In this article we will discuss about the definition and approaches to ethology.
Definition of Ethology:
Man, from bygone days, had been interested in animal behaviour, for all animals (including himself) are involved in a variety of complex, vital relationships with members of their own species, with members of other species and with the physical environment.
Man’s survival, like that of animals, depends on its ability to procure food and shelter, to find mates and produce off-springs, and to avoid predation. Thus, the study of animal behaviour appears to have been fundamental to human existence as can be predicted from earliest cave paintings of animals.
The branch of biology that deals with the study of animal behaviour is called ethology. The word ethology is derived from the Greek word ethos, meaning “habit” or “character” and logos, meaning “study”. The term ethology was introduced by Niko Tinbergen (1950). Ethology is defined as the systematic and scientific study of the behaviour of animal (including human) under natural conditions.
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Genetics, developmental biology, anatomy, physiology, endocrinology, neurobiology, evolution, learning and social theory are all combined into one grand subject — animal behaviour. The field of ethology is, thus, integrative in the true sense of the word.
Approaches to Ethology:
The approach to ethology is based upon three foundations — the forces of natural selection, the ability of animals to learn and the power of transmitting learned information.
1. The Forces of Natural Selection:
According to Darwin any trait that causes its possessor to have some sort of reproductive advantages, would be favoured by the process, which he named as natural selection. Thus, natural selection is the process whereby traits that confer the highest relative reproductive success (greatest relative fitness) on their bearers and which can be passed down across generations, increases in frequency over many generations.
To elaborate how natural selection operates in the wild, let us take the example of beak size in Galapagos finches, which is also called Darwin’s finches. Two such finch species’, Geospiza magnirostris and G. fortis, beak size can be utilised to elaborate the role of natural selection in animal behaviour.
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The bigger of the two species is G. magnirostris, which has relatively large beak. It can crack open large and very tough fruit of the caltrop (Tribulus cistoides) much more quickly and efficiently than the smaller finch, G. fortis.
On the other hand, G. fortis is more efficient when it comes to small seeds. Thus, natural selection would favour larger beaked birds in times when caltrops and other large seeded plants are abundant and smaller beaked birds would be favoured when smaller seeded plants are plentiful.
Such a prediction would hold true with respect to both a comparison between these two species, as well as within each species. Thus, not only should G. magnirostris would be favoured over G. fortis when large seeds are abundant, but also larger G. magnirostris would be favoured over smaller G. magnirostris and, similarly, larger G. fortis over smaller G. fortis.
2. Individual Learning:
Animals in course of their lifetime learn about everything from food and shelter to predators and familial relationships. Such individual learning represents a second major force and can alter the frequency of behaviour within the lifetime of an organism.
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Individual learning can take many forms. Considering the hypothetical case of learning in the context of mating, it has been observed that females of most animals mate with numerous males throughout the course of a lifetime. For example, imagine a female bird mating with various males somehow able to keep track of how many chicks fledged their nest (1, 2, 3 and so on).
Such a female might learn which male is a good mate by keeping track of the number of eggs she laid when associated with each male (Fig. 5.1). As more egg laying is the preference, during later mating opportunities, such female birds would be likely to choose male bird 2 as she has learned that she lays the most eggs (four as shown in Fig. 5.1) after mating with him. In such a case, learning has changed the behaviour of an animal within the course of a life time.
The above is a good example of how learning and natural selection can be intimately tied together. In this example, females change their preference for mates as a result of prior experience and, therefore, learning affected behaviour pattern within a generation.
Such behaviour based on personal experience can not only shift mate choices within a generation, but it can also change the ability to learn, which if genetically coded, can be subjected to natural selection. Natural selection might very well favour the ability to learn about mates, over the lack of such an ability.
3. Cultural Transmission:
This is considered to be the third major force affecting animal behaviour, where animals learn something by copying the behaviour of others, through what is known as social learning. Cultural transmission can allow newly acquired traits to spread through populations at a very quick rate, as well as permit the transmission of information across generations rapidly.
The importance of cultural transmission and social learning in animals can be exemplified in the case of foraging in rats. Rats, being scavengers, are often presented with opportunities to sample new food. On one hand, a new food source may be an unexpected rat bounty, while, on the other hand, new foods may be dangerous, because either they contain elements inherently bad for rats, or the rats do not know how a new food should smell.
So the rats face the difficulty to tell whether this new food is fresh or spoiled. To overcome this, foragers often learn critical tidbits about the location and identity of food by interacting with others who have recently returned from a foraging bout.
In case of individual learning, it is certainly possible that if the above behaviour of “copy the diet choice of others” is genetically coded, then the rule might increase in frequency through natural selection. The case of cultural transmission, on the other hand, is more complicated than that of individual learning. The reason being that what an animal learns via individual learning is lost when the animal dies.
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The actual information that one learns via individual learning never makes it across generations. However, this is not the case with cultural transmission, where what a single animal does, if copied, can affect individuals many generations later on. Cultural transmission, thus, has both within- and between-generation effects.
Conceptual-Theoretical-Empirical Approaches in Ethology:
Studies in animal behaviour tend to use all these three approaches:
In conceptual approaches, ideas generated in different sub-disciplines are imported and combined in a new, cohesive way. Major conceptual advances tend to generate not only new experimental work, but they also reshape the way that a discipline looks at itself.
In many species, like the vervet monkey (Cercopithecus aethiops), exhibits kin selection and mother-offspring bond, where mothers go to extreme lengths to provide for and protect their young offsprings.
This provides a conceptual framework for understanding the special relations that blood relatives share. Individual’s total fitness, measured by its genetic contribution to the next generation, is not simply a function of the number of viable offsprings that it produces—rather, it is a combination of the number of young it raises, plus some benefit assigned for any help it provided in raising the offspring of blood relatives.
Theoretical approach:
Theoretical approach to animal behaviour relates to the construction of a mathematical model. A question of interest is: If a list of potential edible items is given, which one should a foraging animal add to its diet and under what conditions? Ethologists have constructed mathematical models of foraging that determine which potential prey items should be taken.
The value assigned to each prey is a composite of energy value (e), handling time (h), and encounter rate (λ) associated with various items to predict which such item should be added to an animal’s diet to optimize some quantity, such as energy intake per unit time.
For example, the model predicted that whether or not a low-ranked food item would be added to an animal’s diet depended on the availability of the low-ranked item itself. Such as, if for wolf predators, rabbit provided more energy per unit time than did chickens, then the availability of rabbits, not chickens, would determine whether chickens would be added to the wolf’s diet.
Empirical studies are designed to test the theories and concepts that have been proposed as explanations for behaviour. Of the many forms the most essential empirical work in ethology is either observational or experimental.
Observational work requires watching and recording of what animals do, but no attempt is made to manipulate or control an ethological or environmental variable. For example, one might go out into a forest and record every action of a particular flock of birds.
In doing so, he would note various behaviours like foraging, encounter with predators, feeding of nestlings, the time and duration it sits on a particular tree, and so on. From such work, one can visualize-
1. The time budget of the birds in study.
2. The foraging of the males and females.
3. Predict their relation of foraging bouts when predators are present in their vicinity.
4. Find the correlation between foraging behaviour and predation pressure, and so on.
However, from the above observational work, it is difficult to speak of what caused what. It may be that there are other variables which might be responsible for the correlation of foraging with predation pressure. To know that, one might have to experimentally manipulate the system.
For example, two areas might be taken. In area 1 the predators may be increased, while in area 2 natural conditions may prevail. Now it is to be seen whether foraging is affected by the increase in predators or not. Therefore, we can then confidently conclude whether increased predation pressure causes decreased foraging activity or not.