Behaviour; a way to survive.
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Introduction
In discussing the behaviour of animals, it is wise for students to keep the BIG PICTURE clearly in view. The three statements which follow are fundamental to that big picture.
In discussing the value of any type of behaviour, students should remember that behaviours which ensure the survival of individuals to reproductive maturity are likely to be advantageous. Such behaviours are likely to
- conserve energy
- locate and defend food sources
- help the group maintain social structure
- attract a mate
- ensure that some offspring survive
- ensure the survival of the species.
"In this area of study survival of a species should be considered as the sum of the survival of individuals of that species. The frequently used term 'survival of the fittest' is best applied to individuals (or their individual alleles) and follows logically from the concepts of survival in an environmental context."
VCE Study Design. p24 © Board of Studies, used with permission.
In discussing the behaviour of animals other than humans, students must take care to avoid the use of anthropomorphic arguments. That is, animals other than humans probably to do NOT think, reason, or have feelings as do humans, and it is wrong to ascribe such human motives to animals for their behaviour.
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Adaptations and behaviour - definitions.
Adaptations are particular characteristics of the members of a species which help that species to survive in its particular environment. Adaptations are usually classified as structural (a result of particular anatomical features), functional (a result of the organisms' metabolic capacities and tolerance limits - physiology) or behavioural (the things the members of the species can do in response to stimuli).
Behaviour is the complex, coordinated set of responses of an individual or a group of individuals in response to stimuli.
The stimulus that initiates a particular behaviour may be external or internal.
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Innate and learned behaviour.
The ability to behave appropriately may be programmed into an organism in its genes (innate), in which case the organism will carry out that behaviour without any need to observe other members of the species doing it.
Alternatively, an individual may only demonstrate a particular behaviour after finding out by experience that the behaviour is beneficial (learning). There are several different methods of learning. However, if an animal does not have the necessary physiological and anatomical features to carry out a particular behaviour, then no amount of learning will make it possible.
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Structure and function in determining behaviour.
Physiology (how an animal functions) influences behaviour in a variety of ways. Physiology is essentially the internal stimulus that triggers a number of behavioural responses. For example, temperature and pain receptors may initiate a particular response, low blood nutrient concentrations might initiate a different response and elevated blood sex hormone concentrations would be expected to trigger another entirely different response.
Structures have evolved along with behaviours that make the most of the activities the structures permit. Sometimes the behaviours associated with particular structures are obvious, for example wings and flight, sometimes they are less clear - are giraffes' legs long for increased speed or increased height? If a structure ceases to be of use to a species, it is sometimes, but not always, lost over many generations. The genetic information for a structure that confers a survival advantage is unlikely to be lost in a species.
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Solitary or group behaviours in relation to the animal's habitat.
Solitary behaviours are those carried out by a lone animal. The animal may or may not be a part of a larger aggregate of animals of the same or (less likely) different species. Animals are most likely to engage in solitary behaviour when competition from other individuals would be a disadvantage. For example, the Asian panda spends most of its adult life alone, presumably because it requires huge amounts of bamboo to meet its energy requirements, and 'sharing' a habitat with another panda would disadvantage them both.
Group behaviours are frequently complex, they have usually evolved in habitats where isolated individuals would be unlikely to survive. Groups of animals usually organise themselves into hierarchies, where different individuals have different roles to play. It is in these hierarchies that order is maintained by the dominant individuals, who often claim mating rites. Other individuals may have defined behaviours such as hunting for food or protection of the group. Examples of such dominance heirarchies are chickens in a farm-yard (from whence the term 'pecking order' - the dominant bird/s eat first) or kangaroos in a mob in the Australian bush.
In these complex social structures the survival chance of the species is enhanced, although many individuals may not survive to reproduce themselves.
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Complex communication systems involving a range of senses.
Communication systems are any sequences of stimuli initiated in one organism that may elicit a response in an individual of the same or different species.
Communication may be used for a number of purposes; warning of danger, informing about location of food, attracting a mate, claiming a territory and others. Within a species, different signals mean different things, so whilst we humans might not understand the communications between animals, they are important for the survival of the animal species.
Senses used in communication
The senses used in communication vary. All five senses: sight, smell, sound, taste and touch are used in various ways by various animals.
See if you can think of at least two (non-human) examples of animals' communication methods that illustrate communication by each of the five senses.
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Territorial behaviours in the defence of feeding or nesting sites.
Territorial behaviour involves an individual or individuals of a group defending an area, usually of fixed boundaries, from other members of , usually, the same species.
This defence may include communication through smell (eg urine or pheromone marking), sight (eg displays of fierce looking anatomy), sound (eg growling), or usually as a last resort, by fighting.
The object of such behaviour is to retain a suitable habitat for survival of that individual or group of individuals. Such survival relies on the maintenance of feeding sites and nesting sites, without which individuals would not reach reproductive maturity and ensure that the species genes are passed on to the next generation.
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Aggressive and submissive behaviours.
Aggressive behaviour is most likely to be observed in groups where a dominance hierarchy exists. Aggression, as the behaviours described for territoriality, may take many forms, with fighting usually the behaviour of last resort. The purpose of aggression is to maintain or challenge the dominance relationships within a group. Aggression rarely leads to the death of the 'loser', to remove genes by killing members of the species is counterproductive.
Submissive behaviour is the behaviour exhibited in response to displays of aggression. It shows deference to the more dominant member(s) of the group, either following a period of fighting or as a means of avoiding a fight.
Together, aggressive and submissive behaviours can lead to complex relationships within groups of animals, sometimes known as a pecking order or dominance heirarchy.
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Reproductive behaviours including courtship and parental care.
Reproductive behaviour is the total range of behaviours that combine to ensure that sexually mature individuals meet, mate and leave enough viable offspring to continue the species. In some species (eg oysters), the only behaviour required to ensure the survival of the species is the coordinated release of gametes into a suitable environment. In other species (eg seagulls), a complex series of behaviours has been observed leading up to and following mating.
Courtship behaviour can be quite spectacular as partners try to attract the attention of a suitable mate: nest building, plumage ruffling, elaborate displays of anatomical features, and emission of irresistible scents are some of the methods employed. (Does this sound like some people you have observed at parties?!)
Parental care is not practiced by all species. In many cases, huge numbers of offspring are born (eg thousands of fish eggs are laid and hatch), and the sheer numbers mean that at least a few individuals will survive to reproductive maturity. In other species, however, the parents protect the unborn young (eg birds, mammals), and feed and protect the young until they are capable of independent existence. In general, the fewer offspring a species has per mating, the longer the parental care period. This, therefore, increases the survival chances of a species with a naturally low birth rate.
Make sure that you do plenty of case study questions as part of your study of this section.
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This page is maintained by Jenny Herington, who can be contacted at bio_cat@bioserve.latrobe.edu.au by email.
All of the pages at the VCE Biology Students' site are copyright © Biochemistry, LaTrobe University.
Last update :24 March 97
