Examensarbete Institutionen för ekologi Territorial dynamics of female wolverines

Spatial and social systems form the organisation of animals in space and time and are important aspects of animal ecology due to their effect on population dynamics and structure. In this study I investigate territorial dynamics of female wolverines, with particular focus on interannual territorial fidelity and reoccupation of territories vacated due to death of territorial females. To do this, I used location data and den site locations of adult female wolverines (n = 58), collected from 1993-2008 in and around Sarek National Park, northern Sweden. I found that female wolverines exhibited high interannual fidelity to territory. Resident females (n = 34) were monitored for a total of 145.9 wolverine years, and only twelve females moved from their territories one or more times during the study, resulting in a total of 14 vacated territories. Hence, 9.6% of resident females moved from their territories annually. Fifty-eight percent of the females (n = 7/12) that abandoned their territories established new territories, with a mean distance of 11.7 km between dens in their old and new territories. Sixteen (70%) of territories vacated due to death of a resident female (n = 23) were reoccupied by a replacing female. The mean territory overlap between the deceased female and her replacer was 75% (range 57-87). Sixty-nine percent of replacers (n = 16) occupied vacated territories within a year. There was a new reproduction the first year after the territory was vacated in 30% of all the vacated territories (n = 23). The time from reoccupation to first reproduction in the territory was significantly longer for juvenile and subadult replacers than for adult replacers. I found that 54% of the marked replacers were daughters and 15% were granddaughters of the deceased female. Every time a daughter was still present in the territory when her mother died, the daughter occupied the vacated territory. My results suggest that the spatial organization of female wolverine territories in Scandinavia is characterized by long-term stability, as vacated territories are generally occupied by new individuals rather than absorbed by neighbours. Furthermore, in a population that is saturated with territories, deceased females are generally replaced by females from the local population, and primarily daughters if they are still present in the territory when their mother dies. Hence, local density of territorial females is resumed while emigration is decreased, which can have implications for adjacent populations. I also showed that the time from reoccupation to first reproduction for the replacing females varied considerably. This is important from a Swedish management perspective, as the local density, and possibly predation pressure, might recover quickly after removal of territorial females, while the amount of economical compensation, based on number of wolverine reproductions, to reindeer herding districts for predation losses is reduced until next reproduction in the territory. My study shows that the reoccupation process and time to next reproduction, effects on local density and emigration are important factors to consider when using removal of individuals to decrease predation pressure The demographic importance of female survival for population growth is further emphasized by my results, which shows the strong influence of adult female survival on territorial dynamics and dispersal, and hence its effect on a larger scale.