Brumation is a natural physiological process where lizards, along with other cold-blooded animals, enter a seasonal period of reduced activity and metabolic function. This state of dormancy allows these ectotherms to survive periods when environmental conditions become unfavorable, such as during cold weather or drought. The cycle is an inherited survival adaptation that ensures energy conservation when food sources are scarce and temperatures are too low for active foraging and digestion. For many lizard species in temperate and subtropical regions, brumation is a necessary part of their annual rhythm, preparing them for the breeding season that follows their emergence.
Brumation Versus Hibernation
The state of dormancy lizards enter is correctly termed brumation, which differs significantly from the true hibernation observed in mammals. Lizards are ectotherms, meaning their body temperature is regulated by their external environment, while hibernating mammals are endotherms. During true hibernation, a mammal’s body temperature and metabolic rate drop profoundly, often resulting in a deep, sustained unconsciousness.
A brumating lizard’s metabolic rate slows down substantially, reducing its heart rate and respiration, but the animal remains semi-aware. The lizard’s body temperature will generally align with the ambient temperature of its sheltered location. Because reptiles do not enter the same deep, sustained sleep as hibernating mammals, they may wake periodically to move, reposition themselves, or seek water for hydration.
Environmental Triggers and Timing
The onset of brumation in free-ranging lizards is primarily determined by two environmental factors that signal the approaching winter season. The most influential cue is the decrease in ambient temperature, which directly impacts the lizard’s body temperature and metabolic rate. As temperatures consistently drop, the lizard’s ability to efficiently digest food and sustain high levels of activity diminishes, prompting the search for shelter.
The second factor is the reduced photoperiod, or the shortening of daylight hours, which acts as an internal biological clock. This decrease in light exposure, sometimes along with hormonal changes, helps to reinforce the cooling temperatures as a signal for dormancy. Lizard species in temperate zones typically begin brumation in late autumn, usually between October and November, but the exact timing and duration vary depending on the species and local climate.
Preparing for and Entering Brumation
Before a lizard can safely enter the dormant period, it must undergo a specific sequence of behavioral and physiological preparations. As the environmental cues signal the need for dormancy, the lizard will increase its food intake to build up fat reserves, which serve as the primary energy source during the long period without feeding. This pre-brumation phase, often beginning in late summer, involves seeking out nutrient-rich meals to maximize stored resources.
The cessation of feeding several weeks before the onset of cold temperatures is essential, ensuring the digestive tract is fully empty. Since a lizard’s metabolism slows drastically during brumation, undigested food remaining in the stomach or intestines can rot, leading to a fatal bacterial infection. Owners of pet lizards often assist this process by providing warm soaks or gentle belly massages to encourage a final bowel movement.
Once feeding stops and the gut is clear, the lizard actively searches for a secure and insulated location, known as a hibernaculum. This site might be a deep burrow, a rock crevice, a hollow log, or a space beneath leaf litter that offers protection from freezing temperatures and predators. The chosen location must maintain a stable temperature above freezing, ideally between 40°F and 60°F, as temperatures below this range can be lethal to the animal.
The State of Brumation and Emergence
Once settled in its hibernaculum, the lizard’s physiological functions slow to a minimum to conserve the stored energy reserves. The heart rate and breathing rate become significantly reduced, and the lizard enters a state of torpor, minimizing the use of fat stores. This metabolic slowdown allows the lizard to survive without food for the entire brumation period, which can last from a few weeks to several months, depending on the species and the severity of the winter.
The lizard does not enter a complete state of suspended animation, often waking up to reposition itself or briefly emerge on warmer days to drink water. Dehydration is a significant threat during brumation, and maintaining access to water is important for survival. The animal’s body fat reserves are used slowly over time, meaning a healthy lizard should not lose a considerable amount of weight during the dormant period.
The end of brumation is triggered by the reversal of the initial environmental cues: rising ambient temperatures and the lengthening of the photoperiod in the spring. As the weather warms, the lizard begins to stir and eventually leaves its shelter to bask and raise its body temperature, a process that can take several days. The immediate post-brumation period requires a focus on rehydration before any food is offered.
Lizards emerging from brumation often have a renewed appetite and activity level, and for many species, this emergence coincides with the onset of their annual reproductive cycle. Feeding should be reintroduced slowly with easily digestible items to allow the digestive system to reactivate gradually. A healthy brumation cycle stimulates hormonal release for breeding success in the spring.