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The Norwegian Environment Agency (Miljødirektoratet) and the Swedish Environmental Protection Agency (Naturvårdsverket) have co-developed standard methodology and guidelines for the monitoring of wolverines in Scandinavia, which have been implemented in both Norway and Sweden since 2014. To estimate size, and assessing trends, of the wolverine population in Scandinavia, wolverine reproductive areas (female territories) are annually surveyed during late
winter and spring to register whether reproductions have occurred. The population size is estimated based on the number of wolverine reproductions that fulfil the criteria for Documented or Considered as certain reproduction. The monitoring of wolverine reproductions, and registration of
data into the shared database Rovbase, is conducted by field staff from the County Administration Boards CAB (Länsstyrelserna) in Sweden and the Norwegian Nature Inspectorate (Statens Naturoppsyn) in Norway. In Sweden, the Sami villages (administrative units for reindeer herding)
aid the CABs by reporting suspected den sites, which can then be evaluated in the field by CAB field personnel.
During the 2017 census a total of 137 wolverine reproductions were registered in Scandinavia, a 27% increase compared to 2016. Of these, 97 reproductions were found in Sweden and 40 in Norway. This corresponds to a 67% increase in Sweden and a 20% decrease in Norway compared to 2016. Based on the number of wolverine reproductions during the last three years (2015–2017), the Scandinavian population size is estimated to 846 adult wolverines, defined as 1-year old or older (95% CI = 710–1067), which is similar to last year’s estimate for Scandinavia. Of the 846 wolverines, 324 wolverines (95% CI = 270–411) are estimated to be in Norway and 522 wolverines (95% CI = 409–696) in Sweden. The Norwegian part of the population has thus decreased with 7%
and the Swedish part of the population increased with 5% in comparison to the estimated population size in 2016. The model used to estimate population size, i.e. extrapolate number of reproductions to adult individuals in the population, accounts for annual variation in reproductive
success by using the average number of reproductions in the past three years.