title: Environmentally enriched male mink gain more copulations than stereotypic, barren-reared competitors.
abstract: Wild carnivores in zoos, conservation breeding centres, and farms commonly live in relatively small, unstimulating enclosures. Under these captive conditions, in a range of species including giant pandas, black-footed ferrets, and European mink, male reproductive abilities are often poor. Such problems have long been hypothesized to be caused by these animals' housing conditions. We show for the first time that rearing under welfare-improving (i.e., highly valued and stress-reducing) environmental enrichments enhances male carnivores' copulatory performance: in mate choice competitions, enriched male American mink (Neovison vison) mated more often than non-enriched males. We screened for several potential mediators of this effect. First was physiological stress and its impact on reproductive physiology; second, stress-mediated changes in morphology and variables related to immunocompetence that could influence male attractiveness; and third, behavioural changes likely to affect social competence, particularly autistic-like excessive routine and repetition ('perseveration') as is reflected in the stereotypies common in captive animals. Consistent with physiological stress, excreted steroid metabolites revealed that non-enriched males had higher cortisol levels and lower androgen levels than enriched conspecifics. Their os penises (bacula) also tended to be less developed. Consistent with reduced attractiveness, non-enriched males were lighter, with comparatively small spleens and a trend to greater fluctuating asymmetry. Consistent with impaired social competence, non-enriched males performed more stereotypic behaviour (e.g., pacing) in their home cages. Of all these effects, the only significant predictor of copulation number was stereotypy (a trend suggesting that low bodyweights may also be influential): highly stereotypic males gained the fewest copulations. The neurophysiological changes underlying stereotypy thus handicap males sexually. We hypothesise that such males are abnormally perseverative when interacting with females. Investigating similar problems in other taxa would be worthwhile, since many vertebrates, wild and domestic, live in conditions that cause stereotypic behaviour and/or impair neurological development.
authors.affiliation: Department of Animal and Poultry Science, University of Guelph, Guelph, Ontario, Canada.
authors.forename: María
authors.initials: M
authors.lastname: Díez-León
authors.forename: Jeff
authors.initials: J
authors.lastname: Bowman
authors.forename: Steve
authors.initials: S
authors.lastname: Bursian
authors.forename: Hélène
authors.initials: H
authors.lastname: Filion
authors.forename: David
authors.initials: D
authors.lastname: Galicia
authors.forename: Jeannette
authors.initials: J
authors.lastname: Kanefsky
authors.forename: Angelo
authors.initials: A
authors.lastname: Napolitano
authors.forename: Rupert
authors.initials: R
authors.lastname: Palme
authors.forename: Albrecht
authors.initials: A
authors.lastname: Schulte-Hostedde
authors.forename: Kim
authors.initials: K
authors.lastname: Scribner
authors.forename: Georgia
authors.initials: G
authors.lastname: Mason
mesh_terms: D000818:Animals; D003307:Copulation; D005260:Female; D008297:Male; D008907:Mink / Q000502:physiology*; D011247:Pregnancy; D012726:Sexual Behavior, Animal; D013239:Stereotyped Behavior