Yes, squirrels carry ticks, and they carry a lot of them. The average gray squirrel hosts around 150 larval ticks at a time, making them one of the more heavily parasitized backyard animals. For comparison, a typical mouse carries about 25 larval ticks, while an opossum averages around 250. Squirrels also serve as hosts for several tick species that can transmit diseases to humans, which makes them more than just a nuisance in your yard.
Tick Species That Feed on Squirrels
Several tick species use squirrels as hosts, but squirrels have their own dedicated parasite: the squirrel tick. This species feeds primarily on squirrels and lives in or near their nests. It’s found mainly in the northeastern United States and will occasionally latch onto other small mammals like raccoons and rabbits, but squirrels are its preferred host.
Squirrels also pick up the same tick species that bite humans. In the eastern U.S., deer ticks (also called blacklegged ticks) feed on squirrels during their larval and nymphal stages. On the West Coast, the western blacklegged tick uses squirrels as hosts. These are the same ticks responsible for transmitting Lyme disease and other infections to people. Squirrels don’t bring ticks directly to you in most cases, but they help sustain tick populations in your neighborhood by feeding large numbers of immature ticks that later mature and seek out new hosts, including humans and pets.
Squirrels as Disease Reservoirs
Carrying ticks is one thing. What makes squirrels especially relevant to human health is their ability to harbor and transmit disease-causing bacteria to those ticks. A study of 222 western gray squirrels in California found that 30% were infected with the bacterium that causes Lyme disease. In lab trials, infected squirrels passed the bacterium to up to 86% of immature ticks that fed on them. Even months after initial infection, squirrels continued transmitting the pathogen, infecting 47% of feeding ticks four months later. That makes them highly effective reservoir hosts, meaning they don’t just passively carry ticks but actively spread disease through the tick population.
Not all squirrel species play the same role. Western gray squirrels appear to be particularly competent reservoirs for Lyme disease in California, where they may be more important to the transmission cycle than other small mammals. In the eastern U.S., white-footed mice have traditionally been considered the primary Lyme reservoir, but gray squirrels still contribute to the cycle by feeding enormous numbers of larval ticks.
Diseases Linked to Squirrel-Fed Ticks
Lyme disease gets the most attention, but it isn’t the only concern. Squirrel ticks and woodchuck ticks are primary carriers of Powassan virus, a rare but serious tick-borne illness that can cause brain inflammation. Unlike Lyme disease, which typically requires a tick to feed for 36 to 48 hours before transmission, Powassan virus can be transmitted in as little as 15 minutes of tick attachment. The squirrel tick is one of the main vectors for lineage I of this virus.
A study examining ticks collected from red squirrels in Warsaw’s city parks found lower rates of common tick-borne pathogens. About 2.5% of ticks pulled from those squirrels tested positive for the Lyme disease bacterium, and only one tick out of 350 carried a parasite that destroys red blood cells. These numbers are relatively low compared to ticks found on some other hosts, but they confirm that even urban squirrels contribute to the circulation of tick-borne diseases.
When Tick Loads Are Highest
Squirrels carry the most ticks during spring and summer, which aligns with the general peak of tick activity. Research on ground squirrels in temperate grasslands found that tick loads were significantly higher in spring and summer compared to autumn. This seasonal pattern matters because it overlaps with the time of year when people spend the most time outdoors, increasing the chances that ticks that fed on squirrels will encounter humans or pets.
Squirrels that are weakened or in poor health may carry even heavier tick burdens. Researchers observed interactions between season and the animal’s overall condition, with some hosts accumulating unusually high tick loads heading into autumn. Heavily parasitized squirrels effectively become amplifiers for the local tick population, producing more fed ticks that drop off into your yard, garden beds, or leaf litter.
What This Means for Your Yard
If you see squirrels regularly in your yard, you’re looking at animals that collectively drop hundreds or thousands of immature ticks into the surrounding environment each season. Those ticks molt into their next life stage and begin questing for a new host, which could be you, your children, or your dog. Squirrels are harder to exclude than some other wildlife because they’re agile climbers and persistent foragers, but a few practical steps reduce the risk.
Keeping leaf litter cleared, maintaining short grass near play areas and walkways, and creating a 3-foot wood chip or gravel barrier between your lawn and wooded edges all reduce tick habitat. Bird feeders attract squirrels, and the ground beneath feeders becomes a hotspot for tick drop-off. If you’re in a Lyme-endemic area, relocating feeders away from high-traffic parts of your yard helps. Treating your pets with tick preventives is also important, since dogs and cats can pick up squirrel-dropped ticks and bring them indoors.
You won’t catch a tick-borne disease directly from a squirrel. The risk comes from the ticks they leave behind, which is why managing your outdoor environment matters more than managing the squirrels themselves.