What term describes a state of reduced metabolic activity in animals, often occurring in winter?

The correct term for a state of reduced metabolic activity in animals that occurs during winter is hibernation. Hibernation is a survival strategy adopted by some animals to cope with extreme cold and scarcity of food during the winter months. During this time, an animal's metabolic rate significantly decreases, allowing it to conserve energy. The body temperature drops, heart rate slows, and many physiological processes are minimized. This adaptation helps animals to survive in conditions where resources are limited.

Other related terms can sometimes cause confusion. Estivation, for example, refers to a similar state of dormancy that occurs during hot and dry periods, primarily in desert animals. Brumation is also a state akin to hibernation but typically applies to reptiles and involves a similar reduction in metabolic rate during colder months. Both of these terms describe different environmental conditions and types of organisms, thus highlighting hibernation's specificity to cold-weather adaptation in certain animals.