Question 2 of 21

What is the most common cause of ship damage?

... Mines have caused more damage to ships than any other cause.

Question 3 of 21

Since when have dolphins been used to find underwater mines?

... Since the 1960s, the U.S. Navy has been training and using dolphins to find these underwater explosives.

Question 4 of 21

How are the dolphins trained?

... 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.

Question 5 of 21

How do the dolphins indicate to humans that they have spotted a mine?

... Dolphins poke an appropriate signifier with their nose when they have spotted a mine. A signifier might be a ball.

Question 6 of 21

How is the location of the mine marked?

... 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.

Question 7 of 21

Why are dolphins such useful mine detectors?

... 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.

Question 8 of 21

What does sonar refer to?

... Sonar refers to sound navigation and ranging. It is used to detect an object's location under water using sounds.

Question 9 of 21

Why is sound good for detecting things under water?

... Water may be too murky to see properly. In addition, sound travels faster underwater than it does in air.

Question 10 of 21

Dolphins use sonar technology to find objects. How does sonar work?

... 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.

Question 11 of 21

What is the type of sonar used by dolphins called?

... 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.

Question 12 of 21

From how far away can dolphins determine the difference between a BB gun pellet and a corn kernel?

... Dolphins can differentiate between a BB gun pellet and kernel of corn from 50 feet away, using echolocation.

Question 13 of 21

Which part of the dolphin's body absorbs the echo?

... 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.

Question 14 of 21

Why do dolphins make different clicking sounds?

... 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.

Question 15 of 21

Why are dolphins prone to getting caught in nets?

... Nets do not reflect a signal, so dolphins are unaware of them and get caught.

Question 16 of 21

How are dolphins prevented from getting caught in nets?

... Nets now come with plastic beacons that reflect and amplify echolocation signals, warning the dolphins that there is something there.

Question 17 of 21

How does the navy defend its use of dolphins for mine-disarming to animal rights groups?

... 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.

Question 18 of 21

What sort of object can detonate a mine?

... 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.

Question 19 of 21

What is a potential hazard of transporting dolphins to potentially mine-infested waters?

... 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.

Question 20 of 21

What happens to dolphins when they are transported to mine-infested waters?

... 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.

Question 21 of 21

What is a concern for dolphins when transferring them to different waters?

... 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.