Evolution & Behaviour

"It always seems impossible until it's

done."

14 Communication
 Communication in Animals Evolution & Behaviour

Social interactions are largely based on the exchange of signals and cues in the form
of sounds, smells, movements, vibrations, electrical impulses and visual patterns

Transfer of information from one animal to another is known as communication.

The sender and receiver in a communication may be of the same

species or of different species.

Study of animal communication is called zoosemioties.

 Evolution & Behaviour

The various means of communication in animals:

• Visual
• Chemical
• Auditory
• Tactile and Electrical
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Characteristics of Different Sensory Channels for Communication

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1. Chemical signals:

• Communication through chemicals.

• Molecules used for chemical communication between

individual animals of the same species are called
pheromones.
 Evolution & Behaviour

Example 1
• Mate attraction pheromone of the female
silkworm moth

• Male moths as far as several kilometers

downwind are informed by these molecules
that a female of their species is sexually
receptive.

• By orienting to the wind direction and

following the concentration gradient of the
molecules, they can find her
Evolution & Behaviour

Example 2

• Male elephant have temporal glands

which produces scent to indicate
their readiness for mating
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Example 3

• Male musk deers have musk

glands located at the end penis;
liberate the pheromone called
muskone that is used to mark
territory and also attract females.
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• Example 4 - Territory marking

• Pheromone messages left by mammals such as

cats and dogs, can reveal about the signaler:
species, individual identity, reproductive status,
size (indicated by the height of the message),
and when the animal was last in the area
(indicated by the strength of the scent)
 Pheromones Evolution & Behaviour

The term ‘pheromone’ was coined by Karlson and Butenandt in 1959.

All insects, animals and humans.
Pheromones are species specific
Pheromones stimulate an attractive response.
Animals detect pheromones through the Jacobson organs.

Types of pheromones :
a. Territorial pheromones e.g Dogs, Tigers
b. Trail pheromones e.g. widespread in social insects, bees,
c. Sex pheromones termites and ants

d. Aggression pheromones
e. Alarm pheromones
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Sex pheromones
Females for breeding
Sex pheromones to attract mates
Bombyx mori (bombykol)
Gypsy moth Porthetria dispar (glypleure)
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Advantages of Chemical signal

• It is most durable signal.

• It helps to establish hierarchy, dominance, grooming and bonding

between animals without much harm.

• It is effective over distance and around corners.

• Chemical signals also convey the level of aggression or submissiveness

in members of a society, thus they act as warning signals.

• This reduces excessive aggression, blood-shed and loss of life and thus
maintains the integrity of the society.
 Evolution & Behaviour
Limitations

• It cannot be rapidly changes, pheromone being volatile has to be

release again and again over a period which required expenditure of
energy.

• Diffusion of chemical signals is dependent on wind so cannot be

carried out in direction opposite to wind.

• The odour may also attract predators.

 Evolution & Behaviour
2. Visual signals

• Light signals detected by the eyes come into this category- like gestures, postures,
and facial expressions, courtship and aggressive displays in many birds, fish,
amphibians and mammals, raising of hair and colour change are some of the good
examples of visual communication.

• Visual Communication can be a structural adaptation - badge

• It can be a behavioral adaptation - a display

 Evolution & Behaviour

दम है तो आजा ..!! Example 1

• A male fiddler crab waves his

major claw rhythmically to
attract females and threaten
other males, and also uses it to
fight other males over burrows
where crabs mate and breed.
Evolution & Behaviour

Example 2

• Animals often communicate using

structural adaptations like the bright
yellow color of the male American
goldfinch.

• A structural adaptation that is used to

communicate is called a badge.
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Example 3

• The male white-tailed deer has antlers.

• The size of the antlers is a badge that can

tell another male deer how powerful the
other deer is.

दे खता क्या है ?? निकल… • The larger the antlers, the more powerful
the deer.
 Evolution & Behaviour

हुं िा मै … !! Handsome Example 4

• Many male bird's, like the northern cardinal,

have brightly colored feathers.

• The brighter a male birds feathers, the healthier

it is.

• Healthy animals make better mates than the

weaker animals, because their offspring will be
stronger and better able to survive.
 Evolution & Behaviour

आपुि बहत Danger है Example 5

बच के रहिा आपुि से • The gila monster's bright orange
colored splotches are a warning to
predators that the gila monster is
poisonous and they should back off.
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Displays

• When an animal exhibits a behavior that can be seen by other animals, it is called a display.

• Displays can be used to attract a mate or to warn off a predator

Evolution & Behaviour

Example 1:

When a male peacock opens its tail

feathers and show courtship dance,
trying to attract the attention of a
female, that is a display.
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Example 2:

Wolves and dogs put their tails between

their legs and lie on their backs to show
submission to another wolf or dog and to
let them know they are not a threat.
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Example 3

• Fireflies, for example, use an

enzymatic mechanism to create
flashes of light. By emitting
flashes in species-specific patterns,
fireflies advertise for mates at
night.

• Useful during night

Evolution & Behaviour

Example 3

The male stickle back fish turns bright red

on its belly with brilliantly iridescent blue
eyes.
 Evolution & Behaviour
Sign Stimuli
The Study of Instinct, Tinbergen (1951)
From heterogeneous summation to Gestalt-perception in 24 babies at different ages.

Heterogenous summation

Gestalt principle

Supernormal stimuli

Sign stimulus
 Evolution & Behaviour

Heterogenous summation: the law that states that a whole is equal to the sum of its parts

Gestalt principle: a whole is greater than the sum of its parts.

Supernormal stimuli: an artificial or exaggerated stimulus that triggers

a more intense response than a natural
stimulus.
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Heterogenous summation
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Gestalt perception
 Evolution & Behaviour

Supernormal stimuli Supernormal stimuli

 Evolution & Behaviour
Advantages of Visual Behavior
• Visual signals are fastest mode of communication and most effective in short distance
communication to send precise and unambiguous message.

• It is effective in all direction and independent of wind.

• Visual signals are easy to produce, come in an endless variety, can be changed rapidly, and
clearly indicate the position of the signaler.
 Evolution & Behaviour
Disadvantages of Visual Behavior

• The receptors of the receiver must be focused on the signaler, or the message will be missed.

• Most animals are sensitive to light and can therefore receive visual signals, but sharpness of vision
limits the detail that can be transmitted.

• The complexity of the environment also limits visual communication.

 Evolution & Behaviour

3. Auditory signals

• Sound is the most used form of communication in animals.

• Sounds are waves of alternating pressure changes that pass through a medium; air, water or
solid

• It's one of the most widespread forms of communication in the animal kingdom,
used by a vast array of species from insects to birds to mammals, including humans.
Evolution & Behaviour
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1. Infrasound : Low frequency sound

• Nearly human hearing range 20 Hz

• Long-Distance Communication
• Navigation and Orientation
• Predation and Defense

• Can produced by animals as well as volcanos, earthquakes

e.g : Elephant, Whale, Rhino, Giraffe, Tiger, Lion

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Functions of Auditory Communication:

• Mate Attraction

• Territorial Defense

• Alarm Calls

• Coordination and Social Bonding

Infrasound ( Less than 20Hz ) Evolution & Behaviour

Example 1
• Elephants, One of the most well-known
users of infrasound, elephants produce these
low-frequency sounds to communicate over
distances as long as several kilometers.

• These sounds are used for coordinating

movements, signaling distress, mating calls, and
social interactions within the herd.
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Example 2

• Many whale species,

including blue whales and fin
whales, use infrasound to
communicate across vast
ocean distances.

• Their calls can travel hundreds

of kilometers underwater,
allowing them to maintain
contact with each other in
Human Hearing range (20Hz to 20Khz) Evolution & Behaviour

Example 1

• Insect vibrates various parts of their

body to produce sound.

• Crickets produce loud sound by rubbing

the hind legs with their wings. This is
called stridulating.
Evolution & Behaviour

Example 2

• The rattle of this rattlesnake is

used to communicate with other
species.

• The rattle is a warning device for

predatory animals that might be a
threat to the rattlesnake.

• It produces a signal to drive them

away.
Acoustic adaptation hypothesis : Evolution & Behaviour

• The idea that the acoustic

properties, such as pitch, of
auditory signals are shaped by
habitat structure.

• Birds in heavily vegetated

habitat produces low frequency
sounds.
Evolution & Behaviour

Birds in grassland produces

high frequency sounds for
communication.
Evolution & Behaviour
Ultrasonic sounds 20 KHz – 1 MHz Evolution & Behaviour
Example 1

• Nearly all species of bats use echolocation

to navigate and hunt in the dark. They emit
ultrasonic calls and listen to the echoes that
bounce back from objects (including prey)
to determine their location and size.
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Example 2

• Dolphins Known for their sophisticated

use of echolocation, dolphins emit
ultrasonic clicks to explore their
environment and hunt underwater.
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Advantages of auditory signals

• Sound can be used at night and in dark environments.

• It can go around objects that would interfere with visual signals, so it can be used in complex
environments such as forests.

• It is better than visual signals at getting the attention of a receiver because the receiver does not
have to be focused on the signaler for the message to be received.

• Like visual signals, sound can provide directional information, as long as the receiver has at least
two receptors spaced somewhat apart.
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To understand the singing behaviour in songbirds, the following three characters were measured as
shown in the graph:
A. Territoriality rate Which one of the following conclusions is most appropriate ?
B. Female fertility rate
C. Song rate (1) Male birds sing as a display of strength to rivals and to attract females
(2) Male birds sing to display parental care behaviour
(3) Male birds sing only to display that females are sexually receptive
(4) Male birds sing only to deter other male rivals from competing for
territories
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If bird song is selected to maximize broadcast range and to minimize degradation, then according to
the “Acoustic Adaptation Hypothesis” which of the following combination of features is likely to be
shown by birds singing in dense forests?
(1) Low frequency with narrow bandwidth
(2) High frequency with narrow bandwidth
(3) Low frequency with wide bandwidth
(4) High frequency with wide bandwidth
 Evolution & Behaviour
When the electrical response of the two receptors A1 and A2 in a noctuid moth that was
exposed to a variety of sounds was measured, it produced the following patterns:
Given this, which one of the following
statements is INCORRECT:
(1) The A1 receptor is sensitive to sound of
low to high intensity.
(2) A2 receptor begins to produce action
potentials only when a sound is loud.
(3) Both the receptors have similar response
to high intensity sound.
(4) The Al receptor fires much more
frequently to steady, uninterrupted
sounds than to high frequency pulses of
sound.
 Evolution & Behaviour
Males of a species of grasshopper produce loud calls to attract females. Most energy of these calls lie in the species-
specific frequency, while other frequencies have much less energy. This is depicted in a power spectrum (plots with solid
line in the figures below). Females find males by listening to and recognizing the species-specific call, and they are most
sensitive to the species- specific frequency. This is depicted using hearing threshold curves (plots in dashed lines in the
figures below). This allows females to find even the softest calling males of their own species and ignore even the loud
callers of other species, resulting in reproductive isolation.
Which one of the following figures represents the correct option for the hearing threshold (dashed lines) of females,
given the power spectrum (solid lines) of male calls of this grasshopper species?
 Evolution & Behaviour

Many species of birds call at dawn in temperate regions. The phenomenon is referred to as
"Dawn Chorus". Several explanations have been proposed for this. Which one of the
options is NOT a correct explanation for the occurrence of "Dawn Chorus"?
1. Transmission of sound is better at dawn due to colder temperature at that time.
2. Singing at dawn is costly as the birds are low on energy. This makes singing at dawn a
handicap and thereby indicates honest signalling.
3. Dawn chorus allows birds to utilise a time window for singing which does not interfere
with their feeding time.
4. The syrinx muscles are unable to move freely after early morning, resulting in poorer
control over song production at later times of the day.
 Evolution & Behaviour

A researcher studying crickets finds that individuals on either side of a large river have different
call frequencies on average. Which of the following statements are true, assuming the call helps
attract mates ?
A. The different call frequencies might signal the start of new species forming.
B. The change in call frequency could cause the formation of new species.
C. Crickets moved from one side of the river to the other may have a harder time finding mates.
D. The call frequency changes from ultrasound to infrasound across the river.
(1) A, B, and C
(2) A, C, and D
(3) B, C, and D
(4) A, B, and D
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An extraordinary sensory ability that elephants possess is.

(1) emission and detection of ultra-high frequency sounds.
(2) emission and detection of ultra-low frequency sounds.
(3) detection of changes in earth's magnetic field.
(4) possession of ultraviolet vision.
 Evolution & Behaviour
4. Tactile / Mechanosensory communication

• Communication involves the use of physical touch to convey

information between individuals.
• More common in social insects.

e.g Blind workers of termites

Blind fishes
Dance of honeybees
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तू बुड्ढा हो गया है ….नबडु

तूिे हाथ कैसे लगाया ??

 Honey Bees CommunicationEvolution & Behaviour
Waggle Phase The bee moves forward in a Round dance is typically used when a
straight line, vigorously wagging its body and food source is very close to the hive,
vibrating its wings, then circles back to the usually within about 50 to 100 meters
starting point to repeat. Distance is more than 100
meter
(about 160 to 330 feet).
Evolution & Behaviour

Example 1

• When a forager bee finds food, she

returns to the hive and
communicates her discovery to her
hive mates by dancing in the dark on
the vertical surface of the
honeycomb.

• The dance is monitored by other

bees, who follow and touch the
dancer to interpret the message.

• Dance conveys information about

both the distance (Odometery) and
the direction of the food source.
Evolution & Behaviour
 Evolution & Behaviour

तू मेरा प्यारा बेटा है िा..!! Example 2

Social bonding and grooming:

Many animals, like primates, groom

each other to strengthen social
bonds and hierarchies.
 Evolution & Behaviour

Example 3

Nurturing and care:

Mother animals often lick or nuzzle

their young ones to show care and
comfort.
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5. Electric Communication

• Some species of fish have evolved the ability to

generate electric fields in the water around them by
emitting a series of electric pulses.

• These trains of electric pulses can be used for

sensing objects in the immediate surroundings, and
they can also be used for communication
 Evolution & Behaviour
Elephant - fish Torpedo Rays Some freshwater dwellers in
Africa and South America, like
the elephant-fish and the knife-
fish, are the champions of electric
chit-chat.

Knife - fish

eel
 Evolution & Behaviour
How it works:

These fish generate their own electric fields using special organs.

They can then sense distortions in this field caused by other electric fish or nearby objects.

This bio-electric messaging is quite subtle, with info encoded in the frequency, waveform, and timing of
the electric pulses.
 Evolution & Behaviour

Advantages of electric chat:

Electric communication works well in murky or noisy water where sight and sound might
be unreliable. It's also private, as most creatures can't perceive these electric signals.

This secrecy allows electric fish to communicate without tipping off predators or
competitors

Electric signals are thought to convey a variety of messages. They might be about finding a
mate, establishing dominance, or just identifying each other's species.
Evolution & Behaviour
 Evolution & Behaviour

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