Difference Between Torpor and Hibernation

Introduction

Nature has various mechanisms in place to safeguard plants and animals from environmental hazards. Many mammal and bird species temporarily abandon euthermia (normal body temperature) and substantially drop their body temperature and energy expenditure during periods of cold weather, drought, or a scarcity of food resources, permitting them to live in harsh environmental conditions.

Torpor refers to the hypometabolic condition linked with low body temperatures in eutherms. There are two types of torpor:

• Daily torpor
• Hibernation

What is Torpor?

Torpor is a hypometabolic condition characterised by low body temperature. It allows animals to survive periods of harsh environmental circumstances. Torpor can be short-term (daily) or long-term (hibernation), depending on the duration of the hypometabolic state.

Daily torpor lasts fewer than 24 hours. Torpor characteristics vary according to the species' geographical area and body mass.

Torpor is a survival mechanism employed by animals (heterotherms) to get through the winter. It also decreases body temperature, respiratory rate, heart rate, and metabolic rate. It is an involuntary state that an animal enters in response to environmental conditions. It lasts for brief periods of time, sometimes only throughout the night or day, depending on the animal's feeding habits.

During their active phase of the day, these animals maintain regular body temperature and physiological rates. However, while inactive, they fall into a deeper sleep, allowing them to preserve energy and survive the winter.

Torpor arousal lasts around one hour and is characterised by severe shaking and muscle contractions. It loses energy, but this is countered by the amount of energy saved in the torpid stage. This state is caused by the ambient temperature and the availability of food. Bears, raccoons, and skunks are all "light hibernators" who use torpor to get through the winter.

What is Hibernation?

Hibernation is a type of managed hypothermia that helps animals conserve energy during extended periods of low temperatures. It can last several days to months. The hibernating animals do not eat and dwell at higher average latitudes. They store body fat throughout the warm months and use it as an energy reserve during the hibernation season.

It is a voluntary state that animals enter to conserve energy, survive when food is short, and reduce their exposure to the elements during the cold winter months. It is a physiological state characterised by low body temperature, sluggish breathing, heart rate, and metabolic rate. Depending on the species, it can last a few days, weeks, or months.

Before entering hibernation, animals typically store fat to help them survive the long winter. During hibernation, they may wake up briefly to feed, drink, or defecate, but they generally stay in this low-energy state for as long as possible. Arousal from hibernation takes several hours and depletes much of an animal's stored energy.

True hibernation was originally restricted to a selected group of creatures, including deer mice, ground squirrels, snakes, bees, woodchucks, and some bats. However, the term has now been extended to encompass some animals that adopt a lighter level of activity known as torpor.

Main Differences: Torpor and Hibernation

• Everyday heterotherms are smaller than hibernators. Animals that hibernate are typically larger than everyday heterotherms.
• Torpor's average minimum metabolic rate is 35% of the baseline metabolite rate in daily heterotherms. In contrast, during hibernation, the average lowest metabolic rate is 6% of the basal metabolite rate.
• Torpor is triggered by food availability and ambient temperature, both of which suggest the need for energy conservation. On the other hand, hormonal changes and changes in day duration cause animals to enter a state of hibernation.
• In terms of geographical distribution, daily heterotherms reside in lower latitudes on average. Meanwhile, hibernators reside in higher latitudes.

Comparison Table

Conclusion

Both torpor and hibernation are methods used by animals to live in severe environments, and they differ greatly in duration, metabolic rates, regulatory systems, and voluntary nature. Torpor, often known as "light hibernation," is an involuntary, short-term hypometabolic state that lasts only a few nights or days. It is distinguished by a metabolic rate of approximately 35% of the baseline, which is regulated by circadian rhythms and driven by environmental stimuli such as temperature and food availability. Hibernation, on the other hand, is a prolonged hypothermic condition lasting several months, weeks, or days, defined by a metabolic rate of approximately 6% of the baseline and produced by hormonal changes and day length variations. Understanding these contrasts is critical for recognising the many survival methods established by animals to cope with harsh situations.