Ticks do not truly go dormant like hibernating bears. Instead, they enter a state of reduced activity, often called quiescence, where their metabolism slows considerably. This allows them to conserve energy and survive periods of unfavorable conditions. While activity decreases in colder months, they remain responsive to environmental changes and can become active on warmer days, posing a year-round risk.
How Ticks Survive Unfavorable Conditions
Ticks employ several biological mechanisms to survive cold, dry, or hot periods. One strategy is diapause, a state of suspended development or activity triggered by environmental cues like day length and temperature. Diapause can be developmental, halting growth, or behavioral, suppressing host-seeking. This allows ticks to delay their life cycle stages until conditions are more suitable.
Ticks also seek shelter to protect themselves from extreme temperatures and desiccation. They commonly hide in leaf litter, soil, and even within tree bark crevices. Snow cover insulates them, acting as a protective barrier against freezing. Some tick species can even withstand surprisingly low temperatures, with certain blacklegged ticks surviving down to -7 degrees Fahrenheit (-21.7 degrees Celsius) by drawing water out of their cells to prevent ice crystal formation.
Different life stages exhibit varying survival tactics. Larval and nymphal ticks may remain inactive until temperatures and day length increase substantially. Adult ticks, particularly blacklegged ticks, are often a concern in colder months as they can become active on milder winter days. Ticks can also find warmth and sustenance by remaining attached to a host animal throughout the winter.
Environmental Triggers for Tick Activity
External environmental factors play a significant role in determining when ticks are active. Temperature is a primary driver, with many tick species, including adult blacklegged ticks, becoming active when temperatures rise to 35-40 degrees Fahrenheit (4 degrees Celsius) or above. Even during winter, unseasonably warm spells can trigger ticks to emerge from their sheltered spots and begin questing for a host.
Humidity is another important factor for tick survival and activity. Ticks require high humidity, ideally between 80% and 90%, to prevent dehydration. Low humidity, especially prolonged dry air, can significantly reduce tick survival and host-seeking activity. Ticks are often found in moist environments like wooded areas, tall grasses, and leaf litter, which help them maintain moisture.
While ticks can be active in winter, their host-seeking activity is generally reduced compared to warmer months. However, ticks can still be found questing in winter, even under snow, particularly during mild periods. The overall climate, including factors like temperature and humidity, influences tick populations and their behavior.
Implications for Human Safety
Since ticks can be active even in winter, year-round tick awareness and prevention are important. The risk of encountering ticks extends beyond just the warmer seasons, especially in areas with milder winters or during unseasonably warm periods.
Ticks are commonly found in wooded areas, tall grasses, brushy fields, and leaf litter, which provide the moisture and cover they need. They do not fly or jump; instead, they climb onto vegetation and wait for a host to brush against them.
Preventive measures include checking for ticks after spending time outdoors, wearing protective clothing such as long sleeves and pants, and using tick repellents containing at least 20% DEET, picaridin, or oil of lemon eucalyptus. Maintaining yards by regularly mowing lawns and removing leaf litter can also help reduce tick habitats. Consulting with a veterinarian for year-round tick prevention for pets is also recommended, as pets can bring ticks indoors.