Ticks are often assumed to only pose a threat during warmer months, but their activity is not entirely seasonal and can persist throughout the year. While some species enter a state of dormancy during winter, others, like the blacklegged tick, can become active on any mild day above freezing. A specialized species, the Winter Tick, operates almost exclusively during the colder months, posing a significant threat to wildlife.
How Common Ticks Survive Cold Weather
Common ticks, such as the blacklegged tick (Ixodes scapularis), do not die off with the first frost. They enter a quiescent state, or behavioral diapause, typically sheltering in leaf litter or under the soil. This leaf layer creates a protective microclimate that insulates them from the harsh air temperatures above. Snowfall further enhances survival by providing additional insulation to the ground environment where ticks hide.
Adult blacklegged ticks, the primary concern in late fall and early spring, can become active and quest for a blood meal once temperatures rise above 35°F to 40°F (about 2°C to 4°C). During unseasonably warm spells in January or February, these parasites emerge from shelter, posing a risk to humans and pets venturing outdoors. Their ability to quickly resume activity during mild winter days demonstrates that tick exposure is a year-round consideration.
The Unique Life Cycle of the Winter Tick
The Winter Tick (Dermacentor albipictus) displays a life cycle entirely synchronized with the cold season. Unlike other species that use multiple hosts, the Winter Tick is a “one-host” species. This means all three active stages—larva, nymph, and adult—feed on the same individual animal, remaining attached throughout the fall and winter.
Larvae hatch in late summer and quest in large clusters on vegetation from late August through the fall. Once a host brushes past, the larvae attach and remain on the animal through subsequent molting stages. They feed and molt into nymphs around October and November, and then into adults between January and March. Engorged adult females drop off the host in late winter or early spring to lay eggs on the ground, completing their annual cycle.
The preferred hosts for the Winter Tick are large ungulates, including moose, elk, caribou, and deer, though they can also infest cattle and horses. Moose are particularly susceptible to massive infestations, sometimes carrying over 100,000 ticks, which can lead to severe anemia and death. The constant irritation causes moose to rub off their hair, leading to the condition known as “ghost moose syndrome,” which compromises their thermal regulation during winter.
Key Differences in Tick Behavior and Risk
The difference between the Winter Tick and common ticks lies in their active feeding period and implications for human health. Common ticks, like the blacklegged tick, are sporadically active in winter, relying on brief, above-freezing temperatures to find a host. Their main threat to humans is the transmission of pathogens, such as the bacteria that cause Lyme disease, facilitated by their multi-host feeding strategy.
In contrast, the Winter Tick is consistently active throughout the fall and winter, but its main hosts are large wild mammals, not humans. Because it is a one-host tick, the likelihood of it transmitting disease to humans or between different animals is significantly reduced. The Winter Tick is primarily a wildlife management concern, causing hair loss and mortality in ungulates.
Prevention Strategies for Year-Round Tick Exposure
Since common ticks can be active during mild winter spells, a year-round approach to prevention is necessary. When planning outdoor activities, pre-treat clothing with products containing 0.5% permethrin, which kills ticks upon contact. Wearing long pants tucked into socks and using EPA-registered repellents on exposed skin, such as those containing DEET, further minimizes the risk of attachment.
Protection for pets is also important, as they can carry ticks into the home environment. Veterinarians often recommend using year-round oral or topical tick prevention products for dogs and cats, rather than stopping treatment in colder months. After spending time outdoors, a thorough body check for ticks is recommended, and placing clothing in a hot dryer for at least ten minutes will effectively kill any ticks still clinging to the fabric.