Animals at the extremes: Hibernation and torpor
Animals at the extremes: Hibernation and torpor

This free course is available to start right now. Review the full course description and key learning outcomes and create an account and enrol if you want a free statement of participation.

Free course

Animals at the extremes: Hibernation and torpor

5.7 Summary

BMR is regulated independently of T b at least in hibernating mammals. Entry into hibernation is characterized by a gradual fall in RQ, which indicates a switch from carbohydrate to lipid metabolism for energy provision (through the phosphorylation of pyruvate dehydrogenase, the inhibitor of mitochondrial fatty acid uptake). There is evidence that some other vertebrates, such as hibernating frogs, may continue to use carbohydrate catabolism or activate gluconeogenic pathways when arousal episodes completely deplete stored triacylglycerols.

The most important adaptive modifications of the mitochondrion are reduced oxidative metabolism, the reversal of the proton leak across the inner membrane as an energy-saving mechanism during hibernation, and an increase in production of uncoupling proteins (UCP) in preparation for metabolic thermogenesis during arousal episodes.

Lung ventilation is linked to oxygen supply in euthermic animals, but in hibernation where tissue blood flow is almost absent it becomes less important. The characteristic inspiratory patterns of hibernation, as well as the fall in heart rate, have been shown to follow passively from the depression ofT b.

The energy budget of mammals for euthermia, torpor and arousal can be estimated both in the laboratory and natural habitats. For small mammals that are obligate hibernators, energy saving is in excess of 80% for the winter months and about 60% averaged over the year. Lactation and gestation can stretch the energy budget of female mammals considerably, and they may display further adaptations to minimize the cost. Hibernation should not, however, be seen as the universal solution for energy saving in winter and considerations of size, behaviour pattern and habitat all have an effect upon the useful duration of torpor bouts or whether torpor is an appropriate strategy at all. Hibernation physiology may be a major factor in determining the biogeographical and ecological diversity of mammals and perhaps other vertebrates.


Take your learning further

Making the decision to study can be a big step, which is why you'll want a trusted University. The Open University has 50 years’ experience delivering flexible learning and 170,000 students are studying with us right now. Take a look at all Open University courses.

If you are new to university level study, find out more about the types of qualifications we offer, including our entry level Access courses and Certificates.

Not ready for University study then browse over 900 free courses on OpenLearn and sign up to our newsletter to hear about new free courses as they are released.

Every year, thousands of students decide to study with The Open University. With over 120 qualifications, we’ve got the right course for you.

Request an Open University prospectus