Stereotypic Behaviours are Heterogeneous in their Triggers and Treatments in the American Mink, Neo vison, a Model Carnivore
ABSTRACT: Stereotypic behaviours (SBs) are common in confined animals including captive Carnivora, which display diverse forms of SB: often whole-body movements (e.g. pacing), but also head-only movements (e.g. head twirling) and ‘scrabbling’ (scratching at enclosure boundaries). Although often pooled together, emerging evidence indicates that SBs are heterogeneous, suggesting that subtypes differ in their causes, triggers, and consequently treatments. In mink, a model carnivore, scrabbling seems to be elicited by neighbouring conspecifics. We tested this hypothesis via three studies of 32 males (individually caged in rows and separated by solid partitions). Study 1 investigated whether neighbour proximity affects the location of any SBs, and Study 2, whether removing neighbours reduces any SBs. Results revealed that although mink typically avoided proximity to their neighbours, scrabbling was uniquely directed towards neighbours who were close to the shared cage partition. It was also the only SB significantly elevated by having all-male neighbours, and reduced by removing neighbours. Study 3 then investigated whether environmental enrichment, a standard SB treatment. would reduce or abolish different SBs equally. To assess whether scrabbling is simply easier to alleviate than other SBs. Enrichment reduced all SB subtypes, but logistic regressions revealed that the odds of complete abolition were higher for whole-body and head-only SBs than for scrabbling. Overall, these naturally solitary carnivores thus seem to avoid conspecific proximity, but they specifically direct their stereotypic scrabbling at neighbours; and their scrabbling is reduced by neighbour removal, while their whole-body and head-only SBs are instead better alleviated with enrichment. Understanding that carnivore SBs are heterogeneous in their triggers and most effective treatments may help zoos, breeding centres and mink farms improve the design of their enclosures and the efficacy of their enrichments.