The Science Of Behaviour: History, Scope And Terminology

Branches Of Ethology

Discuss various branches of Ethology.
Discuss ecological, physiological and evolutionary approaches of animal behaviour.

1. Ecology and Behaviour or Ecoethology

Ecoethology is the study of relationship between behaviour of a species and the living and nonliving components of its environment. It embraces two approaches:

1. To study the behaviour of animals of related species in their natural environments.

2. To study the behaviour of a group of species in a particular environment.

1. Study of Behaviour of a Species in Different Environments: During the course of evolution, animals become adapted to a particular environment. It means the consequences of an activity in case of a well adapted animal may be beneficial in that environment but the same activity performed in a different enviroment may be harmful. Therefore, it will be expected that if one group from the related species migrates to an entirely different habitat, its behaviour will deviate substantially from the behaviour typical for the whole group of species. It includes study of differences in the bahaviour within a single species or within a group of closely related species that occupy different habitats. Comparison of closely related species living in different habitats reveals those aspects of behaviour which are particularly important in adapting the animal to its enviroment.

2. Study of Behaviour of Different Species in a Particular Enviroment: It shows that animals belonging to different species when coexist in the same habitat, they exhibit parallel behavioural adaptations neccessary to live in that particular habitat. When animals of different species live in the same habitat, they use the same resources or have certain preference or tolerance ranges in common and their niches overlap. It means they are fighting for the same facilities. Therefore, niche overlap leads to competition. Thus, if two species coexist successfully, there must be some ecological differences between them and their niches do not overlap. The competitive excusion principle states that two species with identical niches can not live together in the same place at the same time, especially when resources are limited.

It will be interesting to study how different species living in the same area occupy different niches, differ from one another and how these differences can be considered an adaptation to different niches in the same habitat.

2. Evolution and Behaviour

The two most important characteristics of behavior are : 1. deversity of behaviour and 2. adaptiveness of behaviour. The diversity of behaviour is the result of adaptecdness for a particular life style appropriate for a particular envirinment. Adaptation is the basis of evolution and behaviour is one of the important kind of adaptation.

Two areas of ethology deal with the change of behaviour:

1. Ontogeny of behaviour is concerned with the development of behaviour in an individual.

2. Phylogeny of behaviour traces the evolutionary origin and development of behavioural characteristics in a species or in a group of species.

Like any other evolutionary process, behavioural developments also occur through small changes and stages of adaptations. In present day animals, the combination of structural adaptatuins and refined behavioural patterns have evolved through many generations, which have enabled them to survive.

Example: In screech owl, two behavioural traits for defence against predator are:

1. They are nocturnal and while roosting during day time, remain motionless comouflaging with the surrounding for protection.

2. If detected by the predator, they bluff by swelling, snapping and flapping in order to scare away the predator.

Protection through camouflaging or imitating physical structure, behaviour of a nonharmful species similar to an inedible species or by warning mimicry have evolved separately in different groups. These similarities can not evolve suddenly.

1. Orgin and Evolution of Social Behaviour in Honeybee: The origin and evolution of a behaviour can be traced by comparing behaviour patterns in closely related species and analysing how they have diverged. Karl Von Frisch studied social behaviour in many species of bees and suggested the likely course of evolution from solitery ancestor, through various intermediates of social life:

(a) There is one species of bees whose individuals are solitary. Each bee makes a burrow, constructs few cells in a tree truck, lays eggs singly and puts honey in each cell and seals it.

(b) In another bee species, the young bees hatch while mother is still laying eggs. Some of the young bees help the mother till she leaves the hive.

(c) In bumble bees, the young ones that help mother remain small and less fertilr.

(d) In the final stage, in some species, the workers remain sterile and all the castes live together in the same hive carring functions assigned to them and are modified accordingly.

2. Role of Natural Selection in Evolution of Behaviour: The role of natural selection in modifying the behaviour of closely related species can be illustrated by the following example:

Two closely related species of frog found in the southern United States have wide range of distribution. One species is more abundant on east, while other in the west. Their mating calls are remarkably similar in their areas, but in the central regions where two species overlap, they have developed quite distinct mating calls. This keeps the two species apart.

The greter part of behaviour pattern is fixed in the chromosomes. It means behaviour patterns are inherited and these can evolve along with the evolution of gene pool of a population or a species. The behaviour patterns are modified and supplemented by learning and reasoning. The final behaviour of an individual is the result of interaction of genetic make up and the environment in which an animal is developed and grown.

3. Behaviour and Physiology or Ethophysiology

This branch of behaviour is associated with physiological basis of behaviour. Behaviour is actually the result of coordinated muscle activity, guided by messages from central nervous system and hormonal system which are produced in response to from central nervous system and hormonal system which are produced in response to external stimuli and internal physiological conditions. Based on these two control systems two important fields of behavioural physiology have been recognised:

1. Neuroethology: It is associated with the neural control of behaviour and includes coordination of central nervous system, nerves neurons, sense organs and their association with muscles.

2. Ethoendocrinology: It involves the study of hormonal control of behaviour. An example of neuroethology is ingestive behaviour. The sensation of hunger (the hunger pangs) comes from the violent contractions of empty stomach. These are caused by the low level of glucose in the blood. Low glucose level affects hunger-regulating centre in the hypothalamus of brain. The impules from stimulated hunger-centre are passed on to the muscles of stomach wall, causing them to contract and produce hunger pangs. The hunger pangs motivate the animal to feed. The low glucose level in blood is the internal factor causing feeding behaviour.

Sexual or mating behaviour are examples of ethoendocrinology. Sex hormones androgens in male and estrogen in female are directly associated with sexual maturity, secondary sexual characters, courtship and mating. Hormones from pituitary, ACTH and other related peptide hormones affect male copulatory behaviour especially erection and ejeculation. LH and prolactin induce parental care, nest building, brooding and feeding young ones. Even functioning of mammary glads is controlled by prolactin. The secretion of these hormones is found to be associated with seasonal variations or presence of members of opposite sex.

All sense organ form an integral part of animal’s behaviour because the animal receives stimuli from external or internal environment thrugh sense organs. The brain coordinates all neural pheromonal and hormonal stimuli and brings out a specific pattern of behaviour. Thus behaviour and physiology are inseparable.

Credit:- Dr. Veer Bala Rastogi (KedarNathRamNath)

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