Ületalitlus

Ületalitlus is a Finnish term that translates to "winter lethargy" or "hibernation" in English, though it's not a true hibernation in the same sense as seen in some mammals. It refers to a state of reduced metabolic activity and torpor that some animals enter during the cold, dark winter months to conserve energy when food is scarce. This state is characterized by a lower heart rate, slower breathing, and a drop in body temperature, although typically not as drastic as in true hibernators.

Animals that exhibit ületalitlus may not remain completely inactive but will enter periods of deep sleep interspersed with brief awakenings, often to urinate or defecate. This allows them to survive long periods without eating. The depth and duration of ületalitlus vary among species. For instance, hedgehogs and bats undergo a more profound state of torpor, while animals like bears, which are often described as hibernating, actually experience a lighter form of dormancy where they can be more easily roused.

The triggers for entering ületalitlus are primarily environmental cues such as falling temperatures, reduced daylight hours, and a scarcity of food sources. Physiological changes within the animal also play a crucial role in initiating and maintaining this state. Animals prepare for ületalitlus by accumulating fat reserves during the warmer months, which then serves as their primary energy source during the period of inactivity. Successful survival through ületalitlus is critical for many species' reproductive success in the following spring.