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Dolphins, the only mammals to discriminate rhythmic patterns, are being used by the US navy to detect mines. Peter Marren reports
ONE of the strangest stories to emerge from the ruins of Hurricane Katrina is a tale of military-trained dolphins on the loose in the Gulf of Mexico. The animals were reportedly being used by the US navy to detect stray torpedoes and mines and were controlled using signals transmitted to a neck harness. It is possible that some were armed with toxic darts tied to their backs to immobilise terrorists or enemy agents. "If divers or windsurfers are mistaken for a spy or suicide bomber, they could fire," warned an accident investigator close to the US Government’s marine fisheries service. Elsewhere in the dolphin world, a study to be published later this month reveals that they can be trained to respond to music — and even reproduce the simple two-note theme from the 1960s television programme about the Caped Crusader. Dolphins are clever creatures indeed. The Louisiana dolphins were apparently kept in training ponds close to Lake Pontchartrain, whose floodwaters helped to devastate New Orleans. The possibility that they escaped into the ocean surfaced after a separate group of "civilian" dolphins disappeared from a commercial dolphinarium on the Mississippi coast during the hurricane. Eight of them were later recovered alive with the help of the navy. However, the dolphins were not returned to their owners until the authorities had had a close look at them, sparking fears that some military dolphins had also escaped during the hurricane. The US navy has refused to comment. Dolphins have been used by both the American and Russian armed forces since the 1950s. The US navy had originally hoped to observe the dolphin’s locomotive and sensory systems in an attempt to improve the design of undersea weapons. They also carried out a range of classified experiments to study the uncanny ability of dolphins to locate and retrieve objects from the seabed. It soon became apparent that dolphins were very much better at this task than human divers. It was also clear that they were intelligent animals that were capable of learning tasks quickly. To teach a dolphin some new tricks, scientists had to find a way of communicating with them. Unlike humans, dolphins have two forms of speech. One is a medley of whistles that they use to communicate with one another; the second a series of acoustic clicks used to locate food. The clicks are used to locate prey in murky water by bouncing high-frequency sound off them. By emitting a stream of repeated clicks, the dolphin can also gauge the object’s direction and speed. Dolphins studied in Cardigan Bay off the coast of Wales could detect and then catch large fish from up to 72 m away. A dolphin’s mind is like a ship’s sonar, gathering sufficient information about the size and speed of an enemy object to shoot it down with lethal accuracy. Their ability to detect and then monitor an object is thought to take place at an unconscious level. Scientists learned how to communicate with dolphins using an instrument called a hydrophone, an underwater sound projector which can deliver high-pitched sounds audible to the animals. They learned that dolphins can be trained to recognise commands. They also found that the dolphins were able to mimic sounds and rhythms relayed through the hydrophone. Studies soon to be presented at a meeting of the Acoustical Society of America will reveal that dolphins can even be trained to respond to music. One has learned to whistle the two-note theme from Batman, one short, the other long: "Bat-maaaan". Appropriately, perhaps, it learned to produce the tune when presented with a Batman doll, for which it received the usual reward for cetacean intelligence — a fish. The singing dolphin has broken one of the barriers that seemed to have set humans apart from the rest of the animal kingdom. Gordon Bauer, associate professor at the New College of Florida, says: "This is the first report of a non-human mammal being able to discriminate rhythmic patterns." With intelligence added to unusual physical gifts, it was only a matter of time before captive dolphins were drafted into the wholly human preoccupation with security and warfare. From the 1960s, the US navy is known to have employed up to 240 dolphins, as well as beluga whales, killer whales and sea-lions. The work was conducted in secrecy but details emerged in 1988 when trainers who worked with navy dolphins went public. More sinister was the use of dolphins in a "swimmer nullification program", where a long hypodermic needle was fastened to a dolphin’s beak for firing a bullet of carbonic acid into an enemy frogman. With both the Russians and Americans using dolphins there was, for a while, the science-fiction prospect of "dolphin wars", in which one lot carried electronic counter-measures to jam the sonar of the other. Fortunately with the ending of the Cold War, the prospect of rival dolphins attacking one another has receded. — By arrangement with The Independent |
