Newts, like all amphibians, are ectothermic creatures whose internal body temperature mirrors their environment. When colder months arrive, they enter a period of deep dormancy to conserve energy and avoid freezing. Although this winter behavior is often called hibernation, that term is technically inaccurate for cold-blooded animals. Newts enter a specific state of inactivity, distinct from the regulated sleep of true mammalian hibernators, allowing them to endure cold and food scarcity until spring.
Brumation: Newts’ Winter Survival Strategy
The correct scientific term for the winter dormancy observed in newts and other amphibians is brumation. Brumation is a state of metabolic depression that ectotherms enter when temperatures drop significantly. This process is involuntary, driven directly by external cold, unlike the internally regulated process of true hibernation found in warm-blooded mammals.
During brumation, a newt’s body temperature, metabolic rate, and heart rate decrease substantially, but they avoid the continuous, deep sleep characteristic of mammalian hibernation. Brumating newts can be roused more easily and may wake on warmer days to move or drink water. True hibernators, such as ground squirrels, enter a near-comatose state. Newts rely on this slowed metabolism to survive the winter without needing to forage.
Choosing a Winter Retreat
Brumation is triggered primarily by environmental cues, specifically dropping ambient temperatures and the shortening of daylight hours (photoperiod). Newts begin seeking overwintering sites when temperatures consistently fall below 10°C (50°F). The exact location chosen depends on the newt’s life stage and whether it is a terrestrial or aquatic species.
Terrestrial Sites
Terrestrial newts, including the juvenile “eft” stage, seek sheltered, damp, and well-insulated spots on land. They choose sites that provide a stable temperature buffer against extreme cold and allow them to remain moist. They commonly overwinter in locations such as:
- Beneath logs or large rocks.
- Deep leaf litter.
- Within underground root systems.
- Inside old walls, staying below the frost line.
Aquatic Sites
Aquatic newts, such as the North American Eastern Newt, often overwinter directly in their water body. They settle into the soft substrate at the bottom of ponds, streams, or ditches. They may bury themselves slightly in the mud or rest under submerged debris. Viable aquatic sites must be deep enough not to freeze completely solid and must maintain adequate levels of dissolved oxygen.
How Newts Cope with Cold
The physiological changes allowing newts to survive the cold focus on extreme energy conservation and a shift in respiration. During brumation, a newt’s metabolic rate can drop by 70% or more, drastically reducing the energy needed to sustain life. They rely on fat reserves accumulated during warmer months to provide the minimal energy required for bodily functions.
The heart rate and breathing rate slow considerably, aligning with the lowered metabolic demand. Aquatic newts remaining submerged shift their primary breathing method from lungs to cutaneous respiration. This process involves absorbing oxygen directly through the highly permeable skin. This is effective because cold water holds higher dissolved oxygen content. This efficient skin breathing allows them to stay underwater for the entire brumation period without needing to surface.