Territorial dynamics of female wolverines

University essay from SLU/Dept. of Ecology

Abstract: Spatial and social systems form the organisation of animals in space and time and areimportant aspects of animal ecology due to their effect on population dynamics andstructure. In this study I investigate territorial dynamics of female wolverines, withparticular focus on interannual territorial fidelity and reoccupation of territories vacated dueto death of territorial females. To do this, I used location data and den site locations of adultfemale 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. Residentfemales (n = 34) were monitored for a total of 145.9 wolverine years, and only twelvefemales moved from their territories one or more times during the study, resulting in a totalof 14 vacated territories. Hence, 9.6% of resident females moved from their territoriesannually. Fifty-eight percent of the females (n = 7/12) that abandoned their territoriesestablished new territories, with a mean distance of 11.7 km between dens in their old andnew territories.Sixteen (70%) of territories vacated due to death of a resident female (n = 23) werereoccupied by a replacing female. The mean territory overlap between the deceased femaleand her replacer was 75% (range 57-87). Sixty-nine percent of replacers (n = 16) occupiedvacated territories within a year. There was a new reproduction the first year after theterritory was vacated in 30% of all the vacated territories (n = 23). The time fromreoccupation to first reproduction in the territory was significantly longer for juvenile andsubadult replacers than for adult replacers. I found that 54% of the marked replacers weredaughters and 15% were granddaughters of the deceased female. Every time a daughterwas still present in the territory when her mother died, the daughter occupied the vacatedterritory.My results suggest that the spatial organization of female wolverine territories inScandinavia is characterized by long-term stability, as vacated territories are generallyoccupied by new individuals rather than absorbed by neighbours. Furthermore, in apopulation that is saturated with territories, deceased females are generally replaced byfemales from the local population, and primarily daughters if they are still present in theterritory when their mother dies. Hence, local density of territorial females is resumedwhile emigration is decreased, which can have implications for adjacent populations. I alsoshowed that the time from reoccupation to first reproduction for the replacing femalesvaried considerably. This is important from a Swedish management perspective, as thelocal density, and possibly predation pressure, might recover quickly after removal ofterritorial females, while the amount of economical compensation, based on number ofwolverine reproductions, to reindeer herding districts for predation losses is reduced untilnext reproduction in the territory. My study shows that the reoccupation process and timeto next reproduction, effects on local density and emigration are important factors toconsider when using removal of individuals to decrease predation pressureThe demographic importance of female survival for population growth is furtheremphasized by my results, which shows the strong influence of adult female survival onterritorial dynamics and dispersal, and hence its effect on a larger scale.

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