Citizen scientists assist the HSU Wildlife Department in River Otter research

By August Linton

Since 1999, the River otter demography study headed by HSU professor and wildlife researcher Jeff Black and various others has collected reports of river otter (Lontra canadensis) sightings from citizen scientists in Humboldt and surrounding counties. In their online survey, the study asks people who have seen river otters for a variety of information. This includes the location of the sighting, the type of habitat, the number of animals in the group (or “bevy”,) behavior, prey items, and whether there were any pups present. Most of the papers based on this data have zeroed in on demographics, but Black says that his recently-published paper focuses more on behavioral observations.

The study is citizen science-based. It depends on information submitted by people who stumble upon otters in their natural habitat: along rivers or in coastal marine environments like estuaries and marshes. Researchers advertise by posting signs
near otter habitats as well as promoting the study online. Black says that most submitted sightings from non-researchers or students come from those involved in outdoor recreation, like kayakers, surfers, and hikers. Given that not all sightings come from individuals with a strong scientific or wildlife background, the study has established criteria for what information it considers scientifically valid. A paper published by Black based on the study in 2009, “River Otter Monitoring by Citizen Science Volunteers in Northern California: Social Groups and Litter Size,” states that “records of pups were included only when observers commented on their size,” for example. This rule eliminated 27% of litter observations in an effort to ensure the accuracy of reports.

“Some records would come in where for example they’d be describing a seal instead of an otter,” Black said.

He described a record he once received which counted over one-hundred otters—which normally exist in much smaller groups—sighted at the location of a well-known seal hangout above Arcata.

According to Black and the study’s website, the population of river otters can indicate the health of an entire ecosystem, making the information which is gathered extremely important.

“It’s argued that when otters disappear from the habitat, there’s probably heavy pollution involved, which kills the fish, and then there’s nothing to eat for the otters,” said Black.

The study has been monitoring northern California otter populations for over 20 years. Another paper which utilizes the study’s data, “Fifteen Years of River Otter Monitoring by Citizen-Science Volunteers in Northern California: Litter Size,” by Jeffrey M Black, Erin Wampole, and Jeanne E Mayer, states that “an average of 234 records was received per year, amounting to 3540 observations.”

“All our limited evidence from our citizen science group indicates [populations are] stable,” said Black.

The study is a very useful tool for researchers, especially as information on river otters in Northern California has historically been scarce, according to the study’s website. However, it’s only one of the methods utilized to study these creatures, and does not accurately catalogue every individual in the study area.

“We thought from the citizen science records that maybe we had 24 otters living in Humboldt Bay. Through collecting scat and then extracting DNA from the individual otter that put that scat down, we found that there were 48 individual otters,” said Black.

The study allows researchers to track trends in otter populations based on how many are seen each year, regardless of whether reports yield an accurate count. Those interested in submitting reports to the study can find the survey linked on the study’s website,, or email

The study plans to keep collecting data for the foreseeable future.

“I’ll be involved in it until I die,” said Black.

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