Factors influencing stereotypical behaviour patterns in horses a by kse10139

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									Factors influencing stereotypical behaviour patterns in horses: a review of 52 clinical cases
R.A.Casey
Anthrozoology Institute, University of Southampton, SO16 7PX, U.K. E-mail: Rachel.Casey@soton.ac.uk

Introduction Behaviours such as weaving, box-walking and wind-sucking have traditionally been regarded as
undesirable behaviours or ‘vices’ by horse owners, which has led to ‘treatment’ regimes that aimed to physically
prevent the performance of the behaviour rather than understand the underlying causes for it. In recent years, however, a
number of studies have shed light on the epidemiology of these behaviours (e.g. Luescher et al 1998), leading to the
development of more welfare compatible treatment options. In this study, a clinical population of horses presented with
stereotypical behaviours is examined for relationships between presenting signs and historical and observational
findings.
Materials and Methods The data for this study was collected from the case records of 52 clinical cases of equine
stereotypies referred to a veterinary behaviour specialist by first opinion veterinary surgeons in the South of England
between the years 1992 and 1998. Each horse was visited in its home environment for a behaviour consultation of
between two and four hours, prior to which each owner was sent a questionnaire which included details of the specific
problem behaviour, the signalment of the horse, the management system under which is was kept, and any information
that was available about the history of the horse. During the consultation the horse was observed displaying the
stereotypical behaviour where possible, or further information was obtained from owners as to the location, timing, and
specific triggers for the problem behaviour. The following variables were extracted from the case questionnaires and
reports: type of horse; age; sex; colour; purpose for which the horse was used; type of stereotypy; age of onset of
stereotypy; and triggering stimulus for stereotypical behaviour to occur. The population consisted of 19 Thoroughbreds
(TB)7 ‘Warmbloods’, 6 ‘Coldbloods’ 16 TB first crosses, and 4 Arabs or Anglo-Arabs. 26 of the horses were geldings,
5 entire males and 21 were mares, and the age range for the population was 4 to 17 years. 24 of the horses were kept as
general riding horses, 10 were used exclusively for dressage, 9 were used for eventing and / or show-jumping, and 7 for
racing or point-to-pointing. The relationship between the age of horses and other variables was examined using
Kruskal-Wallis tests. All other variables were compared using chi-square tests.
Results Of the 52 horses, 17 were weaving, 9 were crib-biters, 3 were windsucking, 9 were box-walking, 7 were head
nodding, 5 were displaying stereotypical lip or tongue movements (including wall or door licking), and 2 were self
mutilating. The self mutilating horses were excluded from further analysis because of the small number, and
windsucking and crib-biting horses were combined into a single category. No significant relationship was found
between type of stereotypy and sex, type of horse, purpose of horse, or colour. A significant relationship was found
between type of stereotypy and age of onset (χ2 = 38.142, df = 12, p<0.01), with a higher than expected count (40%) of
lip and tongue movement stereotypies starting between 1 and 3 years of age, and 50% of crib-biting and windsucking
starting at less than 1 year of age. Unfortunately, in the majority of cases (n = 37), age of onset of the behaviour was
unknown due to change of ownership. Age of onset was also related to the purpose for which the horse was kept, as
those used for racing / point-to-point were more likely to have an age of onset less than 1 year of age, and less likely to
have an unknown age of onset than those used for other purposes (df = 9, p = 0.01). This result needs to be viewed with
some caution, however, as the age of the horse at the time of the consultation may be a confounding factor. Horses in
the racing group were significantly younger at the time of consultation, and were hence less likely to have changed
hands than the older horses in the other groups. In fact, age at time of consultation was found to be significantly related
to age of onset (df = 3, p< 0.01). A significant relationship was found, however, between presenting stereotypy and the
factor identified as the primary trigger for the behaviour to occur (χ2 = 41.170, df = 8, p<0.01). Stimuli identified as
those responsible for triggering the stereotypy for each horse were simplified into 3 categories, which were:
(i)Anticipatory; behaviour occurs with human activities causing the horse excitement, anticipation or frustration, such
as preparing feeds, preparing to turn a horse out, tacking up for exercise, (ii)No stimuli; behaviour occurs in the
apparent absence of triggering stimuli in the stable or whilst at grass, and (iii) Conspecific; behaviour occurs in response
to activity of other horses, such as other horses passing the stable, or calling from out of visual contact. A higher than
expected count of weaving horses (71%) were primarily triggered to show this behaviour with anticipatory triggers.
Similarly, 92% of windsuckers did so with no apparent stimulus, and 56% of box-walkers displayed this behaviour with
conspecific activity. Precipitating factor was not related to type, age, sex or purpose.
Conclusion The results of this study suggest that the age of onset and triggering factors for stereotypical behaviour in
horses vary with physical presentation. The earlier age of onset for crib-biting and wind-sucking than for other
stereotypies is consistent with the findings of Waters et al. (2002) in their longitudinal study into the effect of weaning.
In addition, the relationship of stereotypy type and triggering factor supports the findings of other authors, such as
Cooper et al (2000) in the hypothesis that the origin of these behaviours are not uniform, and involve different
motivational states, stages of development and possibly different neuroanatomical and neurophysiological changes.
References
Cooper, J..J., McDonald, L, & Mills, D.S. (2000). The effect of increasing visual horizons on stereotypical weaving:
implications for the social housing of stabled horses. Applied Animal Behaviour Science, 69, 67-83.
Waters, A.J., Nicol, C.J. & French, N.P. (2002). The development of stereotypical and redirected behaviours in young
horses: the findings of a four year prospective epidemiological study. Equine Veterinary Journal
Luescher, U.A., McKeown, D.B. & Dean, H. (1998). A cross-sectional study on compulsive behaviour (stable vices) in
horses. Equine Veterinary Journal Suppl., 27, 14-18.
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