Difference Between Torpor and Hibernation

When it comes to animals and plants, to protect themselves from the environment’s harmful effects they use distinctive mechanisms in nature. Mainly during periods of drought, cold weather, or depletion of the available food resources. Several bird and mammal species temporarily abandon euthermia as well as drastically reduce energy expenditure and body temperature.  

Through this, they can survive during periods with environmental conditions that are unfavorable. 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. 

Torpor vs Hibernation 

The main difference between torpor and hibernation is their geographical distribution. Those who follow torpor usually live at lower average latitudes. On the other hand, the distribution of hibernators is at higher average latitudes in comparison to daily heterotherms. 

Torpor and Hibernation

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 rodents species like mice

The term hibernation is generally applied to all winter dormancy kinds 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 Between Torpor and Hibernation 

Parameters of ComparisonTorporHibernation
InterpretationIt is a condition of hypometabolic especially in eutherms which enables animals to survive unfavorable condition’s periods.It is a regulated hypothermia state which allows saving energy of animals at low temperature’s prolonged period.
ForagingAccompanied by continued foragingDo not feed during this period
DurationLasts 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 InvoluntaryVoluntary
ExamplesBig 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 as well as metabolic rate drop during a portion of the day generally at night to conserve energy.  

Torpor following animals are not dependent seasonally and can be a vital part of at any time of year for energy conservation. The torpor evolution likely accompanied the homeothermy development. Animals above ambient temperature are above to maintain a body temperature when other members of its species fail to have a fitness temperature.  

Merits of internal temperature maintenance consist of less susceptibility to temperature extreme 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 largely based on the studies in the laboratory where torpor was observed for 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 that is 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 suppression of active metabolic rather than in body temperature any absolute decline. To achieve the saving of energy, an endothermic animal generally decreases its body temperature and its 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 period which in several invertebrates is considered as diapause. The term brumate is used by some researchers to describe reptiles’ winter dormancy. 

Main Differences Torpor and Hibernation 

  1. When it comes to torpor, animals of varying sizes can use it. But daily heterotherms are generally smaller in comparison to hibernators. In contrast, those who follow hibernation are mainly bigger compared to daily heterotherms.  
  2. In daily heterotherms, the temporal control of exit/ entry into is governed by the regulation of circadian. On contrary, from the circadian system, hibernators have uncoupled the control of torpor.  
  3. In torpor, the 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.  
  4. The state of torpor is generally triggered by the availability of food and ambient temperature which indicate the requirement to conserve energy. On the flip side, by hormone changes and daylength, the state of hibernation is triggered within the animals.
  5. In terms of geographical distribution, the daily heterotherms usually live at lower average latitudes. Meanwhile, the distribution of hibernators are at higher average in comparison to daily heterotherms. 

Conclusion 

It can be concluded that hibernation is one of the subtypes of torpor. During the torpors period, animals are accompanied by continued foraging. In contrast, hibernators do not feed during the hibernation period. Duration of torpor lasts for short periods and sometimes only nights or days which is up to the feeding pattern. On the other hand, hibernation generally lasts for several months, weeks, or days which is up to the species.  

Torpor is a condition of hypometabolic linked with low body temperature especially in eutherms which enables animals to survive unfavorable condition’s periods. Meanwhile, hibernation is a regulated hypothermia state which allows saving energy of animals at low temperature’s prolonged period. Examples of torpor are the kangaroo mouse, big brown bats, and California pocket mouse. On contrary, box turtles, wood frogs, and hedgehogs are examples of hibernation.

References  

  1. https://onlinelibrary.wiley.com/doi/abs/10.1111/brv.12137
  2. https://www.tandfonline.com/doi/abs/10.1081/CBI-100101036
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