Like bats, dolphins echolocate
to navigate and hunt. The ability to echolocate (also called biosonar) was first identified by Jaques-Yves Cousteau in
1953. Echolocation is produced differently than vocalizations (described elsewhere in this site - see "Blowhole &
Breathing" and "Vocalization" sections). The dolphin's echolocation system is used to detect, discriminate and recognize underwater
In this video, a Bottlenose dolphin uses its vision and echolocation
system to navigate around and through a man-made coral reef in a captive dolphin habitat.
buried in the ocean sediment are also "visible" to the echolocation system. Importantly, it can function in both the
quiet and the noisy ocean environment.
echolocation system is divided into three major subsystems: transmission (by tissues in the melon), reception (by
the teeth and lower jawbone), and signal processing/decision making (by the brain).
The echolocation system is not functional
in the newborn calf. Consequently, the mother will "steer" the calf away from objects which could cause it harm. Often, in
captive environments, calves are born in "structureless" pools which protect them from inadvertent injury. A calf begins to
show signs of transmitting echolocation clicks as early as 2 months after birth. The more complex the environment
in which a dolphin finds itself, the more complex the echolocation signals emitted. The size, shape, direction, speed, distance
and composition of an object as small as a ping pong ball as far away as a football field (100 yards) can be detected by the
dolphin’s echolocation system. Echolocation may also function socially as a method of identification between mother
and calf or between individuals within a pod.
research on echolocation is extensive, much of our understanding of it remains a mystery. Dolphins produce echolocation sounds
that are either harmonic or pure in tone and are of changing frequency. A "train of clicks" is produced in echolocation. Each
click in the train is of very short duration. Anywhere from 8 to 2,000 echolocation "clicks" may be emitted per second. This
short duration allows the click to go out, strike an object and return to the animal before another click is produced. This
prevents the mixing or confusion of click signals received by the dolphin. The time between clicks in a particular train changes
as the animal approaches an object, as it must adjust for distance to its target. Short duration, high frequency clicks also
allow it to focus on small fish and small obstacles, but they don't travel as far in water as do low frequency sounds. That
is why communication between marine mammals is usually done with sounds of low frequency. A dolphin may turn its head from
side to side when echolocating to provide further information about the target size and direction. When used to stun fish
for feeding, echolocation clicks may be produced as loud as a booming 230 decibels, representing some of the loudest sounds
made by animals in the ocean. It
has been shown, though, that if a dolphin’s eyesight is impaired (by covering its eyes) its echolocation system is less
effective, proving that echolocation and eyesight work in tandem. Recent research suggests dolphins can "eavesdrop" on other
dolphins' echolocation returns, at times stealing a fish from a competitor. Recent studies show dolphins have the ability
to echolocate an object within another object. In other words, when an object of one density is placed inside an object of
lesser density, the dolphin can visualize the interior object (much like ultrasound).
Clicks produced by the dolphin's phonic lips (also called "monkey lips) or air sacs in the nasal passages,
pass through the fatty tissue of the dolphin’s melon. This melon tissue acts as a focusing lens to project these clicks
outward as a beam. This sound beam of clicks travels well through the salt water and strikes an object. The sound beam returns
back to the dolphin's reception subsystem, the teeth and fatty tissue in the lower jaw bone (the panbone), where it is sent
to the inner ear bones. The auditory nerve leading from the inner ear then transmits these signals to the mid-brain for
rapid processing and decision-making about their meaning. The dolphin produces sound at frequencies up
to 120 khz. Compare this with the ability of man to hear frequencies only up to 20 khz and dogs only up to 45 khz. If
a dolphin were to echolocate on us while in the water, we would feel the "buzz" of the sound waves although we would hear
Some man-made sounds in the ocean interfere with dolphin echolocation and are capable of causing hearing loss,
disorientation, stranding and brain hemorrhages to the dolphin. These man-made sounds are called "arthropogenic noises"
and include acoustic testing, off-shore drilling and Naval sonar use by submarines.
Understanddolphins.com contains information condensed from a number of reputable technical sources,
peer reviewed journal articles, and respected dolphin research facilities, as well as from my personal experiences and
observations as a dolphin VIP Tour Guide and Educator.
I have made every attempt to support the information presented in this site with video and still
photographic images. On a regular basis I plan to produce more of these images and will continue to update the site with these
as well as with any new and scientifically verified information which becomes available.