the cages are extremely small (15 cm W x 15 cm H x 45 cm L). It also has no effect on corticosteroid levels. Similarly, no differences in cortisol levels nor eosinophil levels were found between Pastel pairs experimentally housed in small (0.10 m2, standard (0.27 m2) or large (1.05 m2) cages. Similar small, standard and large cages in another study also caused no difference in growth, even though kits in small cages ate significantly less (Hansen et al. 1994). This result may be because stereotypy was, paradoxically, highest in the large cages. Perhaps relatedly, adrenal weights were found to be higher, and eosinophils lower, in large cages. However, the effect of cage size may well depend on what sizes are being compared, and whether the smaller options actually decrease activity. The following studies have investigated the resources available in young minks’ environments. Pairs of Pastel kits given nest-boxes (as is standard on farms), plus a raised shelf and/or wire cylinder, displayed less stereotypy than pairs of kits without these additions (Hansen et al. 1994). In the former group, the nest-box was used 61% of the time, the shelf was used for about 15% of active behaviour, and the shelf was used more than the cylinder. The lack of a nest box also increases kits’ plasma cortisol, increases HPA responsiveness to ACTH challenge, and decreases eosinophil number, and reduces pelt quality. Kits have been observed to play with straw, a possible enrichment provided in Scandinavia though not always in the Netherlands. Kits given a bath of water will perform ‘boisterous social play’ in it, and also retrieve objects from it without reinforcement. Kits given a tray of water also used it, and showed anticipatory increases in activity, like those seen before feeding, when the water was renewed; however, the resource had no effect on stereotypy or eosinophil levels, and indeed caused the kits to grow more slowly. Even a larger bath will not decrease stereotypy or tail-biting levels compared with control kits, although removing this resource after 6-7 months of age does has deleterious effects on these behaviours. Finally, Jeppesen and Falkenberg (1990a,b) experimentally studied the use of play-balls supplied at the age of 6 months. At this late stage, these objects had no overall effect on pelt-biting, cortisol levels, or eosinophil levels. They increased activity levels, and in females, also increased stereotypy. However, the kits interacted with these balls for the full four weeks of the study (though use did decline over the period), and the balls caused a decrease in time in the nest-box, and an increase in curiosity, manifest as looking at human observers. Thus enrichments and toys seem to have potential to improve the welfare of juveniles, obviously more so than minor cage size changes. However, it is clear that many potential enrichments (e.g. ones involving food or water; see e.g. AWC 1999, Mason et al. 2001) have not been tried, and that there is still a great need for preference studies and other investigations of the relative merits of different enrichments. Welfare of family-housed kits in modified cages An alternative housing system (the family system) involves leaving mink in complete family groups instead of weaning them into pairs, and housing them in several inter-connected cages so that their stocking density remains approximately the same as for pair-housed animals. This now occurs for some 20% of Dutch mink kits. The welfare pros and cons of this system are described below. The potential benefits of this system are numerous. This system does not involve weaning, and so removes weaning stress; the kits receive much social stimulation
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