When it comes to animals and plants, to protect themselves from the environment’s harmful effects they use distinctive mechanisms in nature.
Mainly during drought, cold weather, or depletion of the available food resources. Several bird and mammal species temporarily abandon euthermia and drastically reduce energy expenditure and body temperature.
Through this, they can survive during periods with environmental conditions that are unfavourable. When it comes to hibernation, it is one of the subtypes of torpor. In this article, the main focus is on differentiating torpor and hibernation.
Key Takeaways
- Torpor is a short-term state of reduced metabolic activity, while hibernation is a long-term state of energy conservation.
- Hibernation lasts for weeks or months, whereas inertia can last for hours or days.
- Both torpor and hibernation are survival strategies animals use to conserve energy during periods of limited resources.
Torpor vs Hibernation
Torpor is a short-term physiological state of reduced metabolic activity that allows animals to conserve energy during unfavourable conditions. Hibernation is a long-term state of dormancy that occurs during winter when food resources are scarce and last for several months.
Torpor is a state of lowered metabolic activity and body temperature assumed by several animals in response to environmental conditions which are adverse in amount, especially heat and cold.
Animals that undergo torpor consist of some mammals (marsupial species), birds (even hummingbirds), bats, and rodent species like mice.
The term hibernation is applied to all winter dormancy kinds of invertebrate animals.
Hibernators consist of several amphibians, reptiles, and fishes that overwinter with a temperature of the body near freezing, as well as a few other mammals like bears spend sleeping in dens in most of the winter.
Comparison Table
| Parameters of Comparison | Torpor | Hibernation |
|---|---|---|
| Interpretation | It is a regulated hypothermia state that allows saving animals’ energy at low temperature’s prolonged period. | It lasts for short periods and sometimes only nights or days (up to the feeding pattern) |
| Foraging | Accompanied by continued foraging | Do not feed during this period |
| Duration | Lasts for short periods and sometimes only nights or days (up to the feeding pattern) | Lasts for several months, weeks, or days (up to the species) |
| State | Involuntary | Voluntary |
| Examples | Big brown bats, the kangaroo mouse, and the California pocket mouse. | Wood frogs, box turtles, and hedgehogs. |
What is Torpor?
Torpor considers having a low body temperature period and metabolism that lasts from days to weeks. During the active part of the day, animals following torpor maintain normal activity levels and body temperature.
But their body temperature and metabolic rate drop during a portion of the day, at night, to conserve energy.
Torpor following animals are not dependent seasonally and can be a vital part of energy conservation at any time of year. The torpor evolution likely accompanied the homeothermy development. Animals above ambient temperature are above to maintain a body temperature when other members of their species fail to have a fitness temperature.
Merits of internal temperature maintenance consist of less susceptibility to extreme temperature drops and increased foraging time. The slowing metabolic rate of energy conservation in periods of insufficient resources is the chiefly noted purpose of torpor.
The conclusion is based mainly on the studies in the laboratory where torpor was observed following food deprivations.
For other torpor’s adaptive function, there is evidence where animals are examined in a natural context, like the observation of fat conservation in small birds.
What is Hibernation?
Hibernation is a state of metabolic depression and minimal activity. It is a seasonal heterothermy characterized by slow heart rate and breathing, low body temperature, and low metabolic rate.
Although, this term is traditionally reserved for deep hibernators like rodents.
This term has been redefined to consist of animals like bears. Now, it is applied based on suppressing active metabolic rather than in body temperature absolute decline.
To save energy, an endothermic animal decreases its body temperature and metabolic rate.
Before entering hibernation, there is a requirement to store enough energy in animals to last through the dormant period duration, possibly as long as the whole winter.
In larger species, they become hyperphagic by eating food in large amounts, and the form of fat deposits stores energy.
On the other hand, in small species of food, caching replaces eating and becomes fat. Ectothermic animals also undergo dormancy and metabolic suppression,, which in several invertebrates is considered diapause.
The term brumate is used by some researchers to describe reptiles’ winter dormancy.
Main Differences Torpor and Hibernation
- When it comes to inactivity, animals of varying sizes can use it. But daily heterotherms are smaller in comparison to hibernators. In contrast, those following hibernation are mainly bigger than daily heterotherms.
- In daily heterotherms, the temporal control of exit/ entry is governed by circadian regulation. On the contrary, from the circadian system, hibernators have uncoupled the control of torpor.
- Torpor’s mean minimum metabolic rate is 35% of the basal metabolite rate in daily heterotherms. On the other hand, during hibernation, the mean minimum metabolic rate is 6% of the basal metabolite rate.
- The state of torpor is triggered by the availability of food and ambient temperature, which indicate the requirement to conserve energy. On the flip side, hormone changes and day length trigger the state of hibernation within the animals.
- Regarding geographical distribution, the daily heterotherms live at lower average latitudes. Meanwhile, the distribution of hibernators are at a higher average compared to daily heterotherms.
References
- https://onlinelibrary.wiley.com/doi/abs/10.1111/brv.12137
- https://www.tandfonline.com/doi/abs/10.1081/CBI-100101036
Last Updated : 01 July, 2023
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Piyush Yadav has spent the past 25 years working as a physicist in the local community. He is a physicist passionate about making science more accessible to our readers. He holds a BSc in Natural Sciences and Post Graduate Diploma in Environmental Science. You can read more about him on his bio page.
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