Hibernaculum (zoology)

A hibernaculum plural form: hibernacula (Latin, "tent for winter quarters") is a place in which a creature seeks refuge, such as a bear using a cave to overwinter. The word can be used to describe a variety of shelters used by many kinds of animals, including insects, toads, lizards, snakes, bats, rodents, and primates of various species.

A common frog emerging from its hibernation under a clump of vegetation, which functions as its hibernaculum

Gray bats congregating and using the entirety of a natural cave as a hibernaculum

Insects range in their size, structure, and general appearance but most use hibernacula. All insects are primarily exothermic. For this reason, extremely cold temperatures, such as those experienced in the winter season, outside of tropical locations, cause their metabolic systems to shut down; long exposure may lead to death. Insects survive colder winters through the process of overwintering, which occurs at all stages of development and may include migration or hibernation for different insects, the latter of which must be done in hibernacula. Insects that do not migrate must halt their growth to avoid freezing to death, in a process called diapause. Insects prepare to overwinter through a variety of mechanisms, such as using anti-freeze proteins or cryoprotectants in freeze-avoidant insects, like Soybean aphids. Cryoprotectants are toxic, with high concentrations only tolerated at low temperatures. Thus, hibernacula are used to avoid sporadic warming and the risk of death due high concentrations of cryoprotectants at warmer temperatures. Freeze-tolerant insects, like second-generation corn-borers, can survive being frozen and therefore, undergo inoculative freezing. Hibernacula range in size and structure depending on the insects using them.

However, insect hibernacula are generally required to be:

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