Hibernation Research

Much more remains to be learned about hibernation generally, but one aspect of it is likely to prove more than usually elusive. This concerns the precise mechanism by which the hibernation is terminated. A faint clue to this is given in some recent research on another North American ground squirrel.

Not only does the duration of hibernation vary from one species to another, it will vary also in individuals belonging to the same population. This is true more especially for the California ground squirrel. In this a large number of the adult females will hibernate from the beginning of the summer until the following December to January. The males and also the young, both male and female, have a much shorter period of hibernation. For some years past scientists studying the requirements for inter-planetary travel have considered how far it might be possible to induce in astronauts a condition resembling the state of hibernation in animals. The idea would be to put the astronauts to sleep on long journeys into space without using drugs.

This possibility may have been brought a step nearer by some experiments carried out by an American doctor on dogs, cats, mice and rats, animals that do not normally hibernate, to see if he could induce in them a state of hibernation. Each animal was injected with a small amount of a substance taken from the brain of a ground squirrel, with the result that they all fell asleep. This sleep seemed to resemble true hibernation since there was a drop in their body temperature, and their breathing and heart-beats became slower. The animals were subsequently revived by the application of warmth similar to that experienced by a hibernating animal with the arrival of spring. Natural hibernants, such as the dormouse and the hedgehog, that curl up and sleep through the winter, appear to have a mechanism that switches on consciousness again when the warmer weather of spring returns. So far we have little idea what this may be, and if an induced hibernation is to be used it would be necessary to learn the secret of the automatic re-awakening. Then, it might be possible also to use it in the treatment of disease, as well as for space travel. At present, when sleep is necessary in the treatment of a patient, drugs need to be used, but these may have bad side-effects. We may, therefore, in the near future, find the ground squirrel featuring importantly in medical research.

One of the features of the arousal from hibernation is the great strain thrown on the animal's whole system, and on the nervous system in particular. The heart, which beats 3 to 5 times a minute during hibernation is stepped up to around 400 times a minute, and this increase takes only 20 minutes. The intake of oxygen during hibernation is only 20 millilitres, but reaches nearly two hundred times this amount about half-an-hour after arousal. Put in another form, a ground squirrel awakens for a total of about 18 days during a period of six-months' hibernation, but in these few wakeful periods uses nine times the amount of energy used during the rest of the hibernation (about 5 months).