Many captive animals perform repetitive, relatively invariant and apparently functionless behaviours - commonly known as stereotypies (e.g. [1]). The underlying causes of this type of behaviour are unclear, but they may be indicative of poor welfare. Although much research has been carried out in this area, many unanswered questions remain. This study forms a preliminary investigation into the motivation behind behaviour that is without apparent function, using laboratory mice as a model species. A practical advantage of working with a species such as the mouse, with its relatively high developmental rate, is that the onset of stereotypy and its development could be monitored over a reasonably short time span. In addition, previous work has shown that laboratory mice will readily perform stereotypic behaviour (e.g. [2]). The aim of this initial investigation was to establish simple methodologies for sampling the behaviour of laboratory mice in order to objectively and efficiently quantify the incidence of stereotypies. The long-term aim was to use these sampling techniques to identify individual variation in stereotypy for use in developmental studies into the causes and effects of stereotypy as they relate to the welfare of captive animals.

General behaviour patterns were monitored in a population of 16 laboratory mice comprising both sexes and two outbred strains (CD-1 and NIH/S), covering their developmental period from weaning to maturity. These strains of mice are prevalent in experimental research, thus affording the study direct relevance to experimental animals. Observations were carried out over five months with video recordings at approximately monthly intervals. A combination of time lapse and real time footage was obtained, comprising in total, 70 hours of time lapse and 24 hours of real time footage per mouse. Of this, behavioural data were collected from 14 hours of time lapse video per mouse through scan sampling; and 12 hours of real time video per mouse through continuous sampling using The Observer 3.0 (Noldus Information Technology). Preliminary filming sessions monitored the animals' behaviour in standard laboratory conditions with sawdust bedding and ad libitum access to food and water. Having collected baseline data, the cages of half the subjects were modified through the addition of a nesting substrate in order to determine whether this environmental modification gave rise to changes in behaviour. Statistical analyses (using data generated by The Observer elementary statistics function) focused on the frequency and duration of behaviour directed towards the cage lid that may be regarded as stereotypic. Lid-directed behaviour comprised five mutually exclusive categories with quantifiable properties. Results obtained to date indicate that the frequency and total duration of observed cage lid-directed behaviour was significantly greater in the CD-1 strain at six and eleven weeks of age (p<0.05). Environmental, gender and age comparisons, however, showed no significant differences in these measures, though individual differences in lid-directed behaviour was stable over time.

References

1. Mason, G.J. (1991) Stereotypies: a critical review. Animal Behaviour, 41, 1015-1037.
2. Würbel, H.; Stauffacher, M.; von Holst, D. (1996) Stereotypies in laboratory mice - quantitative and qualitative description of the ontogeny of 'wire-gnawing' and 'jumping' in ICR and ICR nu-mice. Ethology, 102, 371-385.

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