What Questions Do Biologists Ask About Behaviour?
Ethology: the study of animal behaviour from an evolutionary perspective
For many animals, much of their behaviour is like the web-spinning behaviour of spiders –unlearned and highly
Stereotypic behaviour is often species-specific – most individual of a given species perform the behaviour in the same
How Do Genes and Environment Interact to Shape Behaviour?
Genes do not encode behaviours, rather affect behaviour by setting motion a series of gene-environment interactions
that underlie the development of proximate mechanisms that enable certain behavioural responses.
Experiments can distinguish between genetic and environmental influences on behaviour
Deprivation experiment: rear young animal so it is deprived of all experiences relevant to the behaviour understudy. If it
still exhibits the behaviour, we may assume that the behaviour can develop without opportunities to learn it.
Genetic experiment: investigators alter the genomes of organisms by interbreeding closely related species, by
comparing individuals that differ in only one or a few genes or by knocking out or inserting specific genes to determine
how these manipulations affect their behaviour.
Genetic control of behaviour is adaptive under many conditions
Individuals might fail to acquire the appropriate behaviour, or acquire the appropriate behaviour, or acquire
inappropriate behaviour, if genes did not exert strong influences on the development of the behaviour.
Inherited behaviour is also adaptive when mistakes are costly or dangerous.
Inheritance of behaviour patterns used to avoid predators or capture dangerous prey is obviously adaptive; allow no
room for mistakes.
Releaser—an object, event, or condition required to elicit behaviour.
Imprinting takes place at a specific point in development
Some types of learning take place only at a specific time in animal’s development critical period.
Imprinting –animal learns a set of stimuli during a limited critical period (e.g. behaviour learned by imprinting is the
recognition of offspring by their parents and of parents by their offspring).
Individual recognition must often be learned quickly; opportunity to do so may arise only once.
Imprinting requires only a brief exposure, but its effects are strong and can last a long time.
The critical period for imprinting may be determined by a brief development of hormonal state.
Hormones influence behaviour at genetically determined times
In multicellular organisms, all behaviour depends on the nervous system for initiation, coordination, and execution.
Hormones of the endocrine system determine when a particular behaviour is performed, as well as when certain
behaviours can be learned.
How Do Behavioural Responses to the Environment Influence Fitness?
Choosing where to live influences survival and reproductive success
Environment in which an organism lives is called its habitats.
Cues most organisms use to select suitable habitats have a common feature: they are good predictors of conditions
suitable for future survival and reproduction.
Visual information can also provide useful cues about the quality of a habitat. Many animals use the presence of already
settled individuals as an indication that the habitat may be good.
Some highly social animals actually “vote” on the quality of habitats.
Defending a territory has benefits and costs
When high-quality habitats are in limited supply, animals may compete for access to them.
An animal may improve its fitness by establishing exclusive use of its chosen habitat
Most common way is by establishing a territory from which in excludes conspecifics (same species) and sometimes
those of other species as well by advertising that it owns the area or by chasing others away; but this takes a lot of
energy which could have been used for beneficial purposes.
Cost-benefit approach assumes that an animal has only a limited amount of time and energy to devote to its activities.
Animals cannot long perform behaviours whose total costs are greater than the sum of their benefits.
The benefits of behaviour are the improvements in survival and reproductive success. The total cost of any behaviour
typically has three components:
o Energetic cost: difference between the energy the animal would have expended had it rested and the energy
expended in performing the behaviour. o Risk cost: increased chance of being injured or killed as a result of performing the behaviour, compared