COMM
141
Term
Paper
It
is the vibration of your eardrum that causes what we refer to as sound.As
humans, we are only able to detect sounds that vibrate between 20 and 20,000
times per second.Animals, however,
have various other ranges of listening.There
are many animals that communicate using infrasound and ultrasound.The
human ear alone cannot hear the slower vibrating sounds and infrasonic
messages of certain animals.It is
the same scenario for ultrasonic communication between animals.These
are not in our natural hearing range, however, with the advancement of
bioacoustics and technology, researchers are beginning to understand and
study the communicatory methods of animals.
Auditory
stimuli can influence an animal’s behavior in a number of ways.According
to Nicholas Collias, animal sounds are classified into “four ecological
categories:avoidance of enemies,
food problems/hunger, reproduction, and group movements” (Lanyon, pp. 368).
“Parent
birds often use food calls that stimulate the feeding reactions
of the young” (Lanyon, pp. 368).Younger
animals may also use care calls in order to let the parent know they are
in need of some type of help.Predatory
animals also use special hunting/food-findingcries during the hunt
and after a kill.The Grey wolf,
for example, makes three different hunting calls, each with its own significance.The
first is a long howl, alerting the rest of the pack that the hunt is on.The
second howl has a higher pitch, indicating that a fresh trail has been
found.The final call, a mix of barks
and howls, means to be “closing-in” on the prey.In
the case of Humphrey the humpbacked whale, researchers had to lure
Humphrey back out to the ocean after swimming more than fifty miles up
the Sacramento River.Due to some
whale vocalization studies, the rescuers used a recorded whale feeding
sound to lure the whale back out to the ocean.
An
animal’s acoustic signal can sometimes be the difference between their
life and death.“The determination
or the origin of the signal may be as important as its recognition” (Brown,
pp. 145).If the prey’s location
is unaware to the predator, due to their vocalizations and/or location
being unknown, they have a much better chance for survival.Due
to the “upper range of hearing that cats (50 kc), rats (40 kc), and certain
other rodents possess, the supersonic cries of their prey can be heard
and used as clues in the hunt” (Lanyon, 370).
Animals
also use sound to alert any other potential prey of danger.Animals
of different species even “heed the warning cries of other species” (Lanyon,
372).Many birds, for example, use
different calls for different types of predators.They
have a designated call for aerial predators and another for those on the
ground.Smaller birds use a very
high-pitched squeak to alert others that there is a hawk in the vicinity.These
high-pitched sounds are very hard for a predator to locate, while causing
any potential prey to take cover.The
California ground squirrel has its own kind of warning chirps.They
are more or less specific for hawks, snakes, and mammalian predators.
Animals
also communicate with others of their species vocally.Many
migrating birds rely on contact notes between the flocks.These
keep flocks together, and are used to indicate starting and stopping (Lanyon,
380).When paired birds are separated
from each other, they use localization calls to give their position.“The
loud honking of Canada geese serves to keep the flock together in the air”
(Lanyon, 380).Howling monkeys practice
the same, giving off a deep grunting sound in order to keep the clan together
while walking through the dense forest vegetation.In
the penguin species, they recognize each other using the display call.Porpoises
and bats use clicks to navigate in order to prevent collision with any
others and in places of low visibility.Male
mosquitoes can hear through their antennae, and can locate the buzzing/hum
of their mate, as well as stick together in swarms.
An
individual animal can be identified by their vocalizations “only by using
a combination of temporal and frequency characteristics.These
characteristics can be constructed to allow individual recognition by fellow
group members, distinguish certain populations from others, and localization,
which allows the caller to compensate for the distance to the receiver”
(Snowdon, pp. 235).Dolphins produce
many whistles, ranging between 5 and 20 kilohertz, which last about a second
in length.They use the whistles
to maintain contact with other dolphins and in directing school swimming.Each
dolphin’s whistle has its own distinctive variation in frequency, which
remain unchanged for the majority of their lifetime.These
frequency-varying whistles act as an identifier of individual dolphins.These
distinct whistles may also describe certain emotions of the dolphin by
changes in their pitch and duration.
Some
species use sound to facilitate mating rituals and interaction.Most
often, it is only the male who calls, but in some species, both sexes practice
mating calls.They elicit sounds
in order to make others aware of their sexual status and location.With
moths, ultrasonic communication plays a vital part during courtship.Males
fan their wings “between 41 and 72 pulses per second, with a frequency
range of up to 80 kHz” (Ambientali).For
the Mosquito, the female sends out her sexual signal, inviting any males
in her proximity into having a sexual relationship.Certain
birds have territories that take on some kind of sexual importance during
mating season.The male birds tend
to use their songs to defend their territory against other birds of the
same species.These songs also attract
females looking for a mate.In certain
frog species, a frog’s sex is not obvious due to just its physical appearance.There
are times where males may have mistaken other males for females, mounting
them in hopes of mating.The captive
male will let out a “warning signal or grunt”, making the courting male
aware of his mistake (Lanyon, pp. 176).The
courting males quickly release the captive males, since females make no
sound during the mating process.
Sounds
lose quality over long-distances, especially through natural habitats,
whereas the trees and background noise compete in muffling sounds.Many
animals must communicate in such places and do so well.These
extremely noisy conditions include various insect sounds, wind noise, and
sound of other species, along with the other various sounds of nature.
Elephants
and Rhinos use infrasound to communicate over long distances.It
differs from ultrasound in regards to its wavelengths being too long, which
would be of no use on small objects (Busnel, 184).This
is sound below the range of human hearing, and can be heard through miles
of plains and forest.When a member
of the group is separated from the rest of the group, they “have the ability
to coordinate their patterns of movement for weeks at a time without losing
communication or converging on the same scarce resources.Many
female elephants use their infrasonic voices to attract mature male elephants
from all over.This is very important,
since the female may be only receptive for four days out of every four
years.Some animals even use infrasound
as weaponry.Taking the form of pressure
waves, certain whales use infrasound to stun their prey, paralyzing them,
leaving them helpless.Researchers
describe it as being hit by an “invisible wall from which there is no escape”.
There
are many animals that use a type of ultrasonic clicking called echolocation,
which refers to the behavior in which an animal produces vocal sounds and
then listens to the echoes returning from the objects that reflect these
sounds.Echolocation clicks penetrate
solids in the same manner as an ultrasound device.Animals
can control the amplitude of these various clicks, using the lower frequency
scans to get an overall picture of its surroundings, and then switching
to higher frequencies in order to get a more in-depth look.The
clicks of a dolphin are broadband pulses, ranging up to 150 kilohertz,
which are focused into beams through fatty tissues in the animal’s forehead.“They
send, receive, and process up to 700 clicking sounds per second to detect
the size and location of an object hundreds of meters away,” (Newton’s
Apple, #1307).The dolphin’s echolocation
is sensitive enough to detect a three-inch ball from 100 yards away.
Dolphins
communicate using the same acoustic sense with which they perceive, while
humans depend mostly on acoustic representations for communication.For
bats, sight plays a very small part in hunting for prey.They
must use echolocation instead because if they had to rely on sounds of
their prey, the bats would have to be almost totally silent themselves.A
bat emits its clicks, which are reflected off of small objects back to
their super-sensitive ears.This
allows the bat to locate its distance from the ground and other objects.
Bats
cannot distinguish whether small objects are food or not.They
use a higher frequency when hunting insects because small objects reflect
the short wave lengths much easier.Researchers
often confused the bats by throwing pebbles in the air, which the bats
mistaken for prey.Several small
nocturnal insects however have the ability to hear the echolocation clicks
of bats and use them to avoid becoming the bat’s prey.When
they hear the echolocation clicks of the bats, they know to go into some
kind of evasive maneuvers.Even dogs,
which are sensitive to ultrasonic sound, use this to avoid an approaching
vampire bat.
Bats
also use echolocation for navigational purposes as well as to find their
insect prey.Bats, when flying several
meters from the ground, emit click wave trains 3 to 5 meters long.“The
rhythm of clicks may vary from 4 to 10 per second, depending on the distance
from the ground” (Busnel, pp. 197).This
enables bats to locate the ground, trees, and other objects at certain
distances.Some bats emit clicks
that are of low intensity and very high frequencies.These
animals usually tend to feed on non-moving prey such as fruit or sleeping
animals.
There
are also those animals that reside in the areas of the ocean too deep for
light to travel.These animals use
echolocation to move around in turbid water, where it is almost impossible
to see because it is so dark.They
also use echolocation to find prey and to strengthen their own survival
skills.For example, some fish can
tell the location of certain fishing nets, even in water too dark to depend
on vision.
We
are beginning to understand and realize the differences in communication
of animals and how they have adapted to their environment and surroundings.It
also helps us to understand the differences and similarities between the
rest of the natural world and ourselves.These
studies have various uses in society and allow us to understand more about
our animal neighbors and how we should interact as a whole.
References
Bioacoustics:http://www.ornith.cornell.edu/brp/
Bioacoustics
Team:http://www.cb.u-psud.fr/cb/
Busnel,
R.G. Acoustic Behavior of Animals.Amsterdam,
New York,
Elsevier,
1963
Center
for Bioacoustics: http://www.unipv.it/cibra/
Center
for Sound Communication:
http://www.ou.dk/Nat/biology/neuro/CSChome-eng.html
Dolphin
Communication:http://www.eecs.umich.edu/~coalitn/sciedoutreach/funnex…/dolcom.html
Dolphin
Research:
http://www.dolphin-institute.com/research/dolphinres.html
Lanyon,
Ed.Animal Sounds and Communication.Washington,
American
Institute
of Biological Sciences [c1960]
Snowden,
Charles T.Primate Communication.Cambridge
University Press
1982
Snowden,
Charles T.Social Influences on
Vocal Development.Cambridge
University
Press 1997
Todt,
D.Primate Vocal Communication. Springer-Verlag
Berlin
Heidelberg
1988