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Measuring fecal glucocorticoid metabolites (fGCMs) is a widely used, non-invasive method for studies of stress in vertebrates. To study physiological responses in wild Arctic foxes (Vulpes lagopus) to perceived stressors such as fluctuating food availability, occurrence of competitors and predators and disturbance from human activities, a species-specific physiological validation of a method to evaluate adrenocortical activity is needed. Here we used 15 captive Arctic foxes (both males and females and juveniles and adults) to investigate fGCM concentrations following ACTH injection (physiological validation), or handling alone and compared them with their respective baseline concentrations prior to the treatments. A 5α-pregnane-3ß,11ß,21-triol-20-one enzyme immunoassay measured significant fGCM increases following both treatments. The time lags to reach peak fGCM values were 9.3 ± 1.3 h and 12.8 ± 1.7 h for ACTH and handling treatment, respectively. Concentrations of fGCMs varied a lot between individuals, but not attributed to sex nor age of the foxes. However, we found a negative relationship between boldness and fGCM concentrations. Faecal glucocorticoid metabolites concentrations did not change significantly over a period of 48 h in samples kept at temperatures reflecting winter and summer means. This would allow the collection of samples up to two days old in the wild regardless of the season. We conclude that our successfully validated method for measuring fGCMs can be used as a non-invasive tool for studies exploring various stressors both in wild and captive Arctic foxes.

Providing captive foxes with relevant enrichment objects may support their ability to cope with barren housing systems and thus have positive welfare effects. The relevance of enrichment objects is, among others, related to animals’ preference that should be examined prior to supplementing their housing environment. In this study, we assessed 30 juvenile, singly housed silver foxes’ short-term preference for five different oral enrichment objects based on their immediate use of the objects when they were given simultaneous access after one week of deprivation. Also, wear and tear after one week of continuous access was assessed as a measure of use and to estimate the robustness and durability of various objects. A cattle femur bone was clearly the first ranked object (P ≤ 0.05), followed by a rawhide bone, a mutual pulling device mounted between neighbouring cages, and straw and a plastic cube as the least used objects. All of the objects were, to a various degree, gnawed by the foxes. After one week of use, about 30% of the cattle bone mass was consumed, compared to about 88% of the rawhide bone mass. Although the plastic cubes were almost indestructible and therefore durable objects their low ranking do not necessarily make them good enrichment objects for foxes. Offering meat bones to captive foxes provide the animals with biologically relevant stimuli that elicit oral manipulation and play, behaviours with potential rewarding effects to the animals.

Measuring glucocorticoid metabolites in faeces has proven a useful, non-invasive method to monitor adrenocortical activity in several farm and wild species. Unlike plasma cortisol, whose sampling requires restraint and blood draws, faecal cortisol metabolites (FCM) may be particularly suitable for farmed silver foxes as these animals are sensitive to handling by humans. Prior to using FCM as a potential indicator of stress in silver foxes, however, a proper physiological and/or biological validation is required. Here, we determined FCM concentrations in 30 silver foxes (10 adult vixens, 10 juvenile females and 10 juvenile males) every alternate hour for 24 h after 1) an increase in cortisol induced by injection with synthetic ACTH (hereafter ACTH), and 2) a 2 min period of handling and restraint. Baseline FCM values, recorded every fourth hour for 24 h before the ACTH and handling treatments, served as controls. FCM values increased significantly following ACTH injection (P = 0.0001) and handling (P