No abstract

Genetic rescue can facilitate the recovery of small and isolated populations suffering from inbreeding depression. Long-term effects are however complex and examples spanning over multiple generations under natural conditions are scarce. The aim of this study was to test for long-term effects of natural genetic rescue in a small population of Scandinavian Arctic foxes (Vulpes lagopus). By combining a genetically verified pedigree covering almost 20 years with a long-term dataset on individual fitness (n=837 individuals), we found no evidence for elevated fitness in immigrant F2 and F3 compared to native inbred foxes. Population inbreeding levels showed a fluctuating increasing trend and emergence of inbreeding within immigrant lineages shortly after immigration. Between 0-5 and 6-9 years post immigration, the average population size decreased by almost 22 % and the average proportion of immigrant ancestry rose from 14 % to 27 %. Y chromosome analysis revealed that two out of three native male lineages were lost from the gene pool, but all founders represented at the time of immigration were still contributing to the population at the end of the study period through female descendants. The results highlight the complexity of genetic rescue and suggest that beneficial effects can be brief. Continuous gene flow may be needed for small and threatened populations to recover and persist in a longer time perspective.

Nature‐based recreational and tourism activities can exert significant direct and indirect impacts on wildlife, through behavioral, physiological and distributional changes. Despite many studies demonstrating such changes, few attempts have been made to quantify the fitness consequences and evaluate their biological significance. Helagsfjällen in Sweden is a core area of the endangered Fennoscandian arctic fox Vulpes lagopus, and a popular area for recreational tourism. Some dens in the area experience daily disturbance from tourism during the summer season, while others are virtually undisturbed. We used a long‐term dataset (2008–2017) of 553 juveniles in 74 litters to investigate summer juvenile survival, which is an important fitness component for the arctic fox. We found that the mean juvenile survival rate increased from 0.56 at undisturbed dens to 0.83 at disturbed den during years of decreasing small‐rodent abundance, where predation on the arctic fox is presumed to be highest. We suggest that the increased survival could be mediated by a human activity‐induced predator refuge for the arctic foxes in close proximity of trails and mountain huts. Our study demonstrates a possible positive indirect effect of nature‐based tourism on wildlife and is one of a few studies attempting to quantify this impact. It highlights the importance of context for how animals are affected by disturbance. We also demonstrate that studying how the effects of tourism activity vary depending on the context could provide opportunities for identifying the mechanisms behind these effects, which can be an important link between scientific research and the management of wildlife and tourism activities.

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.