Elephants

In the Middle Ages people believed that an elephant could not lie down to sleep because once it was on its side it was unable to get up again. This was because, so the notion ran, it had no joints in its legs. Another popular idea, also, at that time was that in order to sleep an elephant leaned against a tree, and therefore anyone who wanted to capture an elephant had only to go out at night, chop down the tree against which the elephant was leaning, and make an easy capture.

It is of interest to see that during this same period there was another current idea. This was that in Africa elephants were hunted in another way. Two maidens, so the story ran, would go out into the desert, one carrying an earthenware vessel, the other carrying a sword. When they reached elephant country they would begin to sing. The elephant had such a liking for their song that he would fall asleep under the charm of it, so that one maiden could then pierce his side with the sword and the other could catch the blood in the earthenware vessel. The blood was supposed to be used for dying cloth, but nobody seems to have explained why anyone should go into a desert to catch elephants. Until a very few years ago there was little more information on how and when elephants sleep than is contained in these absurd stories. Such information as we had suggested that they spent much of the night dozing and that they fell into a deep sleep, even snoring loudly, for about three hours and that for this they lay on their sides.

Elephants by nature are suspicious and have a lively sense of curiosity. When first placed in new surroundings they are very much alive to the smallest sounds and movements. To carry out experiments at night, to see when and how they sleep, proved difficult, which is the main reason why we have so long been in doubt, so a method had to be found, by which the experimenter could keep watch on them from a distance.

An infra-red device was set up and this in turn threw a picture on a television screen in an office some few hundred yards away. The elephants did not seem in the least affected by the presence of infra-red lamps although their eyes reflected the light particularly strongly. Three elephants, two bulls and a cow, were chosen for the experiment. It being their first night in a new den they were all restless and inquisitive and spent many hours roaming about and inspecting their new quarters. Not until 3.00 a.m. did the leader of the group, a female, decide it was bedtime. Having examined every corner of the den she trundled the two young bulls into the safest corner, and then put herself on guard.

Soon the two young elephants with heads to the wall were showing signs of deep sleep, by rolling up their trunks, leaning against each other and swaying from side to side. This regular swaying motion is no doubt used for relieving the weight on first the legs on one side and then the legs on the other side. For more than three hours the female remained on watch, sometimes scenting the air outside with her trunk, and sometimes "fingering" the sleeping youngsters, also with her trunk. Clearly, she was wide-awake listening for any sound.

Finally, not long before dawn, the leader took up her position next to the others but facing the opposite direction (or the point at which danger would first approach) and she too soon fell into a light sleep although she was ready to respond to danger at any moment. These first observations were added to, later, and now we can say that both Indian and African elephants use two different positions for sleeping, one standing and one lying on the side. To lie down an elephant uses similar movements to those of a horse except that it will sometimes do what no horse ever does: it will make a straw pillow on which to rest its head.

While standing asleep an elephant breathes at about half the rate it does during waking hours, and its breathing is even slower when it is sleeping lying down. On one occasion 17 elephants were kept under observation. They usually slept for two periods of approximately equal length, during each night. These two periods totalled about 5 hours in all of which 20 minutes were slept standing and the rest lying down. When elephants are in groups, such as these were, they usually all sleep at the same time. No doubt this is due, as in ourselves, to one setting an example and the rest following suit.