Use of experimental bait sites by wolverines

This study investigates the visitation frequency and rate of wolverines (Gulo gulo) at experimental bait sites originally designed for brown bears (Ursus arctos) in Dalarna, Gävleborg, and Västerbotten counties, Sweden, 2008-2012. Bait sites were either permanent, i.e., fixed location that could not be changed throughout the study period, or temporary, i.e., location that could be changed between study years. Bait sites were restocked weekly with bait, i.e., meat (ungulates or fish) and vegetable materials (i.e., corn and beet root). Two remote cameras were installed at each bait site to capture images of visiting animals. The goal of this study was to evaluate the visitation frequency of wolverines at bait sites, their duration of time spent at bait sites, and the time interval between consecutive visits. Further, I also evaluated different behavioral pattern displayed by wolverines during their visits at the bait sites. Wolverines were the third most common mammal species observed at bait sites, and the second most common mammal observed at the bait sites when considering only the North study area (Västerbotten). Overall, wolverines carried out 74 visits during the study period, and significantly more (~93%) were observed in the North. The average visitation rate for the study period was 3.7 visits per week and did vary significantly between weeks. Visitation frequency did not differ between permanent and temporary bait sites or season (spring/summer and autumn). The highest visitation frequency was observed in 2010. Wolverines are considered a nocturnal species, and I observed significantly more visits during the night hours (68.9%) in comparison to day hours. After the initial establishment of a bait site, it took wolverines an average of 42 days to visit this bait site for the first time. In a Norwegian study, it took wolverines an average of 72 days until the first visit of bait sites at hunting hides. The average time wolverines spent at a bait site was 6.3 minutes, and the majority (77.1%) of visits lasted shorter than 10 minutes. The average time between two consecutive visits at a bait site was 79 hours (~ 3 days) in a given year. The wolverine is listed as vulnerable (VU) in the red list of endangered species in Sweden, and is protected by several national and international regulations and directives. To manage this elusive carnivore can be demanding, and implementing an adaptive management strategy requires good knowledge of its distribution and population size. The study design applied in this study, with some adaptations, could be useful for population monitoring purposes. The most important adaptation would have to be to restock bait sites also during the winter season. In the course of this study, bait sites were removed when bear denning started in autumn and reestablished in spring after the end of the bear denning period. Population monitoring of 2 wolverines based on bait sites could provide insight into demographic patterns, conspecific and intra-guild competition, dispersal patterns, and individual wolverines could potentially be identified based on fur coloration and markings.

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