Many wonder if common rodents like mice and rats hibernate during colder months. This article explores whether these animals truly enter a deep sleep and reveals the actual strategies they employ to endure winter.
Understanding True Hibernation
True hibernation involves a profound physiological transformation allowing certain animals to survive periods of extreme cold and food scarcity. During this state, an animal’s metabolic rate significantly decreases, sometimes to as little as 1% of its normal rate. Body temperature plummets, often nearing ambient temperatures, and can even drop below freezing in some species.
This deep dormancy also includes a drastic reduction in heart rate. Breathing becomes shallow and infrequent. Such prolonged periods of inactivity, lasting weeks or even months, enable true hibernators like ground squirrels, bats, and hedgehogs to conserve energy without needing to forage.
Mice and Rats Do Not Hibernate
Contrary to popular belief, mice and rats do not undergo true hibernation. These rodents remain active throughout the winter, adapting their behaviors and physiology to survive the cold. They cannot sustain the extreme physiological changes characteristic of true hibernators, such as drastically lowered body temperatures for extended periods. Their metabolic slowdowns are not as profound or long-lasting as those seen in animals like groundhogs or bats.
Mice and rats maintain a relatively high metabolic rate compared to true hibernators, requiring them to continuously seek food sources. While their activity might shift to adapt to colder temperatures, they do not enter a state where waking is difficult or requires significant rewarming. This constant need for energy means they must actively forage and find shelter throughout the winter months.
How They Survive Winter
Since mice and rats do not hibernate, they rely on behavioral adaptations and physiological adjustments to endure winter. A primary strategy involves seeking warm, insulated shelters away from the cold. They often move into human dwellings, barns, or other structures, utilizing small openings to gain entry. In natural environments, they might burrow underground, use hollow logs, or find refuge in dense vegetation.
Another critical survival tactic is caching food. Beginning in autumn, rats and mice actively collect and store food, such as grains, seeds, and nuts, in hidden locations. This stockpiling ensures a reliable food supply when foraging becomes challenging due to snow or extreme cold. Additionally, these social animals often huddle together in groups, sharing body heat to conserve energy and maintain warmth.
Mice and rats also engage in daily torpor, distinct from true hibernation. This involves a brief, shallow reduction in body temperature and metabolic rate, typically lasting a few hours. They can lower their body temperature to around 68°F (20°C) during these periods, conserving energy during inactive times, especially when food is scarce or temperatures are low. This short-term energy-saving mechanism allows them to reduce their energy expenditure without committing to the prolonged, deep physiological changes of true hibernation.