Whales and Dolphins

Even experienced seafarers get little more than occasional glimpses of whales, porpoises and dolphins, other than when they are lying at the surface or leaping from the water or swimming by in schools. Whalers, who come more into contact with them, are too busy chasing them to learn the secrets of their way of life. Consequently, it was not until the first oceanarium was built, in Florida, a quarter of a century ago, that some of the more intimate secrets of their way of life were laid bare. The huge concrete tanks of the oceanarium, filled with sea-water, made possible the keeping of large marine animals in captivity under semi-natural conditions. Yet although much has been learned about porpoises and dolphins, as well as some of the smaller whales, we still know very little about how and when these animals sleep.

The first species to be treated in this way was the bottlenose dolphin. Once in captivity this dolphin had to be fed, and this was done during the day. At night the dolphin slept for long periods, but there was still some doubt whether this might not be the result of being in captivity. After all, if you feed an animal by day it is likely to keep going by day whereas there was always the possibility that bottlenose dolphins might, in the wild state, gear their movements to those of the fish on which they feed. So the question whether bottlenose dolphins sleep more by night than by day when at sea is still not settled. The doubt was increased when some pilot whales were kept in the same oceanarium. When they were first placed in the tanks they spent almost the whole day floating near the surface with their eyes closed and only the blowhole and a part of the back above the surface. The best way to tell whether a whale is asleep is by the rate at which it blows. When a whale is asleep it blows (i.e. breathes) at about half the rate it does when swimming. At first the pilot whales were fed at night, because that was when they were most active, but after a while they started gradually to become more active by day. Then the bottlenose dolphins in the tank started to molest them and they went back to their habit of sleeping at night.

If we look at this another way it seems reasonable to suppose that pilot whales are mainly nocturnal because they feed on squid, and these are more active by night than by day. All the same the pilot whale is the caa'ing or blackfish which for centuries has been hunted by the people of the Faroes, Orkneys and Shetlands, and still is hunted in the Faroes. There the inhabitants drive the schools of pilot whales ashore and slaughter them - and they do this during the day. This could mean that the pilot whale sleeps mainly by day, except on migration. However, a pilot Whale kept in the oceanarium, that was later built in California, slept both by day and by night. It would doze either lying horizontally with its blowhole at the surface, or hanging vertically near the surface, when it was compelled periodically to raise its head to the surface to blow, apparently doing this automatically and without waking.

It could be that even the little we now know on this subject may explain another sea mystery. There are a number of small whales known only from skeletons found on beaches. Each of these species is known from no more than two or three, at most half-a-dozen skeletons. The whales themselves have never been seen alive. This could be because they sleep by day and, like the pilot whale, expose just the blowhole at the surface and no more. About the only other information we have is that the sperm whale seems to be the deepest sleeper of all. It can stay for hours on end near the surface, apparently very fast asleep, and several sperm whales have been killed by ships in head-on collisions. The Greenland right whale also seems to be a heavy sleeper. One did not wake until the bow-waves from a passing ship lapped against it.