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How does day length influence dormancy in animals and plants?

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The image shows a group of Virginia big-eared bats sleeping upside down in a dark cavern. — Dormancy Virginia big-eared bats (*Corynorhinus townsendii virginianushibernating*) are true hibernators, entering a state close to death for much of the winter.

Day length, or photoperiod, serves as a critical environmental cue that helps both plants and animals anticipate and prepare for seasonal changes by inducing dormancy.

Plants

In temperate zones, many woody plants use the shortening of day length at the end of the growing season as a signal to cease shoot growth and form resting buds, which protect the stem from winter conditions. This process often involves the formation of inhibitor compounds, such as abscisic acid, which are transmitted to the plant's apex to halt development. Conversely, the lengthening days of spring can trigger budbreak, allowing growth to resume.1

Animals

For many animals, particularly insects and mites, changes in day length are a primary trigger for diapause, a state of suspended development characterized by reduced metabolic activity. In vertebrates, such as hibernating mammals, shorter days—often in conjunction with temperature drops and food scarcity—influence internal mechanisms that signal the onset of hibernation. While these responses are often genetically determined, they allow organisms to survive periods of environmental stress by synchronizing their life cycles with predictable seasonal patterns.2345