| |
CETACEANS SENSES AND ECHOLOCATION
Echolocation:
Echolocation is ability that cetaceans (Dolphins, whales, and porpoise) share they use this mainly for haunting for their prey, in a sense this ability allows the dolphin to able see with their ears.
By producing clicking sounds the clicks pass through the head of the dolphin called the melon, the sound wave reflect off objects for instance fish, then return to the dolphin.
The melon acts as an acoustic lens focusing the sound waves into a beam which is projected forward into the water, and when the beam or signal returns its is received by the lower jaw up to the middle and inner ear.
The brain receives the sound as a series of nerve impulses, which allows the dolphin to interpret or read the signals.
Echolocation can determine speed shape distance and even size of the object; they are even able to recognize the echo signals of their favorite food.
Dolphins produce clicks each lasting 50-128 microseconds. |
| |
Hearing
Dolphins have a very acute sense of hearing; their inner hearing nerve has twice as many fibers than human’s equivalent. Dolphins respond to higher tones within a frequency range of 1-150Hz / 0-217Hz, they have small openings just behind the eyes. Dolphins inner ear is incased in a separate bone, connected to the skull with fibrous tissue meaning it is isolated from the skull. A fat filled cavity in the lower jaw bone and appears to conduct sound waves through to the bones in the inner / middle ear. Sounds are received and conducted through the lower jaw to the middle, inner ear then to the hearing centers of the brain via the hearing nerve. Their middle ear cavity is filled with a highly vascularized tissue supplied with blood which adjusts the pressure within the ear when the dolphin dives.
Eyesight
Dolphins have an acute vision in and out the water but mainly adapted in the water, their retinas in the (center of the eye) have two central images that receive images, as we humans only have one.
This means they have binocular vision and monocular under the water, their eye's respond also to low light levels indicating they can see in these dim light conditions.
It is believed that dolphins vision is capable of see color in their marine world, as some animals do not have this capability.
|
