Supporting Conservation - One Otter Sighting at a Time

Imagine standing on the bank of a creek in the rain, watching four otters hunt enthusiastically up and down the reach, nosing into every crevice. They raise their heads to crunch crawdads one after another, make chirping contact calls as they go, then roll around the shore scent-marking. They keep an eye on us, but don’t leave. We are quiet, thrilled to see these elusive animals.

Shortly after that day, we discovered that otters were officially considered non-occurring not only in that creek, but in most of the San Francisco Bay Area. We set out to find, document, and update the river otter range map using community science. We understood that river otters, highly attractive animals of great interest to many, could help to focus attention on improving habitat.

Otter Spotter crowdsources otter sightings. An Otter Spotter is someone who sees an otter and inputs the sighting to our handy  online form . The sighting is mapped and saved. Take a stroll through these pages, learn what it’s like to be an Otter Spotter, how our results changed the range map, who uses that information, and what we are planning for the future.

We believe in involving everyone with an interest in community science as partners on our project—supporting watershed health through research, and education.

River otters are fascinating animals, medium sized predators thriving in the densely-populated San Francisco Bay Area. Their presence excites people, gets them chatting, galvanizes some of them to help preserve and protect habitat and watersheds. That’s conservation in action.

The stories Otter Spotters tell are sometimes charming, sometimes emotional, sometimes questioning, and always interesting. We’ve gathered some examples here – enjoy! And if you see an otter, you know what to do –  submit your sighting  and become a community scientist, part of our trusty cadre of nature lovers and protectors.

You can spot otters all over the Bay Area and throughout much of Northern California.

Look around any waterway! River otters are happy in fresh, brackish and salt water. They’re often seen in coastal areas near the mouths of rivers and creeks, marshes and wetlands. They’re a little harder to see along vegetated rivers but keep looking, especially when you’re boating. They’re often found in lakes…look where the fish congregate. If lakes are stocked, otters will follow that activity closely. Check out the map above to see where they're often reported.

Otters are normally dangerous only to their prey items, like fish, insects, crustaceans, and birds. If you see otters, remember that even though they are cute and playful, they are wild animals. Don’t approach them, just enjoy watching from afar. Do not let dogs chase or bother them, and do not feed them.

If you’re swimming and encounter otters, back off and keep away. Normally they are shy of humans, but if they have young with them, they can become aggressive. It is not normal for otters to attack humans, but it does happen very occasionally.

River otters are most often seen at dusk and dawn, but can be seen at any hour of the day or night.

Look for large ripples on the surface of the water, lots of bubbles and a 3- to 4- foot-long animal with a long thick tail. The tail is about a third of the body length of the otter. Otters are dark and sleek in the water, with small heads and ears. Often you will just see the ripples and a very small head. Otters have a large black hairless nose (rhinarium). Some animals often mistaken for river otters:

• Muskrats, much smaller than otters, upper left photo
• Nutria, rodents with orange teeth, upper right photo. If you see a nutria in California, please photograph it and report it via email to:  invasives@wildlife.ca.gov 
• Harbor seals, much bigger than otters, with a different color and shape, middle left photo
• Beaver, large rodents with orange teeth and a large flat tail, middle right photo
• American Mink, bottom left photo
• Sea otter, bottom right photo

Note how all the rodents have similar fur.

For more information on identifying river otters, please see our  Field Guide, Field Etiquette, and How to Identify a River Otter. 

Fill in the form below and your sighting will appear on the map above within a few days. Thank you for your sharp eyes. Don’t forget a photo if you can get one. Even bad or blurry photos are fine; we just want to be able to see that it’s an otter.

Welcome Back Otters!

Historically, river otters were present all over the Bay Area, but as wetlands along San Francisco Bay (the largest estuary in North America) were filled to provide more land for people and industry, the waters became polluted, fish stocks and habitat grew less attractive to wildlife, and otter presence dwindled. Nobody paid much attention to river otters for decades. Trapping for river otter pelts, while never apparently a large business around the SF Bay, was banned in 1961.

The original California Department of Fish and Wildlife (CDFW) range map for river otters was based on a map in California Wildlife, Vol. I-III, edited by Zeiner et al., and published from 1988-1990. In 2017, we provided a dataset of approximately 1,500 northern California Otter Spotter sighting records to CDFW, and requested that the agency consider updating the range map. They agreed, and off-and-on over the next two years we worked with CDFW’s Biogeographic Data staff to determine the areas that should be included in the updated map. 

The updated range map represents the best available information on river otter presence over the past 20 years. Historic presence is also included unless there is substantial evidence that river otters were extirpated from an area. For the updated map, presence was determined from the original map, our Otter Spotter data, local agency data, published reports, and expert opinion. Presence was mapped using the USGS HUC12 Watershed Dataset Boundary delineation. Identified presence in any part of a Watershed Unit was mapped as presence in the entire Watershed Unit.

“Otter Spotter sightings added about 4,100 square miles of Bay Area habitat to the 2019 river otter range map. The maps can help planners know which lands to conserve for habitat and connectivity,” Melanie Gogol-Prokurat, Ecologist, California Department of Fish & Wildlife.

“I've been watching the river otters here for years and just discovered your project. They are here consistently. There are homes on the creek and the otters climb on the docks to eat … I think they are incredible and I never get tired of watching them.” Otter Spotter Henry Bornstein. 

The otters’ expansion here reflects the headway we’ve made in cleaning up waterways and restoring wetlands. River otters are big eaters, and the fish, crayfish, and other prey they depend on need unpolluted water to thrive. “If there’s enough food for river otters, there’s a healthy environment too,” Sarah Allen, Ph.D. Science Program Lead, National Park Service Western Region (retired).

A consideration of who uses the river otter range map data stresses the importance of protecting entire watersheds for our shared benefit. Each of the users illustrated here work in tandem with the others to ensure healthy watersheds. None can be effective on their own. We support the “Fifty by fifty” endeavor to protect 50% of San Francisco Bay Area lands by 2050, as it is only through supporting a web of connected protected lands and waters that we can heal and support ecological function on our planet.

When river otters die from disease or old age, they are not often found. When they are killed in road accidents, they may be noticed and reported to River Otter Ecology Project. We take the opportunity whenever possible to salvage the bodies and discover what we can about their health status.

In partnership with the California Department of Fish and Wildlife and the California Academy of Sciences, we have formed a salvage team to collect river otter carcasses for necropsy (animal autopsy) and to support the Academy’s specimen collection.

The CDFW Wildlife Health Lab has performed necropsies on 23 river otters during 2013 through 2021, finding evidence of trauma, pneumonia, hepatitis, meningitis, gunshot wound, infections, natural poisoning (not human-caused), and some evidence of rodenticides, though not in high enough concentration to cause death 

The California Academy of Sciences Ornithology and Mammalogy Department collects specimens to help in compiling a wealth of data on the evolution of these organisms, their distribution around the world, and how they are responding to changes in the environment.

The more we understand about the way otters respond to their world, the diseases and changes they exhibit, the better our ability to support conservation of otters and watersheds.

A tantalizing question we have not yet answered is how far into San Francisco’s South Bay are river otters living and reproducing? We know river otters are common in coastal California north of San Francisco. Despite many surveys on foot as well as widespread outreach, we have not discovered any otter presence along the coast from San Francisco southward. There is habitat available, but as yet, no otters.

Are river otters slowly expanding southward through the East Bay? Will they get to the coast, and when? These are questions to which we hope Otter Spotters will help find the answers.

On the above map, the blue points in the South Bay represent unconfirmed otter sightings.

When our project began in 2012, we sought to discover where in the San Francisco Bay Area river otters thrived. Since then, we have expanded our horizons to include all of California, and now all of North America.

We welcome otter sightings from all states and provinces. We are careful about mapping the sightings, as we are protective of otters and have no wish to “out” sensitive sites. If we or the community science Otter Spotter judges any site to be worth keeping secret, we do not show it on the map, but only add the information to our database.

At River Otter Ecology Project we often look at our programming and planning through this lens: why and how are we making a difference to conservation, to equity, inclusiveness, and diversity? Which of the many ideas we have will be of most use? Which do we have the resources to try?

One idea we are exploring currently is using the excitement over urban otters to contribute to underserved urban communities. We are looking at how we can serve specific communities’ needs using our education, outreach, and community science work.

As we gather information, input, and resources to carry this effort forward, we will continue to use our base of community science support through Otter Spotter both to discover where otters and communities intersect, and where our project is able to support the goals of underserved communities.

Click  here  to learn more about our published research.

With greatest appreciation to the Otter Spotters who input their sightings and make community science valuable.

Many thanks to Kelsey Wright of the College of William & Mary - our invaluable ArcGIS Story Map creator.

We owe an enormous debt of gratitude to the  Institute for Integrative Conservation  at the College of William & Mary for their support of our Story Map.

With sincere thanks to all the photographers who generously allowed us to use their photos. To view the credit for any photos or videos, scroll over the top left corner and click on the "i" symbol. The cover photo is by Bob Gunderson.

Thank you to California Department of Fish & Wildlife, Rose Foundation for Communities & the Environment Environmental Grassroots Fund, Landsberg Foundation, and CuriOdyssey.

And to the IUCN/SSC Otter Specialist Group for great encouragement from the beginning.