Ants are a highly successful group of social insects whose survival is intrinsically linked to the temperature of their environment. Unlike mammals, these creatures cannot generate their own internal body heat, making them sensitive to seasonal changes. When the weather is warm, ants are easily observed foraging and building nests, but once the cold arrives, their activity drops significantly. This change in behavior is a necessary survival mechanism that allows entire colonies to endure the harsh conditions of winter until spring returns.
Why Temperature Controls Ant Activity
Ants are classified as ectotherms, meaning their body temperature and metabolic functions are regulated entirely by the surrounding environment. When temperatures are optimal, typically between 25°C and 35°C (77°F and 95°F) for many common species, ants are at their most active, moving quickly and foraging efficiently.
As the air temperature drops, the chemical reactions within the ant’s body slow down dramatically, reducing their movement and energy expenditure. Foraging activity effectively stops once the ambient temperature falls below approximately 10°C (50°F), as movement becomes sluggish and inefficient. This limitation means that outdoor tasks become impossible, forcing the colony into a survival state.
The Winter State of Dormancy
To survive prolonged cold periods, ants enter a specialized state of metabolic suppression known as diapause. This biological process is triggered by environmental cues, primarily the shortening of daylight hours and the sustained drop in temperature in late autumn. Diapause allows the colony to conserve energy and survive for months without food or water intake beyond what is stored in the nest.
Physiologically, ants prepare by building up fat bodies to serve as internal energy reserves throughout the winter. Some species also generate cryoprotectants, such as glycerol, a type of alcohol that acts as a natural antifreeze to prevent the formation of damaging ice crystals. During this period, the queen stops laying eggs, and the larvae stop growing, halting all reproductive and developmental activity. This collective slowing allows them to remain in a state of deep rest until the warmth of spring signals them to awaken.
Where Ants Relocate for the Cold
When cold weather arrives, the entire ant colony undertakes a relocation effort to find a thermally stable environment. Workers move the colony deep underground, often excavating chambers several feet below the surface to get past the frost line. The soil acts as an effective natural insulator, keeping temperatures relatively constant and above freezing, regardless of the air temperature above ground.
Once settled in these subterranean chambers, the ants form a tight cluster around the queen and any remaining brood. This behavior helps maintain a stable, slightly warmer microclimate through collective body heat. They remain motionless in this clustered state throughout the winter, relying on stored energy reserves until the soil temperature begins to rise. While most ant species retreat into the earth, certain species, like carpenter ants, may seek shelter inside dead wood or within the walls and foundations of human structures, finding similar insulated conditions.