Introduction to Animal Behaviour

Animal behaviour is outwardly expressed action of living beings in response to stimulus at a given situation. Stimuli are physical or chemical factors such as light, temperature, pressure, electricity, gravity, chemicals etc. The scientific study of animal behaviour is called ethology. There are two types of animal behaviour they are:

• Innate or Stereotype behaviour
• Learned or Acquired behaviour

Innate or Stereotype

It is also called inherent or intrinsic behaviour. It includes an inborn adaptive mechanism by which animals adjust to the environment. Especially, lower animals show stereotype behaviour only. There are three types of stereotype behaviour:

• Orientation (Taxis and Kinesis)
• Reflexes
• Instinct (Migration)

Learned or acquired behaviour

The degree of performance in learned behaviour depends on memory gained by previous experiences. It is not inheritable.

Reflex Action

The simplest form of irritability of organisms that is associated with the nervous system is a reflex action. It is an involuntary action in response to a stimulus and action is stereotype i.e. reflex action is an inborn or inherent behaviour. In the body, there are two types of nerves which are responsible for carrying the message in the form of impulses from receptor cells to the brain and from the brain to the effector cells. These nerves are:

Reflex action is a rapid, automatic, motor response to the sensory stimulus without conscious control of the brain. It is an involuntary action and stereotype behaviour.

Mechanism of reflex action

The nervous pathway which is taken by nerve impulses to show the response in reflex action is called the reflex arc. Reflex arc comprises reception, conduction, modulation and impacts.

Reception (sensory cells) → conduction (sensory nerve) → modulation (brain or spinal cord) → conduction (motor nerves) →effects (muscles and glands).

There are two types of reflexes;

Spinal reflex

If the reflex arc passes through the spinal cord, then the action is called spinal reflex. In spinal reflex, sensory nerve fibres enter through dorsal root and motor nerve fibres emerge from the ventral root of the spinal cord. All the nerve cell bodies of the sensory nerve are found in the swollen structure of dorsal root called ganglion. The flow of impulses is always unidirectional due to the presence of synapse (junction between sensory and motor neurone). Example: Withdrawl of the foot while stepping on the pointed pin.

Cerebral reflex

If the reflex arc passes through the brain than the action is called cerebral reflex. Example: blinking of eyes, sneezing, salivation in mouth etc.

Taxis

Taxis is the movement of a whole organism in response to an external directional stimulus. Taxis is a kind of orientation in response to external stimulus. Taxis movement may be towards stimulus called positive taxis and away from the stimulus is called negative taxis. The movement of certain parts of the body in response to the stimulus is called tropism. Sessile animals and plants show tropism. On the basis of nature of stimulus taxis is of following types:

Phototaxis

Movement of an organism in response to light. Eg: Earthworm moves towards dark place (Negative phototaxis), Euglena moves towards light (positive phototaxis).

Chemotaxis

Movement of organisms in response to chemicals. Eg: Earthworm moves away from HCl which is negative chemotaxis and earthworm moves towards the glucose which are positive chemotaxis.

Thermotaxis

Movement of organisms in response to heat. Eg: Earthworm

Rheotaxis

Movement of organisms in response to water current.

Aerotaxis

Movement of organisms in response to air.

Magnetotaxis

Movement of organisms in response to the magnetic field.

Hygrotaxis

Movement of organisms in response to moisture.

Geotaxis

Movement of organisms in response to gravity. Eg: Earthworm moves deep into the soil.

Thigmotaxis

Movement of organisms in response to touch.

Galvanotaxis

Movement of organisms in response to electric current.

Taxis can be differentiated into following types:

Klinotaxis

The organism which has sensory receptor cells at the anterior end only shows klinotaxis. To stimulate both sides of the body, it moves in sidewise movement. Eg: planaria shows klinotaxis while moving towards food.

Tropotaxis

The organism which has paired sensory organs such as eyes, ears etc. shows tropotaxis. Sidewise movement is not necessary here.

Telotaxis

The bilaterally symmetrical animals show the response towards only one stimulus, not both or intermediate when two sources of stimuli of same intensity operate at the same time.

Menotaxis

Movement of organisms in response to stimulus at a constant angle.

Mnemotaxis

Movement of organisms in response to complex stimuli like landmarks, light direction etc.

Kinesis

It is non-directional movement in which rate of movement is related to the intensity of the stimulus. Eg: movement of tentacles is slow and random but when food is placed closer, the movement of tentacles increases.

Dominance

The behaviour of an animal in which one dominates to other by showing aggression or threat is called dominance. It includes both stereotype and acquired behaviour. The individual who is older, stronger and bigger dominates the younger, weaker and smaller one. Dominance is determined by age, sex, experience, morphological or physical factors. Dominance is shown by the animal to avoid the extreme condition, to get food and shelter, also for the mating purpose. Eg; In dog male during breeding season.

Leadership

It means to give guidance for the other members of a group by going before and drawing them along the same course. Eg; ant, bird, bee, sheep, deer, monkey etc. shows leadership. Leadership is shown by animals during the fighting, feeding, and migration.

Qualities of the best leader

• The leader should be mature and physically well sound.
• The leader should initiate, stabilise and integrate the members of the group for quietness.
• The leader should have the freedom of action.
• The leader should take the responsibilities of others.