Torpor and Hibernation in Endotherms
avoidance adaptation which animal use is hibernation this
is a state of inactivity and metabolic depression. Of which there are two
groups the Obligate hibernator’s (animals which spontaneously hibernate
annually regardless of ambient temperature or food availability) examples
ground squirrel, rodents, European Hedgehog (,Erinaceus europaeus)
insectivores, monotremes (mammals who lay eggs), marsupials (pouched animals)
and the small tortoiseshell butterfly (Aglais
urticae). And the Facultative hibernators (hibernation occurs due to cold,
stress, food deprivation or both) examples of some of the species are prairie
dog (Cynomys), bears, the white (Cynomys leucurus) and black (Cynomys
ludovicianus) tailed prairie dogs.
In the endothermic species, it is a season or time period which is called heterothermy (animals who have the ability to switch between ectothermic (or poikilothermic) and endothermic (or homoeothermic) strategies).
These changes can are generally used to dissociate the fluctuating metabolic rates of the animals, it occurs in mammals such as the bear species bats, hummingbirds, and many ectothermic animals. (Mayer, 2014)
The fat tailed lemur (Cheirogaleus medius) of Madagascar will hibernate in a tree hole for up to 7 months of the year, as the temperature during the winter months in Madagascar can reach over 300C (860F), the Lemur is dependent on the thermal behaviour of the tree hole, if the tree is poorly insulated the temperature of the lemurs body will fluctuate wildly following the ambient temperature, but if it is well insulated the lemur will undergo normal spells of arousal. Additionally this is the only tropical mammal known to do this (Blanco, et al., 2013)
The hibernation of an animal involves firstly storing up enough energy to last them through the period of hibernation (entire winter). The larger species will become Hyperphagic and consume large amounts of food storing as energy in fat deposits, in the smaller species they will replace becoming fat with food caching. Then as the environmental temperature drops, their body temperature becomes lowered slowing their breathing down, heart rate, and oxygen consumption, the now achieved low metabolic rate, is mediated by a pert of the animal nervous system.
True hibernation requires internal organs like the digestive tract and endocrine system to almost shut down this places a great strain on the animals tissues as they are all directed toward maintaining the metabolism at its most basic (just sustaining life) even the bones and teeth will deteriorate during the hibernation period, hibernators do not stay in this state constantly for the time it hibernates(in most animals it is the coldest times from the beginning of winter to the spring) the arousal periods are more frequent during the beginning and the end of the hibernation period than in the middle. (Mayer, 2014)
Animals who hibernate can be place in to four separate groups depending on how they begin the hibernation period: (Mayer, 2014)
The temperature of the bear: the normal temperature of the bear is 38 0C (1000F) drops during the winter sleep to about 340C (930F) its temperature will seldom drop below 310C (88.20F). (Mayer, 2014) (Hellgren, 1998)
Other mammals who winter sleep (enter torpor) as opposed to hibernate, the chipmunk (Eutamias), the raccoons (Procyon lotor )and bear, the winter sleep instead of hibernation will save the animal the high energy cost and stress of the true hibernation, this additionally means the animal can conserve food, while still having the ability to avoid predation. (Mayer, 2014) (Humphries, et al., 2003)
In the endothermic species, it is a season or time period which is called heterothermy (animals who have the ability to switch between ectothermic (or poikilothermic) and endothermic (or homoeothermic) strategies).
These changes can are generally used to dissociate the fluctuating metabolic rates of the animals, it occurs in mammals such as the bear species bats, hummingbirds, and many ectothermic animals. (Mayer, 2014)
The fat tailed lemur (Cheirogaleus medius) of Madagascar will hibernate in a tree hole for up to 7 months of the year, as the temperature during the winter months in Madagascar can reach over 300C (860F), the Lemur is dependent on the thermal behaviour of the tree hole, if the tree is poorly insulated the temperature of the lemurs body will fluctuate wildly following the ambient temperature, but if it is well insulated the lemur will undergo normal spells of arousal. Additionally this is the only tropical mammal known to do this (Blanco, et al., 2013)
The hibernation of an animal involves firstly storing up enough energy to last them through the period of hibernation (entire winter). The larger species will become Hyperphagic and consume large amounts of food storing as energy in fat deposits, in the smaller species they will replace becoming fat with food caching. Then as the environmental temperature drops, their body temperature becomes lowered slowing their breathing down, heart rate, and oxygen consumption, the now achieved low metabolic rate, is mediated by a pert of the animal nervous system.
True hibernation requires internal organs like the digestive tract and endocrine system to almost shut down this places a great strain on the animals tissues as they are all directed toward maintaining the metabolism at its most basic (just sustaining life) even the bones and teeth will deteriorate during the hibernation period, hibernators do not stay in this state constantly for the time it hibernates(in most animals it is the coldest times from the beginning of winter to the spring) the arousal periods are more frequent during the beginning and the end of the hibernation period than in the middle. (Mayer, 2014)
Animals who hibernate can be place in to four separate groups depending on how they begin the hibernation period: (Mayer, 2014)
- The animal will wait a period of time during
the start of the cold temperatures (1-3 months) and then enters hibernation in
one major temperature reduction, accomplished only when biochemical and
physiological preparations have been enough to prompt the hibernation stimulus,
causing the abandonment of the temperature differential between the ambient (environment)
and body temperature. An example of this is the golden hamster (Mesocricetus
auratus) (Mayer, 2014)
- This group will prepare for hibernation only
waiting a few days in to the cold weather before becoming torpid in one major
temperature decline, the Rock pocket mouse (Chaetodipus intermedius) is a
member of the group of animals who exhibit this form of hibernation. (Mayer, 2014)
- A group that most of the mammalian hibernator’s
belong to, they will wait only a matter of days before they go through a series
of steps where they enter torpid and arousal, each one at successively lower
body temperature, until the level dictated by the stage or preparation for
hibernation is reached, in this group there are the California ground squirrel (Otospermophilus
beecheyi) and the marmots (Marmota). (Mayer, 2014)
- In this group the animals become inactive in
the poikilothermous manner (temperature follows the ambient temperature) bats
are an example of this group. (Mayer, 2014)
The temperature of the bear: the normal temperature of the bear is 38 0C (1000F) drops during the winter sleep to about 340C (930F) its temperature will seldom drop below 310C (88.20F). (Mayer, 2014) (Hellgren, 1998)
Other mammals who winter sleep (enter torpor) as opposed to hibernate, the chipmunk (Eutamias), the raccoons (Procyon lotor )and bear, the winter sleep instead of hibernation will save the animal the high energy cost and stress of the true hibernation, this additionally means the animal can conserve food, while still having the ability to avoid predation. (Mayer, 2014) (Humphries, et al., 2003)