Torpor

Dedicated to all Zoologist

1. Presentation Topic: Torpor By Shams Ullah Reg. No. : ZO220172051 Submitted to : Ms . Naila Gul (Lecturer) Department of Zoology ,KUST,Kohat

2. What is torpor??? Torpor  is a state of decreased physiological activity in an animal, usually by a reduced  body temperature  and  metabolic rate . Torpor enables animals to survive periods of reduced food availability. The term "torpor" can refer to the time a  hibernator  spends at low body temperature, lasting days to weeks, or it can refer to a period of low body temperature and metabolism lasting less than 24 hours, as in "daily torpor".

3. Animals that undergo daily torpor include birds (even tiny hummingbirds, notably Cypselomorphae ) and some mammals, including many marsupial species, rodent species (such as mice), and bats. During the active part of their day, such animals maintain normal body temperature and activity levels, but their metabolic rate and body 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 them to save the energy that would normally be used to maintain a high body temperature.

4. Some animals seasonally go into long periods of inactivity, with reduced body temperature and metabolism, made up of multiple bouts of torpor. This is known as hibernation if it occurs during winter or aestivation if it occurs during the summer. Daily torpor, on the other hand, is not seasonally dependent and can be an important part of energy conservation at any time of year.

5. Torpor is a well-controlled thermoregulatory process and not, as previously thought, the result of switching off thermoregulation. Marsupial torpor differs from non-marsupial mammalian (eutherian) torpor in the characteristics of arousal. Eutherian arousal relies on a heat-producing brown adipose tissue as a mechanism to accelerate rewarming. The mechanism of marsupial arousal is unknown, but appears not to rely on brown adipose tissue.

6. Evolution The evolution of torpor likely accompanied the development of  homeothermy . Animals capable of maintaining a body temperature above ambient temperature when other members of its species could not would have a fitness advantage. Benefits of maintaining internal temperatures include increased foraging time and less susceptibility to extreme drops in temperature. This adaptation of increasing body temperature to forage has been observed in small nocturnal mammals when they first wake up in the evening

7. Although homeothermy lends advantages such as increased activity levels, small mammals and birds maintaining an internal body temperature spend up to 100 times more energy in low ambient temperatures compared to ectotherms. To cope with this challenge, these animals maintain a much lower body temperature, staying just over ambient temperature rather than at normal operating temperature. This reduction in body temperature and metabolic rate allows the prolonged survival of animals capable of entering torpid states.

8. Function I n times of insufficient resources is the primarily noted purpose of torpor. This conclusion is largely based on laboratory studies where torpor was observed to follow food deprivation. There is evidence for other adaptive functions of torpor where animals are observed in natural context of small migrant birds to increase their body fat. Hummingbirds, resting at night during migration, were observed to enter torpor which helped conserve fat stores for the rest of their migration.

9. Fat conservation in small birds This strategy of using torpor to increase body fat has also been observed in wintering chickadees. Black-capped chickadees, living in temperate forests of North America, do not migrate south during winter. The chickadee can maintain a body temperature 12 °C lower than normal. This reduction in metabolism allows it to conserve 30% of fat stores amassed from the previous day. Without using torpor the chickadee would not be able to conserve its fat stores to survive winter.

10. Advantage in environments with unpredictable food sources Torpor can be a strategy of animals with unpredictable food supplies.  For example, high-latitude living rodents use torpor seasonally when not reproducing. These rodents use torpor as means to survive winter and live to reproduce in the next reproduction cycle when food sources are plentiful, separating periods of torpor from the reproduction period. Some animals use torpor during their reproductive cycle, as seen in unpredictable habitats. They experience the cost of a prolonged reproduction period but the payoff is survival to be able to reproduce at all. The  eastern long-eared bat  uses torpor during winter and is able to arouse and forage during warm periods.

11. Parasite resistance by bats A drop in temperature from torpor has been shown to reduce the ability of parasites to reproduce. Ectoparasites of bats in temperate zones have reduced reproductive rates when bats enter torpor. Where bats do not enter torpor the parasites reproduce at a constant rate throughout the year.