The chewing of plastic drinker dishes has also been observed on at least two farms. It appears to be infrequent, but also quite prevalent across individuals. Nest-boxbiting and wire mesh licking have also been observed, though, again, infrequently, the latter authors classifying it as a stereotypy. Again, the welfare significance of such behaviour is unknown. &RQFOXVLRQV 1. The responses of mink to stressors and environmental manipulations are reasonably well understood but there is much fundamental work still to be done. A wide range of behavioural and physiological indices have been investigated, and furthermore, mink studies can readily involve SRVW PRUWHP measures, as onsite slaughter facilitates autopsy. 2. Body weight, hypothalamo-pituitary-adrenal activity, heart rate, eosinophil levels, gastric ulceration, willingness to mate, infertility, litter mortality, playing, vocalisations, staying within the nest box, showing fear of humans, stereotypy and pelt biting, can all be affected by stress and have been found to be important welfare indicators in many studies. 3. Past experience and genotype interact to affect these responses. Factors unrelated to welfare can also confound them. Thus all welfare measures must be interpreted carefully in the light of factors which may affect them. 4. Potential welfare indicators which have not proved very useful for mink include litter size, kit growth rates, body weight, pelt condition, and heterophil: leucocyte ratios. 5. All these measures, and also mortality and morbidity (including bite wounds), vary between mink farms, sometimes because of known differences in husbandry, but sometimes for reasons which are unclear. 7KH ZHOIDUH RI IDUPHG PLQN The welfare of farmed mink has been reviewed before, for example by Nimon and Broom (1999), who considered all welfare indicators but emphasised issues of behavioural deprivation, and by the Utrecht Animal Welfare Centre (AWC 1999), who compared mink farming to other intensive farming systems. *HVWDWLRQ DQG SUHQDWDO VWUHVV Some potential pre-natal stressors do exist, including acute events such as overhead planes, transportation, and the chronic proximity of neighbouring animals. The effects of transporting pregnant females on their foetuses’ HPA function have not been investigated; however, one study has looked at its effects on males’ later reproductive performance. In this study it was found that males born from transported pregnant females showed reduced testicular development and sperm production, and often failed to mate. Such effects were not seen in males that had been born from transported pregnant females two years previously, or in the sons of these animals, showing that they were not due to genotype differences between imported and control animals, and also that they could be reversed with time. The
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