As colder months arrive, many people notice the disappearance of lizards from their usual outdoor spots. Unlike mammals, lizards are cold-blooded and rely on their environment to regulate their temperature. This fundamental biological difference means they must employ specialized strategies to survive winter’s chill. Their disappearance is a carefully adapted survival response to the changing seasons.
Lizard Physiology in Cold Weather
Lizards are ectothermic, meaning their body temperature is primarily determined by external sources. This contrasts with endothermic animals, like mammals and birds, which internally regulate their body temperature. This dependency on environmental heat means that cold conditions significantly slow down their metabolism.
When their body temperature falls too low, lizards become sluggish and inactive. Their metabolic rate decreases, making it difficult for them to move quickly, hunt for food, or escape predators. Digestion also becomes problematic at low temperatures; if a lizard has undigested food in its stomach when it gets too cold, the food can rot, potentially leading to illness or death. This necessitates reduced activity and seeking shelter to survive winter.
Brumation: The Reptile Winter Sleep
To survive cold periods, lizards enter a dormant state known as brumation, which is similar to hibernation but distinct. This state is primarily triggered by dropping temperatures and reduced daylight hours. During brumation, a lizard’s metabolic rate significantly decreases, allowing it to conserve energy on stored reserves.
Unlike true hibernation, brumating lizards are not in a deep, continuous sleep; they may occasionally wake up. On warmer winter days, they might emerge briefly to drink water before returning to their dormant state. Lizards typically prepare for brumation by eating more in the autumn to build up fat reserves, which sustain them through inactivity. They also store glycogen, a form of sugar, to provide energy for their muscles.
Common Winter Havens
When winter approaches, lizards seek out specific locations that provide insulation and protection from extreme cold and predators. Natural shelters are frequently utilized, including underground burrows, which some species may dig themselves or use abandoned ones. Rock crevices, piles of fallen logs, and dense leaf litter also serve as suitable hiding spots, offering natural insulation. These locations help maintain a more stable temperature than the fluctuating air outside.
Some lizards may also find refuge in human-made structures, such as cracks in building foundations, sheds, or woodpiles. The chosen havens typically extend below the frost line in regions with severe winters, ensuring the lizard remains in temperatures above freezing. This allows lizards to undergo brumation safely until warmer temperatures signal the arrival of spring.