebrates such as sea urchins, snails, and crabs that filter the water around them for minerals and nutrients. These invertebrates also filter pollution out of the water, but pollution remains in their bodies instead of digesting out (bioaccumulation). When a sea otter eats the polluted invertebrates, the sea otter also begins to gather pollution in its body (biomagnification). Since sea otters need to eat from 25-30% of their body weight per day to keep warm, so they will inevitably eat a lot of polluted invertebrates. Pollution gathering in a sea otter’s body will quickly make it sick or die. Because all sea otters quickly show the effects of pollution in their environments, those spies (scientists) recognize this heroic role by naming sea otters an indicator species.
When people hunted the sea otters they didn’t know that sea otters were important to their environments, but with the spies’ information we recognize sea otters’ heroism with another title. Sea otters are the top predators for estuaries’ food web (interconnected lines mapping the flow of energy from plant producers through animal consumers). The food web plus the non-living parts of a particular area (in this case, the estuary) is an ecosystem. We know that sea otters eat invertebrates, keeping their populations to a healthy level within the estuary. As there are many kinds of invertebrates within the estuary, sea otters provide opportunities for more rare species of invertebrates to survive by eating the more common invertebrates. Now add that these invertebrates eat the native marsh grasses like kelp and eelgrass. If there’s no native grass to use nutrients that flow into the marshes, algae toxic to the ecosystem’s health will grow. Many fish species harvested for human eating only grow up in native marsh grass. Since sea otters keep the population of invertebrates to a healthy level, native grass is able to outcompete algae. These plants filter out and deposit into the estuary’s marshes soil eroded farther inland, which in turn keeps the coastline stable for the estimated 75% of the nation that will live near coasts by 2025. Sea otters are the primary agents responsible for the ecosystem’s complexity, so they deserve the honorary title keystone species.
Back to our baby hero, Pup 671. When she’s grown in about eight months, she’ll be sent off to the Elkhorn Slough National Estuarine Research Reserve, a federally protected arm of the Monterey Bay Estuary. In order to track the success of the rescue mission Pup 671 joins, spies will follow her actions and those of the sea otter population she joins. These spies have several ways of tracking the success of the rescue mission, all of which is available to the public. We humans have roles to play in the sea otters’ rescue mission: choose food, shelter, and transportation options that reduce pollution and include our larger ecosystems in our building decisions. For sea otters, the rescue mission has helped save their species from extinction and provides support for their homes and food. Humans also benefit from food, water, air, and protection for our shelters. In fact, sea otters like Pup 671 have a large impact on California’s land, water, air, and coastline.
“Biology of the Southern Sea Otter « The Otter Project.” Accessed January 8, 2015. http://www.otterproject.org/about-sea-otters/biology-of-the-southern-sea-otter/.
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Delahoussaye, James. “More Than Just Cute, Sea Otters Are Superheroes Of The Marsh.” News. NPR.org, December 14, 2014. http://www.npr.org/2014/12/14/370670678/more-than-just-cute-sea-otters-are-superheroes-of-the-marsh.
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Maldini, Daniela, Caitlin Ward, Arianna Cecchetti, and Jessica Riggin. “Southern Sea Otter Diet in a Soft Sediment Community.” Journal of Marine Animals and Their Ecology 3, no. 1 (2010): 27–36.
SeaWorld. “Diet & Eating Habits.” Accessed January 18, 2015. http://seaworld.org/animal-info/animal-infobooks/otters/diet-and-eating-habits/.