|
Hibernating bats hanging from
the ceiling of caves and the rafter of an old building (click on top left
and bottom right images for name of species). |
Hibernation
can be divided into three phases: entrance, deep hibernation, and arousal.
Because they hibernate in places that do not offer great protection
from external disturbances or wide fluctuations in temperature—caves,
mines, wells, cellars, and the hollows of trees—bats often emerge from
deep hibernation only to go through the three phases again. Over the course
of a single cold season, this cycle can repeat every few days to many
weeks, though one arousal every 20 days serves as a rough mean for all
species (Altringham, 1996).
Fortunately,
bats are able to enter torpor and arouse more easily than other hibernators
of its size (Jansky, 1961) allowing them
to respond to various stresses. For example, if ambient temperatures
begin to drop, a hibernating bat will often arouse and fly to a more stable
shelter (Hill, 1984)—the temperature needed
to invoke the arousal depends on the species. Other responses to temperatures
dropping to 0ºC or below include metabolic
compensation, supercooling or death (Davis,
1967). |
Arousal
Stimuli I
