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A period of dormancy in winter by some animals known as - Hibernation.
nding on the species, it's size, environmental trigger (e.g., ambient temperature, light levels, etc.), time of year, body condition, and fat stores, hibernation could arguably last as short as a day or less, or many months. Indeed, for some animals that spend the greater part of the year in hibernation, it is the default-mode of existence. The longest reported hibernation bout on record in a mammal, a marsupial, is just over a year (ref). Additional difficulty in defining hibernation comes by way of the fact that small mammals frequently arouse during hibernation. Unequivocally, however, torpid states, whatever the metabolic energy threat, are fundamentally typified by lowered core-body temperatures, prolonged pauses between breaths and lowered heart rates, i.e., to values below those of BMR. Even here though, it remains unclear what degree of suppression is required. The fact that the scope for metabolic rate reduction scales with body mass, means that large animals, because of an already lowered size-related basal metabolic rate require less scope for reaching the universal minimum metabolic rate (UMMR), a rate found to be invariant in animals varying in size from bacteria to blue whales. In other words, only a ca. 75% decrease in metabolic rate below BMR is required to reach the UMMR in animals the size of, say, bears or even a seal, compared to say a small rodent, the latter of which can lower metabolic rate to single digit percentages of BMR. This is also why small animals are able to cool, track and tolerate ambient temperature better than larger animals, and also why bears were not considered true hibernators by many for such a long time. It is becoming evident, however, that the torpor can be triggered by many metabolic energy threats and comes in many shades, form a continuum that utilize similar underlying mechanisms.Hibernation during the summer months is known as aestivation. Some reptile species (ectotherms) are said to brumate, or undergo brumation, but any possible similarities between brumation and hibernation are not firmly established.
A period of dormancy in winter by some animals known as - Hibernation.
Hibernation is a suppressed metabolic state that falls under the umbrella-term of torpor or dormancy, which covers all forms of metabolic suppression. Hibernation, like other forms of torpor, is a widespread and common survival strategy expressed under the threat of a metabolic energy crisis. As the name suggests, however, it has a seasonal connotation suggestive of triggering by lowered ambient temperatures and darkness, e.g., autumn and winter.
Attempts at defining hibernation have proved elusive. For example, merely exposing animals that hibernate does not always trigger hibernation. Instead it may trigger a hypothermia, which is a life-threatening pathologic condition. In addition, the duration for which an animal must remain in torpor to be qualified as a hibernator remains debatable. Depe
nding on the species, it's size, environmental trigger (e.g., ambient temperature, light levels, etc.), time of year, body condition, and fat stores, hibernation could arguably last as short as a day or less, or many months. Indeed, for some animals that spend the greater part of the year in hibernation, it is the default-mode of existence. The longest reported hibernation bout on record in a mammal, a marsupial, is just over a year (ref). Additional difficulty in defining hibernation comes by way of the fact that small mammals frequently arouse during hibernation. Unequivocally, however, torpid states, whatever the metabolic energy threat, are fundamentally typified by lowered core-body temperatures, prolonged pauses between breaths and lowered heart rates, i.e., to values below those of BMR. Even here though, it remains unclear what degree of suppression is required. The fact that the scope for metabolic rate reduction scales with body mass, means that large animals, because of an already lowered size-related basal metabolic rate require less scope for reaching the universal minimum metabolic rate (UMMR), a rate found to be invariant in animals varying in size from bacteria to blue whales. In other words, only a ca. 75% decrease in metabolic rate below BMR is required to reach the UMMR in animals the size of, say, bears or even a seal, compared to say a small rodent, the latter of which can lower metabolic rate to single digit percentages of BMR. This is also why small animals are able to cool, track and tolerate ambient temperature better than larger animals, and also why bears were not considered true hibernators by many for such a long time. It is becoming evident, however, that the torpor can be triggered by many metabolic energy threats and comes in many shades, form a continuum that utilize similar underlying mechanisms.Hibernation during the summer months is known as aestivation. Some reptile species (ectotherms) are said to brumate, or undergo brumation, but any possible similarities between brumation and hibernation are not firmly established.
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