Squirrels face threats from an remarkably wide range of predators, spanning hawks and owls in the sky, foxes and coyotes on the ground, rattlesnakes below, and even domestic cats in suburban yards. The list is long enough that squirrels have evolved some of the most sophisticated anti-predator defenses in the animal kingdom, including infrared signaling and predator-specific alarm calls. Yet despite all this pressure, predation alone rarely controls squirrel populations. Food supply, especially tree seed availability, tends to matter more.
Hawks, Owls, and Eagles
Birds of prey are among the most consistent squirrel predators across the globe. In conifer forests of northern England, northern goshawks take red squirrels regularly during the breeding season, with researchers estimating roughly 79 squirrels removed per breeding season in one large forest, though the annual take varied wildly from as few as 8 to as many as 261 depending on how good the seed crop was that year.1Biological Conservation. Predation of red squirrels by northern goshawks in a conifer forest in northern England: can this limit squirrel numbers and create a conservation dilemma? Even so, squirrels made up a small fraction of the goshawks’ overall diet, which was dominated by pigeons, crows, and game birds.
Owls are just as important, particularly for smaller and nocturnal squirrel species. In Finland, long-term diet studies of Ural owls and eagle owls showed that both regularly consumed Siberian flying squirrels and red squirrels over a 55-year period. Interestingly, flying squirrel consumption by owls tracked vole abundance: in years when voles were plentiful, owls also ate more flying squirrels, likely because both prey species were more active or abundant in the same conditions.2Animal Conservation. Decline of flying and red squirrels in boreal forests revealed by long‐term diet analyses of avian predators Ural owl presence had a strong enough effect that flying squirrels avoided nest boxes in areas where owl predation risk was high.3PLOS ONE. Predation risk landscape modifies flying and red squirrel nest site occupancy independently of habitat amount
In the Pacific Northwest, northern spotted owls depend heavily on northern flying squirrels. In Washington and Oregon, flying squirrels were the spotted owl’s most common prey, and in areas where owl predation was intense, flying squirrel populations were noticeably depressed.4Ecological Monographs. Northern Spotted Owls: Influence of Prey Base and Landscape Character This is one of the relatively rare cases where a predator appears to actually suppress squirrel numbers locally. Golden eagles also take ground squirrels, and their reliance on them can shift with habitat changes. After wildfires destroyed shrub cover in one study area, golden eagles were about 1.6 times more likely to hunt Piute ground squirrels than before the fire.5Ornithological Applications. Golden Eagle dietary shifts following wildfire and shrub loss have negative consequences for nestling survivorship
Coyotes, Foxes, and Bobcats
On the ground, squirrels face a different set of hunters. Coyotes are prolific ground-squirrel predators across much of North America. On ranches in western Canada, Richardson’s ground squirrels were the most common prey for coyotes, which hunted them while moving among cattle herds.6Canadian Journal of Zoology. Pest or pest control? Coyote interactions with cattle and Richardson’s ground squirrels This relationship creates an odd dynamic for ranchers: coyotes sometimes worry cattle, but they also provide free pest control by suppressing ground-squirrel populations that damage pastures.
Foxes prey on squirrels in both the Americas and Europe. In Mexico, gray foxes are among the most important predators of Peter’s squirrel, while in Spain, red foxes fill the same role for Eurasian red squirrels. Researchers studying these systems found that squirrels have adjusted their activity patterns to minimize overlap with these predators, keeping ground activity confined to times when foxes and other carnivores are less active.7Journal of Zoology. Predation risk in tree squirrels: implications of the presence of free‐ranging dogs Ringtails and opossums also appeared as squirrel predators in the Mexican system, though with even lower temporal overlap, suggesting squirrels are quite good at avoiding them.
Bobcats round out the medium-sized mammalian predators. In the northern parts of their range, bobcats eat a lot of squirrels. A study of winter bobcat diets found that red squirrels and other rodents made up more than 78% of the dietary biomass, outpacing larger prey like snowshoe hares and deer.8PubMed Central. Regional differences in winter diets of bobcats in their northern range In deep snow, squirrels are at a disadvantage against bobcats, which can navigate soft ground more effectively with their large, well-furred paws.
Pine Martens and the Tree Canopy
Most mammalian predators hunt squirrels from the ground, but pine martens are an exception. These agile, cat-sized carnivores are skilled climbers and pursue squirrels through the canopy itself. In Ireland and Britain, both red and grey squirrels turned up in pine marten scat, confirming them as genuine predators rather than occasional scavengers. Grey squirrels were taken significantly more often than red squirrels, and only during spring and summer.9Mammalian Biology. The dynamics of pine marten predation on red and grey squirrels
This selective predation has had major conservation implications, which are covered in more detail later in the article. The key point here is that martens occupy a unique niche as arboreal predators capable of following squirrels into their own habitat, unlike foxes or coyotes, which can only grab squirrels that come to the ground.
Rattlesnakes and the Ground Squirrel Arms Race
The relationship between rattlesnakes and ground squirrels is one of the best-studied predator-prey interactions in biology, and it goes far beyond simple predation. Rattlesnakes are ambush predators that sit in wait near squirrel burrows, and over millions of years, ground squirrels have evolved physiological resistance to rattlesnake venom. This resistance varies geographically: squirrel blood serum is more effective at neutralizing venom in some areas than others, and rattlesnake venom potency varies in parallel. Research has shown that rattlesnakes are the locally adapted side in this arms race, meaning their venom tends to be slightly ahead of the local squirrels’ resistance.10PubMed Central. Coevolution of venom function and venom resistance in a rattlesnake predator and its squirrel prey
Venom resistance alone does not determine whether a squirrel survives a snake encounter. Stressed squirrels in poor body condition have lower venom resistance, but they also behave more cautiously around snakes, waiting longer before feeding near one. Researchers found that stress acts as a shared physiological trigger: it independently weakens venom resistance and makes squirrels more wary, which may actually protect less-resistant individuals from getting bitten in the first place.11PubMed Central. Physiological Stress Integrates Resistance to Rattlesnake Venom and the Onset of Risky Foraging in California Ground Squirrels
Ground squirrels also have a behavioral trick that borders on remarkable. California ground squirrels flag their tails when they detect a rattlesnake, and they heat their tails while doing so, adding an infrared signal that rattlesnakes can detect through their heat-sensing pit organs. Experiments with a robotic squirrel model showed that when the infrared component was included in the tail display, rattlesnakes shifted from predatory behavior to defensive behavior more readily than when the tail flagged without the heat signal.12PubMed Central. Ground squirrels use an infrared signal to deter rattlesnake predation Crucially, squirrels only add the infrared component when facing rattlesnakes, not when confronting gopher snakes, which lack heat-sensing pits and would not detect it. The squirrels tailor their defense to the specific predator.
Tail-flagging also serves a broader function. It deters snakes from striking, likely because it advertises that the squirrel is vigilant and ready to dodge. And when adult squirrels tail-flag, nearby squirrels become more alert too, which makes the ambush site less profitable for the snake and increases the chance it will leave entirely.13PubMed Central. Ground squirrel tail-flag displays alter both predatory strike and ambush site selection behaviours of rattlesnakes
Domestic Cats and Free-Ranging Dogs
In suburban and urban environments, domestic cats are a significant squirrel predator. An analysis of wildlife admitted to rehabilitation and rescue centers across the eastern United States found that eastern gray squirrels were among the three species most commonly injured by domestic cats, alongside eastern cottontails and American robins. Roaming cats injured thousands of animals representing 290 species, with animals common in urban and suburban habitats most vulnerable to attack.14Wildlife Society Bulletin. The role of domestic cats in the admission of injured wildlife at rehabilitation and rescue centers
Free-ranging and feral dogs present a different kind of threat. Unlike wild predators, dogs do not follow the same daily activity patterns, and squirrels have not adjusted their behavior to avoid them. The study of squirrel activity patterns in Mexico and Spain found that while squirrels had very low temporal overlap with wild predators like foxes and martens, they had not shifted their schedules to avoid dogs.7Journal of Zoology. Predation risk in tree squirrels: implications of the presence of free‐ranging dogs The researchers flagged this as a potential conservation problem, because it means squirrels are essentially undefended against a predator type they have not had enough evolutionary time to recognize.
Unusual Predators
Some animals that eat squirrels are not the ones you would expect. Alligator snapping turtles, the massive freshwater turtles found in the southeastern United States, are primarily aquatic but will eat virtually anything they can get. Stomach contents from alligator snapping turtles in Arkansas and Louisiana included squirrel remains, along with armadillos, opossums, and feral hogs, none of which had been reported as prey for these turtles before. The researchers concluded that alligator snapping turtles are opportunistic scavengers capable of consuming a surprisingly wide variety of species.15Southeastern Naturalist. Food Habits of Macrochelys temminckii (Alligator Snapping Turtle) from Arkansas and Louisiana Whether these turtles actively caught squirrels or scavenged carcasses that ended up in the water is unclear, but either way, squirrel remains ended up inside a turtle.
Large wading birds like great blue herons occasionally take juvenile squirrels as well. Weasels, fishers, and wolverines are additional mammalian predators in northern forests, though they tend to get less research attention than the species listed above. In tropical regions, various snakes beyond rattlesnakes prey on squirrels, including large constrictors.
Alarm Calls and How Squirrels Identify Threats
Squirrels do not simply run when they detect a predator. Many species produce alarm calls that alert other squirrels, and there has been a long-running scientific debate about whether these calls are predator-specific. Juvenile Belding’s ground squirrels learn to respond to two different alarm call types shortly after they first emerge from their burrows at about one month of age: whistles that warn of aerial predators and trills that warn of threats approaching on the ground.16PubMed Central. Alarm calls elicit predator-specific physiological responses These are not just different behaviors; the physiological stress response differs depending on which call the squirrels hear, suggesting the calls convey genuinely distinct information.
Red squirrels were initially thought to have a similar system, with one early report suggesting they produce a tonal “seet” call for aerial predators and a broadband “bark” for ground predators. Follow-up research, however, found little support for that clean division. Instead, red squirrels produced both call types together in mixed bouts directed at predators of all classes, as well as at non-predatory species and even other squirrels.17Animal Behaviour. Predator-associated vocalizations in North American red squirrels, Tamiasciurus hudsonicus: are alarm calls predator specific? So while some squirrel species appear to have genuinely referential alarm calls, others seem to produce a more general “danger” signal. The picture varies across species and likely depends on the predator community each squirrel lineage evolved alongside.
When Squirrels Are the Predators
Squirrels are primarily herbivores, eating seeds, nuts, fungi, and the occasional insect. But some species also prey on bird nests, and in certain ecosystems this role matters quite a lot. American red squirrels are well-documented nest predators of songbirds, eating eggs and nestlings when they find them. On the islands of Haida Gwaii in British Columbia, researchers compared nest predation rates on islands with and without introduced red squirrels. Where squirrels were present, they added a new predation pressure on forest-nesting birds on top of what native corvids already imposed.18Oikos. Nest predation in forest birds: influence of predator type and predator’s habitat quality
In the mountains of the northeastern United States, tree masting events drive red squirrel populations upward, and those squirrels expand their range to higher elevations in good seed years. Their elevational distribution roughly doubled following a large mast event. As squirrel numbers rose at high elevations, daily nest survival of three songbird species tended to decline.19Diversity and Distributions. Boom and bust: the effects of masting on seed predator range dynamics and trophic cascades The squirrels’ role as both seed predator and bird nest predator makes them a pivotal species in these forest food webs.
Masting, Population Booms, and the Predation Cycle
The availability of tree seeds has an outsized influence on how many squirrels are around for predators to eat. Masting, the synchronized production of a bumper crop of seeds by trees across a wide area, drives squirrel populations in ways that cascade through the whole predator community. The traditional view held that squirrel populations lagged behind mast events: seeds fall, squirrels eat well, then breed, and numbers rise the following year. This lag was thought to be key to how masting works as a reproductive strategy for the trees, because predators are always a step behind the food supply.
That tidy picture took a hit when researchers discovered that both American red squirrels and Eurasian red squirrels anticipate mast events and begin breeding before the seeds actually fall, increasing their reproductive output in advance of the resource pulse.20PubMed. Anticipatory reproduction and population growth in seed predators This eliminates the population lag thought to be universal in these systems. How squirrels detect an incoming mast before the seeds are ready remains somewhat mysterious, though cues from developing flower buds and cones are suspected.
For predators that depend on squirrels, masting matters too. When squirrel populations spike, goshawks take more squirrels. When a mast failure causes squirrel numbers to crash, predators like owls and martens must shift to other prey. The goshawk study in England found that annual variation in squirrel kills tracked spruce masting frequency, with goshawks taking far more squirrels in productive years.1Biological Conservation. Predation of red squirrels by northern goshawks in a conifer forest in northern England: can this limit squirrel numbers and create a conservation dilemma? Despite this, the researchers concluded that goshawk predation was unlikely to limit squirrel populations, because the predation rate would have to exceed 50% of the population to push growth to zero, and it was nowhere close to that level.
How Pine Martens Changed the Game in Britain and Ireland
One of the more unexpected stories in squirrel predation involves what happened when pine martens started recovering in Ireland and Scotland. Grey squirrels, an invasive species from North America, have been displacing native red squirrels across Britain and Ireland for over a century. The conventional approach to the problem involved trapping and culling grey squirrels, with limited success. Then pine marten populations began bouncing back from historical lows, and something striking happened.
Where pine martens recolonized, grey squirrel occupancy dropped sharply. Red squirrel occupancy, meanwhile, increased. Researchers found that the impact of pine marten predation was highly asymmetrical: grey squirrels were strongly negatively affected, while red squirrels benefited indirectly from the predator’s presence.21PubMed Central. The enemy of my enemy is my friend: native pine marten recovery reverses the decline of the red squirrel by suppressing grey squirrel populations Pine marten predation effectively reversed the outcome of competition between the two squirrel species.
Why the lopsided effect? Grey squirrels spend more time on the ground than red squirrels and are heavier and slower in the canopy. They also did not evolve alongside pine martens and lack the anti-predator behaviors that red squirrels have developed over thousands of years of coexistence. The finding has reshaped conservation strategy in Britain and Ireland, where pine marten recovery is now actively encouraged as a natural form of grey squirrel control, supplementing or even replacing costly trapping programs. It is a rare case in wildlife management where a predator’s appetite solves a conservation problem that human intervention had been struggling with for decades.