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An Introduction to Animal Behaviour and Sociobiology

Tinbergen’s four Questions of Ethology

Explanations to Tinbergen’s questions can be split into two groups; evolutionary (ultimate) and proximate. Ultimate explanations pertain to the evolution of a species and include:

Function (adaptation) – This type of explanation for animal behaviour usually concerns a trait that is functional to the reproductive success of the organism which is a result of natural selection. Why an organism is the way it is

Evolution (phylogeny) – This type of explanation for animal behaviour encapsulates all evolutionary explanations other than function/adaptation, it include the history of the species reconstructed from as far back as possible. Sequential changes in a species through time

Proximate explanations pertain to individuals within the species and include:

Mechanism (causation) – This type of explanation describes an organism’s structure and how biological mechanisms of the organism are able to work. What organism’s structures are like and how they work

Development (ontogeny) – This type of explanation describes how an organism has developed, from changes in its DNA code to the different forms of life stages. Sequential changes in individuals across their lifespan

Examples of Explaining Tinbergen’s four Questions of Ethology

Example 1: Why do birds sing in spring?

• Mechanism – Alterations in day length affect hormone secretions within birds

• Function – Singing helps to defend the bird’s territory as well as attract females

• Evolution – Here you would need to compare the songs of a species of bird throughout the species’ evolution

• Development – This concerns the learning of an individual bird’s song, which would be easier to observe than the evolution aspect above

Example 2: Why do we see?

• Mechanism – The lens of the eye focuses light on the retina visual system

• Function – We see so we can find food easier and avoid danger

• Evolution – The vertebrate eye initially developed with a blind spot, the lack of adaptive intermediate forms prevented the loss of this blind spot

• Development – Neurons connect the eye to the brain and require photo-stimulation to transmit information

Example 3: Why do we not find siblings attractive? (Westermarck effect)

• Mechanism – Little is known about this neuromechanism

• Function – To discourage inbreeding which would otherwise decrease the number of viable offspring

• Evolution – This mechanism is found in a number of mammalian species which suggests it may have evolved tens of millions of years ago

• Development – Results from familiarity with another individual early in life, especially in the first 30 months for humans. The effect is also manifested in nonrelatives raised together

The Comparative Method

In ethology, comparative is used in specific sense, meaning to indicate systematic comparisons between different species (including humans). The comparative method has been used by Lorenz to make inferences about the evolution of behaviour and by Gittleman to study evolutionary function.

One way of using the comparative method to make comparisons about species is to gather information on two variables which are believed to be related. Collect data from each species and plot this on a graph. If the variables are related, there will be a positive linear relationship and the differences between species can be compared. For example, body weight against testes weight gives a positive linear relationship.

The outcome of the method becomes useful when groups are made within the data, using the testes example, by forming groups of species which are either monogamous, have one dominant male or have multiple males we can compare relative testes weights. We can see that on average multi-male species have larger testes, whilst monogamous species have smaller.