River otters have been observed hunting and killing brown pelicans at Abbotts Lagoon in Point Reyes National Seashore, California. Researchers documented this unusual predatory behavior, which includes drowning the large birds and then consuming them. This phenomenon was brought to public attention by wildlife photographer Daniel Dietrich, who captured footage in 2023 showing otters attacking two pelicans.
Wildlife researcher Megan Isadore, co-founder of the River Otter Ecology Project, reported witnessing a similar event in 2018. She described seeing an otter grab a pelican, drown it, and then begin to eat it. Isadore and her colleague Terence Carroll later investigated the lagoon, finding an increasing number of pelican carcasses. During a monitoring period from June to November 2023, they counted 73 dead pelicans. Most of the victims appeared to be younger birds.
The findings were published in the IUCN/SSC Otter Specialist Group Bulletin in April 2025. While the number of deaths was higher than previously observed, researchers stated it was not significant enough to threaten the overall brown pelican population. The attacks are considered rare, with prior documented instances occurring at Rodeo Lagoon in Northern California in 2006 and Lake Tolowa in 1998. No similar behavior has been documented outside of California.
Researchers have speculated on the reasons for this behavior. In the case of Rodeo Lagoon in 2006, it was suggested that depleted fish stocks due to excessive algae growth may have driven otters to prey on pelicans. However, Abbotts Lagoon has not exhibited these conditions, leading to speculation that the otters may have simply discovered the large birds are a substantial food source. "Pelicans are big and have a lot of meat on them," Isadore told SFGATE. "It's a lot of bang for their buck."
River otters are known to be opportunistic predators with high energy requirements, typically hunting fish, ducks, gulls, and cormorants. Despite their often-perceived docile appearance, they are described as fierce and hungry animals that will exploit easily accessible prey.
Following these repeated attacks, the behavior of the pelicans at Abbotts Lagoon appears to have changed. Isadore has observed pelicans actively flying away when otters approach, a behavior previously undocumented between the two species. Dietrich also noted a decrease in the number of pelicans venturing into the lagoon, even though they remain common in other areas of Point Reyes. This avoidance behavior may have contributed to a tapering off of the killings. Researchers are still investigating how this hunting tactic spread among otters and why the frequency of attacks has decreased.