BIOLOGY
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communication
EXTENSION ACTIVITY
More about Vocalisations in Animals
A common feature of most animal vocalisations is that the sound is repeated over and over, with little
variation
Invertebrates
Most invertebrates do not produce sound. Humans notice invertebrate sound production most in
Phylum Arthropoda. Arthropods, such as crustaceans, arachnids and insects play their bodies like a
musical instrument by using their exoskeletons.
Crustaceans make sounds by tapping or rasping their exoskeletons. Rasping is similar to stridulation in
some insects and is used to lure a mate. Some lobsters achieve a sound by rubbing the end of their
antennae on the shell between their eyes. When ready to mate, a male crab lifts its large claw and rubs
the ridges against his shell. This noise is irresistible to female crabs. The Pistol Shrimp lifts its
oversized claw and snaps it with a noise loud enough to stun its prey.
Insects The singing of cicadas, crickets, etc., is simpler than birdsong as insects are relatively
insensitive to pitch. (see text)
Male mosquitoes beat their wings in a certain frequency to produce the equivalent of a "wolf whistle".
If a female is receptive she will then respond with a gentle buzz with her wings. They actually produce
three different frequencies. The lowest frequency is used in courtship.
Flies use a technique similar to mozzies, except that the female can be no further away than one
centimetre away to be able to detect the serenade.
Arachnids Spiders may stridulate by rubbing their legs in their pedipalps, two leg-like organs near the
mouth. Some males actually pluck the strands of the female's web like strings on a harp.
Glenda CHIDRAWI Marilyn MERCER
BIOLOGY
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communication
Fish
Sounds made by fish vary, for example, minnows purr; cod grunt and haddock resemble a motorbike
engine.
Stridulation works particularly well under water and is utilised by fish in various ways. They may do
this by rubbing together teeth, fins and/or bones. Triggerfish use their dorsal fins. Sea catfish squeak
when they flex their "pecs".
Male drum fish use special muscles near the swim bladder to produce sounds similar to a drum roll. To
attract a mate, male damselfish also flex muscles attached to the swim bladder to produce a chirping
sound, which increases in rate as a female approaches. This changes to a popping sound if another male
comes along.
Amphibians
The first organisms to inhabit the land also developed the first voices. Air could be forced over the
vocal cords. Frogs and toads use almost as much energy in making species specific calls as they do in
locomotion.
Female toads have a preference for larger suitors with deep voices (croaks). Changes in temperature
can change the pitch of a croak. So some smaller males cheat. American Fowler's toads have learnt to
move to cooler parts of the pond to deepen their sounds and so compete with larger rivals.
Newts and salamanders, except for the odd squeak, are basically mute. They rely on smell.
Reptiles
For most reptiles their vocalisation is simply a loud hiss produced by quickly expelling air from the
lungs. The rattlesnake makes its distinctive whirring sound by shaking the bones in its tail rattle. The
sound is mimicked by harmless snakes. To do this rat snakes vibrate their tails among dry leaves. The
action of the dangerous saw-tailed viper, by rubbing its side scales together, is also imitated by
harmless snakes.
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BIOLOGY
OPTIONS
communication
Researchers believe that cloacal popping could be widespread among snakes. The sound is produced by
contracting the cloacal sphincter, which forces the air out. Multiple pops are created by relaxing the
sphincter to draw air in, then contracting it again.
Table: Comparison of two cloacal poppers
Cloacal Popper
Number of pops
Amplitude
Frequency
Structures
Sonoran coral
Consistent,
Low, about 50dB
442-5523 Hz
Large cloaca,
snake
evenly spaced
Western hook-nose
variable
snake
small sphincter
Loud, about 70dB
359-15178 Hz
tapering to 50dB
Small cloaca,
large sphincter
Birds
Sound can sometimes be the only form of communication for birds that live in dense forests or in
marshes, while those from more open areas can combine this with visual displays.
The syrinx is a bird's highly developed singing instrument found at the base of the windpipe. (See text).
Vocalisations can range from the soft cooing of doves to the loud laugh of the kookaburra or the
territorial screeching of the magpie. Cranes, geese and swans are also able to modify their sounds
(honking) because of their long necks and subsequently their elongated windpipes. Some birds, such as
the pelican and the cormorant, are mute.
At the start of the breeding season the testes of the male birds pump out hormones, which initiate a
courtship song. The ovaries of a canary will not develop until she hears the male's song.
Glenda CHIDRAWI Marilyn MERCER
BIOLOGY
OPTIONS
communication
Mammals
During the winter breeding season hundreds of humpback whales congregate. They sing songs, which
have been recorded as having up to 8 themes of repeated phrases. Each song can take up to 20 minutes.
A session can last as long as 22 hours. The songs vary from pod (group) to pod, with each member
singing a similar song. At the beginning of each season parts of the previous year's song can still be
heard but this evolves as time goes on. The songs can be heard up to 32 kilometres away.
Fin whales spend most of their time under pack ice. Their sounds can travel under the ice for several
hundred kilometres if they utilise submarine terrain and icy water currents.
Elephants emit some sounds that are barely audible to the human ear: 14 to 24 Hz. These rumbles are
called infrasound and can be heard over 20 km. They are used in many ways for communication such
as greeting, contact, suckle time and move off time. If a calf is in danger it will scream, causing the
herd to come running and producing one of the loudest infrasound rumbles to act as a deterrent.
Elephant herds are made up chiefly of females (cows) and their calves. The males (bulls) are solitary
and so move away from the herd. A cow is ready to mate for only a few days every 5 years. When she
is on heat, she calls to passing bulls by using infrasound and they come running, grumbling a "musth
rumble" (musth: when a bull is ready to mate; has high levels of testosterone and very aggressive).
Battle then ensues between the bulls to determine which one has the right to mate with the receptive
cow. The cow and bull then rumble back and forth to each other. She bellows her loud song and they
mate. After mating the cow starts a post-copulatory rumble, which causes the whole herd to rumble,
trumpet and defaecate. Researchers refer to this as "mating pandemonium".
Deer stags roar at each other to test the other's strength and thus avoid an antler- to- antler
confrontation. The contest is won by the stag that bellows the most roars per minute.
Glenda CHIDRAWI Marilyn MERCER
BIOLOGY
OPTIONS
communication
Primates use vocalisation, not so much for courtship but as a means of keeping groups together and
warning of danger. Gibbons have a song, which occupies a very limited frequency range. They
compress their sound signal so that it penetrates the jungle for long distances. They use the laws of
physics by mostly calling at dawn when the air is cool. The Siamang, the largest of the gibbons, gives a
deep boom from two resonating throat pouches.
Vocalisations in animals are many and varied. This is a brief summary of a few and may generate
interest for further research on this subject.
Activities:
1. Use the information given to discuss why sounds made by animals must be repetitive, species
specific and easily recognisable.
2. Produce a sequenced flow chart to summarise vocalisations of elephants.
3. Demonstrate how the type of sound produced relates to the structure of the animal by comparing
named invertebrates with named vertebrates.
4. Account for female frogs producing a "release call" after copulation.
Glenda CHIDRAWI Marilyn MERCER