Echolocation

Professor Rob Young gives lectures on A days at the back of the ship pertaining to specific marine topics that are applicable to the areas we pass through. His lecture on Sunday revolved around echolocation.

Q: Who has echolocation?
A: Bats, dolphins, and tooth whales

Echolocation is the use of sounds to bounce off of objects a distance away to see how far and big
the object(s) are, as well as if the object(s) are moving or not. This allows the animal to pick up things that they may not pick up with just vision alone. It is basically seeing with sound. The sounds paint images in the animals heads that allows them to visualize the scenario. In fact, there is a species of dolphin in India, which resides in the Ganges and Indus Rivers, that is practically blind because of the water quality. This dolphin relies solely on echolocation to see and maneuver through the river.

When dolphins send out their sounds, it comes from what is called their "melon." the Melon is the part of their head above their eyes. This section is just a fatty section of their bodies, because their skull is actually quite far below this. Thus, on top of the skull remains a body cavity that resembles a melon. This melon section sends out the noises to use for echolocation. The really good echos are produced by short sounds; these paint the best pictures for vision. The animal will not send another echo until the first one returns, otherwise they will get confused between the two.

When the animal gets closer to an object, the echos will be sent out faster (even as fast as 100 echos sent per second!). Using echolocation does not require a single thought because it is strictly a sense; it happens naturally! Just to give you an idea about their echo frequencies, we can hear up to around 25 kilohertz. Dogs can hear up to 40, maybe 50. Dolphins produce, and hear, sounds up to 150 kilohertz! If their is another dolphin or tooth whale in the area, they can adjust their echos so that they can decipher between their and the other animal's.

Q: Can fish tell when echolocation is being used on them?
A: Fish cannot hear a very high frequency, so they may not hear the echos that are produced. However, they have a better chance of hearing the echos if it bounces off their swim bladder. (Tissue is similar to the density of water) If a dolphin is by itself and wants to surprise a school of fish, it may not send out echos so that it won't give out its location. However, if it is a pod of dolphins, they will use echolocation to locate the school of fish because there is more of them to trap the fish.

Q: Does echolocation vary between fresh and salt water?
A: No. It is just as useful in both kinds of water.

Did You Know....? Whales are linked to hippos and hoofed mammals (cow, deer, etc.).