Bluetongue1
Well-Known Member
Sorry about the delay. Given this is a single post, I added a few bits and pieces.
The term hibernation was originally used to describe any animal that entered an extended period of winter dormancy. (It has also been applied to plants.) This seasonal state of inactivity is characterized by low body-temperature, slowed breathing and heart-rate and low metabolic rate. Bear in mind that reptiles are ectotherms i.e. they derive most of their body heat from the environment, and therefore their body temperature is subject to changes in their environment; mammals and birds are endotherms i.e. they derive most of their body heat by generating it inside their bodies, and therefore can maintain a relatively constant body temperature independent of environmental temperatures.
The term ‘brumation’ was first introduced in 1965 to distinguish between winter dormancy in reptiles and that in mammals. Part of the reason is that there were some clearly observable differences. Hibernating mammals would not emerge at all for the duration of hibernation. Whereas reptiles were known to emerge on warmer, sunny days to bask and to drink. However the key difference identified was that endotherms have to actively alter their internal metabolism to achieve the drop in body temperature, and the other changes that occur. In contrast, reptiles, being ectotherms, are simply responding to changes in their external environment.
So hibernation is defined as something that occurs in endotherms; and brumation is something that occurs in ectotherms.
The term hibernation was traditionally used for animals entering a "deep sleep". It was discovered that bears only drop their body temperature about 5 or 6 degrees Celsius and yet their metabolic rate drops about 75%. They also have periods where their metabolic rate returns to near normal for several days at a time. This is why the current definition of hibernation is based on active metabolic suppression and no longer the degree of decline in body temperature.
A further complication is daily and multiple day torpor. Many, if not most small mammals, including over 40% of Australia’s native mammals, are capable of entering a torpid state to conserve energy reserves. Small mammals in cold weather will do so on a daily basis, going into torpor at night. Humming birds do the same thing due their extremely high metabolic rate when active. This can also occur in response to a lack of available food. A lot are capable of extending the torpor period over a period of several days when need be. Many experts believe that the processes of daily and short term torpor, and hibernation, form a continuum and utilize similar mechanisms. For the moment, torpor is used for short term dormancy and hibernation for a significantly extend period of dormancy.
The term hibernation was originally used to describe any animal that entered an extended period of winter dormancy. (It has also been applied to plants.) This seasonal state of inactivity is characterized by low body-temperature, slowed breathing and heart-rate and low metabolic rate. Bear in mind that reptiles are ectotherms i.e. they derive most of their body heat from the environment, and therefore their body temperature is subject to changes in their environment; mammals and birds are endotherms i.e. they derive most of their body heat by generating it inside their bodies, and therefore can maintain a relatively constant body temperature independent of environmental temperatures.
The term ‘brumation’ was first introduced in 1965 to distinguish between winter dormancy in reptiles and that in mammals. Part of the reason is that there were some clearly observable differences. Hibernating mammals would not emerge at all for the duration of hibernation. Whereas reptiles were known to emerge on warmer, sunny days to bask and to drink. However the key difference identified was that endotherms have to actively alter their internal metabolism to achieve the drop in body temperature, and the other changes that occur. In contrast, reptiles, being ectotherms, are simply responding to changes in their external environment.
So hibernation is defined as something that occurs in endotherms; and brumation is something that occurs in ectotherms.
The term hibernation was traditionally used for animals entering a "deep sleep". It was discovered that bears only drop their body temperature about 5 or 6 degrees Celsius and yet their metabolic rate drops about 75%. They also have periods where their metabolic rate returns to near normal for several days at a time. This is why the current definition of hibernation is based on active metabolic suppression and no longer the degree of decline in body temperature.
A further complication is daily and multiple day torpor. Many, if not most small mammals, including over 40% of Australia’s native mammals, are capable of entering a torpid state to conserve energy reserves. Small mammals in cold weather will do so on a daily basis, going into torpor at night. Humming birds do the same thing due their extremely high metabolic rate when active. This can also occur in response to a lack of available food. A lot are capable of extending the torpor period over a period of several days when need be. Many experts believe that the processes of daily and short term torpor, and hibernation, form a continuum and utilize similar mechanisms. For the moment, torpor is used for short term dormancy and hibernation for a significantly extend period of dormancy.