Who would have thought that dolphins might be an important part of a war effort? Dolphins have natural abilities that allow them to detect underwater mines, potentially saving many lives and millions of dollars of marine equipment. Take this quiz to learn more about the dolphin's role in disarming mines.
Mines have caused more damage to ships than any other cause.
Since the 1960s, the U.S. Navy has been training and using dolphins to find these underwater explosives.
Dolphins are rewarded with fish when they spot a suspicious, manmade, metal object from far away. This conditions the dolphins so that they know they will be rewarded when they find such an object in the ocean.
Dolphins poke an appropriate signifier with their nose when they have spotted a mine. A signifier might be a ball.
A dolphin is given a special device, known as an acoustic transponder, which it leaves in the area near where the mine was spotted. The transponder produces a distinct sound so that human divers can find the mine later.
Enemies often disguise mines so that they look like natural marine objects, which a mechanical device would not detect as a mine. However, dolphins are able to differentiate between man-made and natural objects, making them useful mine detectors.
Sonar refers to sound navigation and ranging. It is used to detect an object's location under water using sounds.
Water may be too murky to see properly. In addition, sound travels faster underwater than it does in air.
Like sonar, the dolphin creates a sound and sends it out. The sound bounces off objects and returns to the dolphin, who senses it and interprets how far away the object that reflected the sound is.
Dolphins, as well as bats and whales, use echolocation. This is a type of active sonar, as opposed to passive sonar, which is simply listening for noises from other active objects.
Dolphins can differentiate between a BB gun pellet and kernel of corn from 50 feet away, using echolocation.
The returning sounds are absorbed through the dolphins jaw. From the jaw the sound is conducted through a passage of fat to the dolphin's inner ear, where nerve impulses carry the signal to the brain. The brain then interprets the characteristics of the object, including its size, shape and the material it is made from.
When dolphins make different clicking sounds they are adjusting the frequency of the pitch, sometimes reaching frequencies that cannot be heard by humans. They use the different frequencies to help them identify an object.
Nets do not reflect a signal, so dolphins are unaware of them and get caught.
Nets now come with plastic beacons that reflect and amplify echolocation signals, warning the dolphins that there is something there.
The navy explains that mine-hunting is not dangerous for dolphins, since the dolphins are not trained to get close to mines. In fact, the reason that dolphins are used is because they can detect mines from a distance.
Mines are designed not to detonate if disturbed by marine creatures, otherwise they would detonate as soon as they entered the water. Rather, a metallic ship is required to set off a mine, making it safe for dolphins to be near a mine.
This transportation process, which may involve shipping the dolphins in tanks during a long airplane ride, may create stress that could weaken the dolphins' immune systems.
Dolphins are transported to mine-infested waters on slings in tanks. They have to endure this for long airplane rides. The stress of transportation can weaken a dolphin's immune system.
Animal rights activists are concerned that dolphins may be moved to waters that are too cold for them and may get lost in the unfamiliar waters.