Lizards are ectothermic, meaning they depend on external heat sources to regulate their body temperature. This reliance presents a challenge during winter, as temperatures drop and food sources become scarce. To survive these harsh conditions, lizards employ specific strategies to endure periods of cold and limited resources.
Lizard Winter Strategies
During winter, many lizard species enter a state of dormancy known as brumation. This period involves a slowdown of their metabolic processes and a reduction in activity. Brumation is a necessary adaptation that allows lizards to conserve energy when environmental conditions are unfavorable, primarily due to cold temperatures and reduced food availability.
Lizards typically seek out sheltered locations to undergo brumation, minimizing their energy expenditure and increasing their chances of survival. Common places they choose include underground burrows, rock crevices, and hollow logs. These locations offer insulation against extreme cold, providing a stable microclimate for their dormant period.
Understanding Brumation
Brumation in lizards is a distinct physiological process, differing from the true hibernation observed in mammals. While both involve a state of inactivity to conserve energy, hibernating mammals experience a profound drop in body temperature and a more dramatic reduction in metabolic rate. Lizards in brumation, however, maintain a relatively stable internal body temperature, influenced by their environment, and may periodically rouse themselves.
During brumation, a lizard’s metabolism slows significantly, reducing its need for food and energy. Their heart rate and breathing rate decrease substantially, and digestion almost ceases. This metabolic depression allows them to survive extended periods without eating, living off stored energy reserves such as glycogen.
Temperature and daylight hours are key environmental cues that trigger the onset and conclusion of brumation. As days shorten and temperatures drop in the fall, lizards instinctively prepare for this dormant phase. They seek out stable microclimates that remain above freezing, usually between 40 and 50 degrees Fahrenheit, to prevent their bodies from freezing.
Unlike true hibernators, lizards in brumation may occasionally wake up. They might emerge briefly to drink water, which is important for preventing dehydration, before returning to their dormant state.
Variations in Winter Behavior
Lizard winter behavior is not uniform across all species or geographical locations. It varies based on factors such as climate, species-specific adaptations, and local environmental conditions. Lizards in tropical regions, for instance, may not undergo brumation at all. Instead, they might experience short periods of reduced activity during cooler or drier seasons, a process sometimes referred to as aestivation if it’s a response to extreme heat.
Species-specific adaptations also play a role in how lizards cope with cold. Some species have evolved unique physiological traits to tolerate colder temperatures, such as the common side-blotched lizard, which can have glucose in its blood that acts as an antifreeze. The viviparous lizard, found in subarctic regions, can even survive brief periods of sub-zero temperatures by entering a “supercooled” state or tolerating ice crystal formation in their bodies, though this is rare among lizards.
Changing winter patterns, influenced by climate shifts, can impact brumation cycles and lizard survival. Milder winters or unseasonable thaws can disrupt the natural cues for entering and exiting brumation, potentially leading to physiological stress or increased vulnerability. This highlights the delicate balance between a lizard’s adapted winter strategies and the environmental conditions they encounter.