Abstract
BackgroundStereotypic behaviours, i.e. repetitive behaviours induced by frustration, repeated attempts to cope and/or brain dysfunction, are intriguing as they occur in a variety of domestic and captive species without any clear adaptive function. Among the different hypotheses, the coping hypothesis predicts that stereotypic behaviours provide a way for animals in unfavourable environmental conditions to adjust. As such, they are expected to have a lower physiological stress level (glucocorticoids) than non-stereotypic animals. Attempts to link stereotypic behaviours with glucocorticoids however have yielded contradictory results. Here we investigated correlates of oral and motor stereotypic behaviours and glucocorticoid levels in two large samples of domestic horses (NStudy1 = 55, NStudy2 = 58), kept in sub-optimal conditions (e.g. confinement, social isolation), and already known to experience poor welfare states. Each horse was observed in its box using focal sampling (study 1) and instantaneous scan sampling (study 2). Plasma samples (collected in study 1) but also non-invasive faecal samples (collected in both studies) were retrieved in order to assess cortisol levels.ResultsResults showed that 1) plasma cortisol and faecal cortisol metabolites concentrations did not differ between horses displaying stereotypic behaviours and non-stereotypic horses and 2) both oral and motor stereotypic behaviour levels did not predict plasma cortisol or faecal cortisol metabolites concentrations.ConclusionsCortisol measures, collected in two large samples of horses using both plasma sampling as well as faecal sampling (the latter method minimizing bias due to a non-invasive sampling procedure), therefore do not indicate that stereotypic horses cope better, at least in terms of adrenocortical activity.
Highlights
Stereotypic behaviours, i.e. repetitive behaviours induced by frustration, repeated attempts to cope and/or brain dysfunction, are intriguing as they occur in a variety of domestic and captive species without any clear adaptive function
Study 1 Stereotypic behaviours were observed in 65% of the horses in a total of 30 minutes of observation (9/12 horses in school 1, 18/26 in school 2 and 9/17 in school 3, chisquare test: X 2 2 = 1.82, P = 0.50) with a median frequency of 0.03 times per min (Q1 = 0.0, Q3 = 0.20, range: 0–0.8)
Here we investigated specific correlates of oral and motor stereotypic behaviours and glucocorticoid levels in two large and different samples of domestic horses, kept in sub-optimal conditions and already known to experience poor welfare states
Summary
Stereotypic behaviours, i.e. repetitive behaviours induced by frustration, repeated attempts to cope and/or brain dysfunction, are intriguing as they occur in a variety of domestic and captive species without any clear adaptive function. The coping hypothesis predicts that stereotypic behaviours provide a way for animals in unfavourable environmental conditions to adjust As such, they are expected to have a lower physiological stress level (glucocorticoids) than non-stereotypic animals. According to the coping hypothesis, individuals that display stereotypic behaviours are expected to have lower physiological stress levels (commonly assessed by measuring glucocorticoids concentrations) than non-stereotypic animals in the same sub-optimal environment. Pell and McGreevy [7], Clegg et al [8] and more recently Hemmann et al [9] report on the same species no significant differences in plasma and salivary cortisol levels between stereotypic and non-stereotypic horses (see [10] for similar results in pigs and [11] in margays Leopardus wiedii). McGreevy and Nicol [12] and Bachmann et al [13] report even higher basal plasma cortisol concentrations in adult stereotypic horses than in control non-stereotypic horses (see [14] for similar results in mink)
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