Turtles, like many other cold-blooded animals, have developed strategies to survive harsh environmental conditions, including cold winters. Many species go underground, but this period of dormancy is not true hibernation. Instead, it is a distinct process called brumation. Brumation allows turtles to endure periods of low temperatures and limited food availability.
Understanding Turtle Dormancy
Brumation is a state of inactivity and slowed metabolism that reptiles enter in response to environmental cues, primarily decreasing temperatures and shorter daylight hours. This differs from true hibernation, which is a more profound state of dormancy observed in warm-blooded mammals. Unlike hibernating mammals that rely on stored fat and experience drops in body temperature and consciousness, brumating turtles maintain a less extreme metabolic suppression. They may occasionally awaken to drink water or reposition themselves, especially if temperatures temporarily rise.
Why Turtles Go Underground
Turtles seek refuge underground for brumation due to the advantages this environment provides for their survival. The soil acts as a natural insulator, shielding them from extreme cold temperatures. Underground locations offer a more stable temperature, experiencing fewer fluctuations than the external environment, which helps maintain their body temperature within a safe range. The subterranean environment also offers protection from predators, which might otherwise target inactive turtles. The moisture content in the soil helps prevent desiccation, a risk for turtles during extended periods of inactivity.
How Turtles Survive Underground
During underground brumation, a turtle’s body undergoes physiological changes to conserve energy and endure prolonged periods without food or consistent oxygen. Their metabolic rate slows dramatically, reducing energy expenditure. Heart rate also decreases significantly. Breathing nearly ceases, with some aquatic species absorbing oxygen directly from the water through their skin and cloaca.
When oxygen becomes scarce, turtles can switch to anaerobic respiration, producing energy without oxygen. This process generates lactic acid, but turtles possess adaptations to buffer and tolerate its buildup, utilizing compounds from their shell and bones. They rely on stored energy reserves, primarily glycogen, rather than fat reserves like hibernating mammals. This suite of adaptations, including tolerance to low oxygen, allows them to survive for several months.
Factors Influencing Underground Brumation
Environmental cues, primarily declining temperatures and shorter daylight hours, signal the onset of winter, prompting turtles to seek suitable brumation sites. Preferred locations vary by species; terrestrial turtles often dig into soft soil, leaf litter, or existing burrows, while aquatic turtles may burrow into the mud at the bottom of ponds, lakes, or rivers. Not all turtle species brumate underground; some aquatic species remain submerged in water bodies, and turtles in warmer climates may not brumate at all. The duration of brumation can vary based on geographical location and species.