WHO NEEDS BEHAVIORAL NEEDS - MOTIVATIONAL ASPECTS OF THE NEEDS OF ANIMALS

The aim of this paper is to investigate the question of whether there exist needs to perform particular behaviours when the physiological needs of the animal are taken care of. According to current theory, there exist apparent behavioural needs to perform parts of the behavioural repertoires of animals, fulfilling some or all of the following three criteria: (1) the behaviour patterns are mainly caused by internal factors; (2) the tendencies are gradually built up while they are not being performed; (3) the mere performance of the behaviour patterns is rewarding. This has led to a 'catalogue approach', where welfare theorists have attempted to divide the behavioural repertoire of different species into those whose expression constitute needs and those that do not. We dispute this simplistic view. In light of the data we review, we argue that it is conceptually wrong to dichotomize and rank the motivational effects of external and internal factors. Motivation is inextricably a function of both, although the variation in behavioural output may, in a given situation, be explained by the variation in either. In some cases, the tendency to perform a behaviour does rise as a function of time. This may be caused by factors associated with tissue needs or factors intrinsic to the nervous system, or both. However, we see no reason for why a behavioural expression should be a need if its tendency builds up with time and not so if other motivational processes are responsible for its variation. We also argue that although species-specific motor activity sometimes might appear to be reinforcing to an animal, this is, in most cases, difficult to ascertain. Moreover, a need may be present even if the behaviour is not self-rewarding. In assessing the needs of animals we argue for a holistic approach to the motivational control of behaviour. Rather than focusing on one aspect, e.g. whether the behaviour is caused by external or internal factors, we suggest that the total behavioural system is analyzed. When considering even rather simple and well-defined behaviour, like nest building of domestic sows (Sus scrofa) and dust-bathing of domestic hens (Gallus gallus), such a complicated picture emerges, that we regard it as impossible to denote the performance of some behaviour patterns of a species as 'needs' as opposed to other elements of the repertoire. We reject the 'catalogue approach', but not the idea that there are needs which are best described as ethological; in the sense that preventing an animal from carrying out a certain behaviour in a given situation might cause signs of suffering. There are probably needs associated with the performance of all species-specific behaviour and those are a complex of obtaining a goal and performing the motor patterns. Whether one wants to describe behaviour as a need therefore depends on a knowledge of the environmental context. Thus, a behaviour may be a called need in a particular situation.