Scientific Name: Enhydra lutris
Found at Elkhorn Slough
Open salt water, beaches from the bay to the Reserve and salt marsh.
Did you know…
Sea otters eat 25% of their weight in food each day.
Sea otters are without a doubt the most popular animal here at the slough. Also known as the southern sea otter, this subspecies of otter is found from California to Washington with other subspecies found in Alaska, Canada, Russia, and Japan.
Here at the slough they can be found in open water or hauled out on the mudflats in the main slough channel, from Moss Landing harbor to Hudson Landing, but are most common in the North harbor area.
Otters eat clams, crabs, oysters, abalone, sea urchin and other small marine species including the fat innkeeper worm. Sea otters eat approximately 25% of their weight in food each day.
Adult female otters give birth to a single pup nearly every year. Pups are born with long hair – ready to keep them warm and buoyant right from birth. They are so buoyant in fact that they cannot dive underwater. From the moment otters are born they bond with and are meticulously cared for by their mothers. For the first few months of the pup’s life it s home will be on its mother’s belly, where it will be nursed, constantly groomed, protected from predators, and completely dependent upon its mother for survival. When the mother needs to forage for food, she will briefly leave her pup anchored in kelp or sea grass until she returns. When left alone, pups will call for their mothers.
It’s common to see sea otter mother and pups in the Elkhorn Slough. Our protected waters make for a perfect refuge. For the first time ever, a sea otter pup birth was witnessed in the wild by researchers in May of 2011. Read our press release, including pictures and videos about this exciting event.
Sea otters have between 500,000 and 1 million hairs per square inch of fur. Unlike other marine mammals who have a layer of blubber to keep warm, sea otters utilize their dense fur instead to help protect them from the cold water. Otters are also one of the few mammals that use tools. Otters commonly use rocks to crack open prey, such as gaper clams or crabs. It’s common to see otters with other items as well including bottles, bricks or even a video camera?!
A Little History
Sea otters once ranged from northern Japan to the Alaskan peninsula and along the west coast of North America to Baja California in Mexico. Until the 1700s, sea otters were abundant throughout the waters of the north Pacific and for centuries native groups, such as the Aleuts, hunted them. During this time, the worldwide sea otter population numbered between 150,000 and 300,000. By the mid-1700s, Russian hunters had coerced the Aleuts to exploit sea otters for the fur trade, and the once abundant sea otter population plummeted. English, French, Japanese and American traders chased down the otters that remained. By the 1900s, the sea otter was nearly extinct with only 1,000 to 2,000 otters left. Only 13 remnant sea otter colonies existed from Russia to Mexico when the International Fur Seal Treaty, which banned the hunting of sea otters and fur seals, was established in 1911.
By the 1930s, a small group of 50 to 300 sea otters–a population now known as southern or California sea otters–remained near Big Sur, California. Under the protection of the International Fur Seal Treaty, this small population began a slow and steady climb from near extinction to a fairly stable population. From the mid 1970s to the mid 1980s, the southern sea otter population began to decline once again. About 1,000 sea otters died over a 10-year period due to entrapment in gill nets. When legislation was passed in the late 1980s requiring gill net fisheries to move farther off shore, the sea otter population began to grow again until the mid-1990s. In 1977, the southern sea otter was listed as “threatened” under the Endangered Species Act.
The Elkhorn Slough will likely play an important role in the recovery of the California sea otter population. According to a 2010 Technical Report by Elkhorn Slough researchers, the slough and the adjacent Moss Landing Harbor area host roughly 5% of the statewide population of sea otters. There are many reasons otters are attracted to the quiet slough waters, and in contrast, there are also many factors here at the slough that could threaten their survival–like water quality and human recreation. Research and conservation will help us better protect these animals from further decline.
Locally, the Monterey Bay Aquarium’s Sea Otter Research and Conservation program has been studying and trying to save the threatened southern sea otter since 1984. They rescue, treat and release injured otters; raise and release stranded pups through their surrogate program; provide care for sea otters that can’t return to the wild; and conduct scientific research. Working with collaborators such as California Department of Fish and Wildlife, UC Santa Cruz, Elkhorn Slough National Estuarine Research Reserve and others, they are seeking to achieve the following five key conservation outcomes:
- Answer the Question: Why Do Sea Otters Die?
- Answer the Question: How Do Healthy Sea Otters Become Sick?
- Answer the Question: What Risk Factors Do Sea Otters Face in the Wild?
- Mitigate the Effects on Sea Otters of Potential Environmental Catastrophes
- Improve and Advance the Quality of Veterinary Care Provided to Sea Otters in Both Captive and Field Research Settings.
- Elkhorn Slough Reserve’s Otter Research and Monitoring
- Hughes, B.B., R. Eby, E. Van Dyke, M.T. Tinker, C.I. Marks, K.S. Johnson, K. Wasson. 2013. Recovery of a top predator mediates negative eutrophic effects on seagrass. In press. Proceedings of the National Academy of Sciences USA. Click here for more information and press coverage of this important research.
- 2013 USGS Sea Otter Research in Elkhorn Slough: www.werc.usgs.gov/elkhornotters
Fact sheet about the project: Elkhorn Slough Sea Otter Research Project (1.8MB, pdf)
- News: May 6, 2011 The Stork Visits Elkhorn Slough – otter pup birth witnessed in the wild!
- TECHNICAL REPORT 2010: Sea otters: factors that control distribution and abundance in Pacific Coast estuaries and a case study of Elkhorn Slough, California.
- 2010 Research Symposium presentation: Ecology of a sea otter raft. Daniela Maldini, Ron Eby, Robert Scoles and Mark P. Cotter, Okeanis. Download the presentation slides (2.57MB, pdf)
Videos: Find many more otter videos on our Youtube channel!