Q. Consider the following:

1. Bats
2. Bears
3. Rodents

The phenomenon of hibernation can be observed in which of the above kinds of animals? (UPSC Prelims 2014)
Answer: 1, 2 and 3
Notes: The correct answer is [C] 1, 2 and 3. Hibernation is a state of minimal activity and metabolic depression in endotherms, characterized by low body temperature, slow breathing and heart rate, and low metabolic rate.

• Bats (Statement 1 – Correct): Many species of bats in temperate regions hibernate during winter when their primary food source (insects) is unavailable. They retreat to caves or mines (hibernacula) where temperatures remain stable, allowing them to conserve energy for several months.
• Bears (Statement 2 – Correct): Bears are famous hibernators. While there has been some scientific debate because their body temperature doesn't drop as drastically as "true hibernators" (like ground squirrels), they undergo a prolonged period of dormancy without eating, drinking, or excreting waste, which fits the broader biological definition of hibernation.
• Rodents (Statement 3 – Correct): This group includes some of the most classic examples of hibernators. Ground squirrels, woodchucks (groundhogs), and dormice are well-known for entering deep hibernation. During this state, a rodent's heart rate can drop from several hundred beats per minute to just a few.

It is important to distinguish hibernation (winter dormancy) from aestivation (summer dormancy). While hibernation helps animals survive extreme cold and food scarcity in winter, aestivation is a survival strategy for extreme heat and arid conditions, commonly seen in some reptiles and amphibians.