Torpor

Daily Torpor, sometimes called temporary hibernation is a (usually short-term) state of decreased physiological activity in an animal, usually characterized by a reduced body temperature and rate of metabolism. Animals that go through torpor include birds (even tiny hummingbirds, notably Cypselomorphae) and some mammals such as mice, and bats. During the active part of their day, animals that undergo daily torpor maintain normal body temperature and activity levels, but their temperature drops during a portion of the day (usually night) to conserve energy. Torpor is often used to help animals survive during periods of colder temperatures, as it allows the organism to save the amount of energy that would normally be used to maintain a high body temperature.

Torpor may extend for a longer period of time. Some animals such as groundhogs, ground squirrels and jumping mice enter this intensely deep state of hibernation for the duration of the winter. Lungfish switch to the torpor state if their pool dries out; tenrecs switch to the torpor state if food is scarce during the summer in Madagascar. This prolonged and deep torpor during summer months is known as aestivation. Black bears, although often thought of as hibernators, do not truly enter a state of torpor: while their body temperatures lower along with respiration and heartbeat, they do not decrease as significantly as most animals in a state of torpor, and bears are still responsive. Still, there is much debate about this within the scientific community: some feel that black bears are true hibernators that employ a more advanced form of hibernation.

Bats, especially species in temperate regions suffering harsh winters, rely upon torpor to survive. Lowering the body temperature to the ambient temperature allows them to enter torpor for prolonged periods at a lower metabolic cost. Oxygen consumption, heart rate and breathing rates are all lowered significantly meaning less energy is required to survive. Torpor is important in daily cycles to conserve energy as well as prolonged torpor, or hibernation. Pre-hibernation feeding builds up layers of fat which are used as the energy source during torpor. Arousal from torpor in bats is facultative, not obligate, but comes at a high energy cost, meaning awakening must be for a good reason.

Other uses of the word

Torpor is alternatively used as a reference to any non-physiological state of inactivity. As an example, recently naturalists have learned that female crocodiles enters a deep torpor without aggression during their short egg laying period.

Finally, it is also used to refer to a state of near-death in the role playing games "Vampire: the Masquerade" and "Vampire: the Requiem", which is achieved once a vampire character sustains full lethal damage.

See also

Critical thermal maximum

Dormancy

Estivation

Stupor

Notes

Category:Animal physiology Category:Ethology