John Gryphon
Well-Known Member
River otters at a Northern California lagoon have learned to climb onto resting brown pelicans, grab them by the neck, drag them underwater, and hold them there until they drown. The behavior was first documented in 2006. By 2024 the otters were taking multiple pelicans in a single hunt.
Abbotts Lagoon sits inside Point Reyes National Seashore, an hour north of San Francisco. It is a shallow coastal lagoon where brown pelicans raft on the surface between fishing runs, floating with their wings folded, dozing in loose groups. River otters live in the same water, hunting fish, crabs, and waterbirds year-round. At some point before 2006, the otters at Abbotts Lagoon and the nearby Rodeo Lagoon in the Golden Gate National Recreation Area figured out that a resting pelican on flat water is a target.
A river otter weighs roughly 20 pounds. A brown pelican weighs seven to eight pounds but carries a wingspan of over six feet. The otter is heavier. The pelican is dramatically larger in profile. On land or in flight, the pelican is untouchable. On the water, floating motionless, it is slow to react and cannot generate the wing speed needed to take off before the otter reaches it.
The attack is a drowning. The otter surfaces near a resting pelican, climbs onto its back or grabs the neck, and pulls the bird under. The pelican thrashes. The otter holds on. The bird cannot fly with a 20-pound mustelid attached to it and cannot fight underwater.
When the pelican stops moving, the otter tows the carcass to shore and feeds. Photographs submitted to the researchers show otters dragging pelican carcasses by the neck across the surface and feeding in groups on freshly killed birds.
Terence Carroll and Megan Isadore of the River Otter Ecology Project published the findings in the IUCN Otter Specialist Group Bulletin in 2025, calling brown pelicans a novel recorded prey choice for North American river otters. As far as anyone knows, this predator-prey relationship exists only in California. The earliest confirmed case was a single predation event at Lake Tolowa in 1998. The Rodeo Lagoon observation followed in 2006. At Abbotts Lagoon, regular predation has been documented since at least 2018, with photographic evidence from 2020, 2023, and 2024.
A June 2026 Audubon field report from Abbotts Lagoon noted that the behavior appears to be escalating. The observer wrote that this year, the otters were taking multiple pelicans during a single hunt more often than they ever had before. The otters are not trying this occasionally and giving up. They are refining the technique and increasing the frequency.
The study authors considered two explanations. The first is that otter predation on pelicans is an extension of an existing pattern. River otters at Abbotts Lagoon already eat waterbirds year-round, including ducks, coots, and grebes. Adding pelicans to the list is a step up in size but not a departure in method. The second is thermoregulatory economics. Otters lose body heat rapidly in cold Pacific water. Catching one large prey item that delivers a big caloric payoff in a single effort is more efficient than catching ten small fish. A pelican is a large, warm, calorie-dense package sitting motionless on the surface. From an energy standpoint, the math works.
A separate 2025 study published in Ecology and Evolution by Stuntz and colleagues found that river otter predation on seabirds is far more common across the Pacific and northern Atlantic coasts than the published literature had suggested. The phenomenon had been underreported for decades because it happens on remote coastlines where few researchers or birders are watching.
Both the otter and the pelican are recovering species in California. The brown pelican was delisted from the Endangered Species Act in 2009 after a dramatic DDT-era recovery. River otters, once nearly trapped out of Northern California, have been rebuilding their coastal populations for decades. Two species saved from decline, sharing the same lagoon, and one of them has discovered that the other is food.
Source: Carroll and Isadore (2025), IUCN Otter Specialist Group Bulletin / Stuntz et al. (2025), Ecology and Evolution / Audubon Magazine / River Otter Ecology Project.
Abbotts Lagoon sits inside Point Reyes National Seashore, an hour north of San Francisco. It is a shallow coastal lagoon where brown pelicans raft on the surface between fishing runs, floating with their wings folded, dozing in loose groups. River otters live in the same water, hunting fish, crabs, and waterbirds year-round. At some point before 2006, the otters at Abbotts Lagoon and the nearby Rodeo Lagoon in the Golden Gate National Recreation Area figured out that a resting pelican on flat water is a target.
A river otter weighs roughly 20 pounds. A brown pelican weighs seven to eight pounds but carries a wingspan of over six feet. The otter is heavier. The pelican is dramatically larger in profile. On land or in flight, the pelican is untouchable. On the water, floating motionless, it is slow to react and cannot generate the wing speed needed to take off before the otter reaches it.
The attack is a drowning. The otter surfaces near a resting pelican, climbs onto its back or grabs the neck, and pulls the bird under. The pelican thrashes. The otter holds on. The bird cannot fly with a 20-pound mustelid attached to it and cannot fight underwater.
When the pelican stops moving, the otter tows the carcass to shore and feeds. Photographs submitted to the researchers show otters dragging pelican carcasses by the neck across the surface and feeding in groups on freshly killed birds.
Terence Carroll and Megan Isadore of the River Otter Ecology Project published the findings in the IUCN Otter Specialist Group Bulletin in 2025, calling brown pelicans a novel recorded prey choice for North American river otters. As far as anyone knows, this predator-prey relationship exists only in California. The earliest confirmed case was a single predation event at Lake Tolowa in 1998. The Rodeo Lagoon observation followed in 2006. At Abbotts Lagoon, regular predation has been documented since at least 2018, with photographic evidence from 2020, 2023, and 2024.
A June 2026 Audubon field report from Abbotts Lagoon noted that the behavior appears to be escalating. The observer wrote that this year, the otters were taking multiple pelicans during a single hunt more often than they ever had before. The otters are not trying this occasionally and giving up. They are refining the technique and increasing the frequency.
The study authors considered two explanations. The first is that otter predation on pelicans is an extension of an existing pattern. River otters at Abbotts Lagoon already eat waterbirds year-round, including ducks, coots, and grebes. Adding pelicans to the list is a step up in size but not a departure in method. The second is thermoregulatory economics. Otters lose body heat rapidly in cold Pacific water. Catching one large prey item that delivers a big caloric payoff in a single effort is more efficient than catching ten small fish. A pelican is a large, warm, calorie-dense package sitting motionless on the surface. From an energy standpoint, the math works.
A separate 2025 study published in Ecology and Evolution by Stuntz and colleagues found that river otter predation on seabirds is far more common across the Pacific and northern Atlantic coasts than the published literature had suggested. The phenomenon had been underreported for decades because it happens on remote coastlines where few researchers or birders are watching.
Both the otter and the pelican are recovering species in California. The brown pelican was delisted from the Endangered Species Act in 2009 after a dramatic DDT-era recovery. River otters, once nearly trapped out of Northern California, have been rebuilding their coastal populations for decades. Two species saved from decline, sharing the same lagoon, and one of them has discovered that the other is food.
Source: Carroll and Isadore (2025), IUCN Otter Specialist Group Bulletin / Stuntz et al. (2025), Ecology and Evolution / Audubon Magazine / River Otter Ecology Project.
