In 1832, Alexander Wilson first described hummingbird 'torpor' in his book, American Ornithology.

He wrote, "No motion of the lungs could be perceived ... the eyes were shut, and, when touched by the finger, [the bird] gave no signs of life or motion."

Hummingbirds can enter a state of overnight hibernation or torpor and drop their oxygen consumption from 0.67 to 0.003 ml O2/min/g body wt (a 99.5% fall), lower their heart rate from 1200 to 48 beats/min (a 96% fall) and lower their body temperature from 41 to 15oC. During torpor the body's furnace and thermostat are switched down to "pilot light" so that the animal burns much less energy and helps keep its metabolic supply-demand ratio in balance. As the day warms, the bird slowly reanimates and their basal metabolism speeds up by over 200-times and it resumes life in the fast lane.

At the other end of the temperature scale, there are a variety of desert frogs and toads that display a different set of survival strategies. During drought, the water-holding frog (Cyclorana platycephalus) stores water in its huge bladder, burrows down 1 to 3 meters into soft soil, forms a cocoon and 'sleeps' for months to years without water. The frog's metabolic rate typically falls by 70-80%, its breathing becomes episodic and heart rate slows to a few beats per minute. After it rains, the frog eats its cocoon and emerges from its subterranean home to drink, breed and eat, and when the free water dries up, the animal burrows down and prepares for another estivating period below the hot and dry desert surface.

What lessons can be learned from natural hibernators and applied to achieve greater protection of the heart, brain and other organs during clinical interventions and surgery? Can new therapeutics or procedures be designed to make current practices safer for the patient and more predictable for the surgeon?