María Díez-León

Recurrent perseveration correlates with abnormal repetitive locomotion in adult mink but is not reduced by environmental enrichment

We analysed the relationship between abnormal repetitive behaviour (ARB), the presence/absence of environmental enrichment, and two types of behavioural disinhibition in farmed American mink, Neovison vison. The first type, recurrent perseveration, the inappropriate repetition of already completed responses, was assessed using three indices of excessive response repetition and patterning in a bias-corrected serial two-choice guessing task. The second type, disinhibition of prepotent responses to reward cues, a form of impulsivity, was tested in a locomotive detour task adapted from primate reaching tasks: subjects were required to walk around, rather than directly into, a transparent barrier behind which food was visible. In older adult females, recurrent perseveration positively predicted pre-feeding abnormal repetitive locomotion (ARL) in Non-enriched housing. High-ARL subjects also performed repeated (same-choice) responses more rapidly than low-ARL animals, even when statistically controlling for alternated (different-choice) response latency. Mink performed much less ARL following transfer to Enriched housing, but there was no corresponding change in recurrent perseveration. Thus, elevated recurrent perseveration is not sufficient for frequent ARL; and while captive environments do determine ARL frequency, in mink, they do not necessarily do so by modifying levels of perseveration. Disinhibition of prepotent responses to reward cues, meanwhile, did not predict ARL. In a separate sample of differentially housed young adults, neither type of behavioural disinhibition predicted ARL, and again, whether or not housing was enriched did not affect behavioural disinhibition despite affecting ARL. Thus, the relationship between recurrent perseveration and ARB may only develop with age; longitudinal studies are now required for confirmation.

Benefits of a Ball and Chain: Simple Environmental Enrichments Improve Welfare and Reproductive Success in Farmed American Mink (Neovison vison)

Can simple enrichments enhance caged mink welfare? Pilot data from 756 sub-adults spanning three colour-types (strains) identified potentially practical enrichments, and suggested beneficial effects on temperament and fur-chewing. Our main experiment started with 2032 Black mink on three farms: from each of 508 families, one juvenile male-female pair was enriched (E) with two balls and a hanging plastic chain or length of hose, while a second pair was left as a non-enriched (NE) control. At 8 months, more than half the subjects were killed for pelts, and 302 new females were recruited (half enriched: ‘late E’). Several signs of improved welfare or productivity emerged. Access to enrichment increased play in juveniles. E mink were calmer (less aggressive in temperament tests; quieter when handled; less fearful, if male), and less likely to fur-chew, although other stereotypic behaviours were not reduced. On one farm, E females had lower cortisol (inferred from faecal metabolites). E males tended to copulate for longer. E females also weaned more offspring: about 10% more juveniles per E female, primarily caused by reduced rates of barrenness (‘late E’ females also giving birth to bigger litters on one farm), effects that our data cautiously suggest were partly mediated by reduced inactivity and changes in temperament. Pelt quality seemed unaffected, but E animals had cleaner cages. In a subsidiary side-study using 368 mink of a second colour-type (‘Demis’), similar temperament effects emerged, and while E did not reduce fur-chewing or improve reproductive success in this colour-type, E animals were judged to have better pelts. Overall, simple enrichments were thus beneficial. These findings should encourage welfare improvements on fur farms (which house 60-70 million mink p.a.) and in breeding centres where endangered mustelids (e.g. black-footed ferrets) often reproduce poorly. They should also stimulate future research into more effective practical enrichments.

Setting priorities for existing conservation needs of crayfish and mink

According to Clavero (2014), the conservation in Spain of the white-clawed crayfish (Austropotamobius italicus) and the European mink (Mustela lutreola) to the detriment of 3 North American species (red swamp crayfish [Procambarus clarkii], signal crayfish [Pacifastacus leniusculus], and feral American mink [Neovison vison]) represents a case of shifting baseline syndrome (Pauly 1995; Papworth et al. 2009). Clavero argues there is clear evidence that all these species are nonnative to the Iberian Peninsula and therefore preserving the white-clawed crayfish and the European mink responds to an a priori social assimilation of these species as native and, thus, to a shift of the baseline of Spanish natural freshwater ecosystems. We question Clavero’s evidence on the nonnative status of these 2 species in the Iberian Peninsula and disagree with the importance he attributes to species’ native or nonnative status when setting conservation priorities. Nonnative species occur outside their historical natural range following intentional or accidental human introduction (Heywood 1995). Contrary to Clavero’s claim, evidence suggests the white-clawed crayfish and the European mink are native to the Iberian Peninsula (see below). Moreover, the current known European distribution for both species makes natural dispersion a plausible biogeographic process because the Pyrenean range is permeable at its extremes (e.g., Mart́ınezRica & Monserrat-Recoder 1990) and, at least for mustelids, mountains are not a barrier to dispersal (e.g., Zuberogoitia & Zabala 2003).

Effects of environmental enrichment and stereotypic behavior on maternal behavior and infant viability in a model carnivore, the American mink (Neovison vison).

In several species, stress compromises maternal behaviors that are important for infant viability (e.g. licking and grooming). Understanding how stress in captivity affects maternal behavior could therefore be beneficial, especially for carnivores in zoos and breeding centers where infant mortality is often high. We used a model carnivore--American mink--to test two hypotheses, namely that maternal investment and/or behavior is i. improved by environmental enrichment; and ii. compromised by stereotypic behavior. We observed 22 females raised in an indoor facility, 9 enriched, 13 non-enriched. At birth, and at post-natal day 20 when altricial infants were still fully dependent on their mothers, the following offspring variables were recorded: litter size, infant mortality, litter sex ratio (post-natal day 1), and weight. Maternal behavior was assessed by recording nest shape (post-natal day 1), and the frequency of licking and grooming (post-natal days 1-7). Non-enriched females stereotyped more, had female-skewed litters at birth, and tended to make poorer, flatter nests. Maternal licking and grooming showed large, stable individual differences, but appeared unaffected by enrichment. High levels of maternal stereotypic behavior predicted slower offspring growth, replicating previous findings for farmed mink. Nevertheless, enrichment did not significantly increase infant growth rates nor decrease infant mortality. Due to small sample sizes, our study now needs replicating, particularly to explore the potential benefits of enrichment on nest building, sex ratio effects, and the implications of maternal licking and grooming for offspring stress reactivity. Findings could then apply to endangered mustelids like the European mink.

Simple year-round cage enrichments for mink

Subjects were 2,400 kits from 600 families, on 3 commercial farms in Ontario, pair-housed from July-December. 75% were Blacks, 25% Demis. Two male-female pairs were used per family: one was provided with stimuli for interaction; the other housed in standard conditions. The supplemented cages received a golf ball, plastic wiffle ball, and hanging device to tug /chew (hose or plastic chain) (costing under

Environmentally Enriched Male Mink Gain More Copulations than Stereotypic, Barren-Reared Competitors

1.50 a cage). Behaviour, temperament, mortality rates and pelt quality were assessed. Supplemented kits were found to play more than their non-enriched siblings. Social play (defined as ‘rough and tumble’ interactions without screaming or hard biting) was unaffected, but enhanced object and locomotor play led to significantly higher overall levels in supplemented juveniles. There was no evidence that the added objects increased aggression. The added objects also had no effects on mortality. In stick tests in December, supplemented mink were significantly less likely to be fearful than their standard-housed siblings. When scored for reactions to the live-grading of their fur in November, supplemented mink were significantly less likely to scream than their standard-housed siblings. Across Blacks, the added objects did not seem to affect fur quality, but in Demis, supplemented mink were significantly likely to receive better live-grades than their standard-housed siblings. For pelted subjects, tails of dead animals were inspected for signs of tail-chewing/clipping. Typically 1 cm or less of the tailtip was affected. However, 20 mink across all three farms showed damage to 2 cm or more the tail, and 14 of these were standard-housed rather than supplemented: a trend to significance. Furthermore, pooling all instances of tail-chewing/-biting together, 7.9% supplemented mink had sucked/bitten tails, compared to 11.5 standard-housed: a significant effect. The pelts of all experimental mink were bar-coded for auction, and prices will be obtained in summer 2012. Data during mating showed that supplemented males were more effective maters than standard mink (e.g. showing longer copulations). Subjects selected for breeding have also been evaluated for stereotypic behaviour and faecal cortisol metabolite output, and for whelping success: data still to be analysed. Overall, these findings to date show that simple, long-term, cheap additions to standard cages can act as effective environmental enrichments for farmed mink.