Environmentally enriching American mink (Neovison vison) increases lymphoid organ weight and skeletal symmetry, and reveals differences between two sub-types of stereotypic behaviour

• Published in: Applied animal behaviour science 2016-04, Vol.177, p.59-69
• Main Authors: Díez-León, María, Bursian, Steve, Galicia, David, Napolitano, Angelo, Palme, Rupert, Mason, Georgia
• Format: Article
• Language: English
• Subjects: American mink; Animal welfare; Carnivores; Corticosteroids; Enrichment; Fluctuating asymmetry; Immune system; Neovison vison; Stereotypic behaviour
• ISSN: 0168-1591; 1872-9045
• DOI: 10.1016/j.applanim.2015.12.002

•We examine long-term effects of preferred enrichment in American mink.•Enrichment reduced stereotypic behaviour and glucocorticoids.•Enriched mink showed signs of improved immunity and reduced developmental stress.•Within the same housing type, stereotypic behaviour and welfare did not covary.•Subtypes of stereotypic behaviour differ in sensitivity to current housing. Enrichment studies for wild carnivores (e.g., in zoos) are often short-term, use enrichments of unknown motivational significance, and focus on glucocorticoids and stereotypic behaviour (SB), ignoring other stress-relevant variables. Our study assessed the broad behavioural and physiological effects of enriching American mink—a model carnivore—with preferred stimuli long-term, and investigated the welfare implications of individual differences in SB. We raised 64 male-female pairs with or without enrichment. At 7 months, pairs were split and mink individually housed (adults being solitary), first by being temporarily moved to identical non-enriched cages (permitting observation blind to rearing condition). Two weeks later, one mink per original pair (half female, half male) was returned to his/her rearing cage for re-observation, sample collection for faecal cortisol metabolite (FCM) analysis, and additional research for 1.5 years before being humanely killed. Stress-sensitive variables were then measured post-mortem. Enriched-raised mink in their rearing conditions excreted less FCM (F1,29=8.33, p=0.003), and performed less SB than non-enriched mink. Two SB sub-types occurred: (1) ‘loco’ stereotypies: locomotor, whole body and head stereotypies (e.g., pacing, nodding), previously shown to correlate with recurrent perseveration; and (2) repetitive scrabbling with the forepaws. Enriched housing reduced both (at 7 months: loco stereotypies: F1,60=25.3, p