Great horned owls sit near the top of the food chain, and very few animals actively hunt them. Adults have almost no natural predators. The real threats come during their vulnerable early life stages, from other great horned owls competing for territory, and from a range of human-caused dangers that kill far more of these birds than any predator does.
Nest Predators Target Eggs and Owlets
The most vulnerable period in a great horned owl’s life is before it can fly. Raccoons and crows are the most common nest raiders, stealing both eggs and young owlets. Since great horned owls typically nest in open platforms or abandoned hawk and crow nests rather than enclosed cavities, their young are relatively exposed. A parent owl is a fearsome defender, but it can’t guard the nest around the clock, especially when it leaves to hunt.
This early vulnerability shows clearly in survival data. Banding studies found that 46 percent of great horned owls died within their first year of life. After surviving that dangerous first year, annual mortality drops to around 31 percent, reflecting the massive advantage that size, flight ability, and experience provide.
Other Great Horned Owls
Great horned owls are fiercely territorial, and encounters between adults can turn fatal. Researchers in 1974 documented one adult great horned owl feeding on the body of another in winter conditions, with evidence suggesting the kill was fresh. While outright cannibalism isn’t an everyday event, territorial fights between adults are a recognized cause of injury and death, particularly during breeding season when pairs aggressively defend their nesting areas. Young owls dispersing into established territories face the highest risk of these encounters.
Golden Eagles and Other Large Raptors
Golden eagles are one of the few birds large enough and powerful enough to kill an adult great horned owl. These interactions are rare because the two species are mostly active at different times of day, but golden eagles will attack great horned owls found roosting during daylight. In areas where their ranges overlap, particularly in the western United States and Canada, golden eagles represent a genuine, if uncommon, predatory threat. Northern goshawks have also been documented killing great horned owls on occasion, though this is similarly rare.
Human-Caused Deaths Are the Biggest Threat
The largest category of great horned owl mortality comes not from natural predators but from human activity. A U.S. Geological Survey study examining 132 great horned owl deaths found that shooting and electrocution from power lines were among the leading causes, with 12 owls killed by gunfire and nine by electrocution. Vehicle strikes are another major killer, since great horned owls hunt along roadsides at night and fly low across highways while pursuing prey.
Rat poison poses a particularly insidious danger. When a great horned owl eats a mouse or rat that has consumed anticoagulant rodenticide, the poison accumulates in the owl’s body. A Texas study that screened 53 great horned owls found that nearly 51 percent tested positive for at least one rodenticide compound, with many showing exposure to multiple types. About a quarter of those poisoned birds had levels in the lethal range. The poison causes organ failure, internal bleeding, and increased vulnerability to injuries and infections. An owl doesn’t have to eat a single large dose to be affected. Repeated meals of poisoned rodents build up over time.
Disease and Parasites
West Nile virus has emerged as a significant threat to great horned owls. During a 2002 outbreak in Ontario studied by the CDC, great horned owls were among the owl species affected, with a documented death rate among exposed birds. Owls contract the virus through mosquito bites, and unlike some bird species that tolerate infection relatively well, owls of several species are highly susceptible. Trichomoniasis, a parasitic infection often contracted from eating infected pigeons and doves, can also cause fatal throat and crop lesions that prevent owls from eating.
Why So Few Predators Target Them
An adult great horned owl is a formidable animal. They weigh up to about 5.5 pounds, have a wingspan stretching over 4 feet, and their grip strength is estimated at around 300 pounds per square inch, comparable to a large dog’s bite. Their talons can pierce through thick leather. They hunt silently, see well in near-total darkness, and will aggressively attack animals many times their size when defending a nest. Most predators simply have easier, safer meals available. The great horned owl’s position as an apex nocturnal predator means that the threats it faces are less about being hunted and more about the cumulative dangers of poison, infrastructure, and the rare territorial clash with its own kind.