Overvåking av fjellrev i Sverige og Norge 2020

In 2016, the Norwegian Environment Agency (Miljødirektoratet) and the Swedish Environmental Protection Agency (Naturvårdsverket) developed a common methodology and standardized guidelines for the monitoring of arctic foxes in Scandinavia. The coordinated data collection and reporting was implemented in 2018, aiming to provide robust and unambiguous population estimates, as well as document the development in the Scandinavian arctic fox population over time. In 2020, the monitoring effort has been coordinated at all stages, from standardized data collection in the field, through quality assurance and reporting. This report presents the status for the various subpopulations (across national borders) and an overall population estimate for Scandinavia. In Norway, a monitoring program for arctic fox was established in its current form in 2003, in connection with the first arctic fox action plan. The monitoring in Norway is financed through yearly grants from the Norwegian Environment Agency. The Norwegian Institute for Nature Research (NINA) stands for expertise in prioritizing, overall national quality assurance and annual reporting, while the Norwegian Nature Inspectorate (SNO) coordinates the practical implementation of the work, divided into seven regions. In Sweden, a national monitoring program for arctic fox was established in 2018 and is coordinated by The Swedish Museum of Natural History (NRM). Since 2018, the overall national monitoring of arctic foxes in Sweden is funded by the Swedish Environmental Protection Agency and carried out by the county board (Länsstyrelsen), but a part of the field work is still financed from elsewhere and carried out by Stockholm University. According to the population model the arctic fox population in Norway and Sweden is estimated to 452 adult individuals (301-602, 95 % confidence interval) based on the last three-year period (2018-2020). The population model shows a steady growth in the population over the last 18 years. In 2020, 79 arctic fox litters were documented in Scandinavia, of which 43 in Norway and 36 in Sweden. The reproductions were spread over 16 subpopulations from Varanger (Finnmark), in the north, to Hardangervidda in the south. 51 of the litters were in cross-border areas, five were up north on the Varanger peninsula and the remaining 23 in the southern parts of Norway, of which 15 were in Finse/Hardangervidda. The number of litters and number of individuals detected from DNA (only in Norway), have previously been used as a foundation to present a yearly minimum estimate for the arctic fox population. This estimate has gone up and down depending on the abundance of rodents. The population model gives a more robust population estimate that also takes into consideration that not all individuals in a population is detected. In the arctic fox, number of litters and litter size follows the fluctuations in the rodent populations; with none, or few and small litters in bottom years, and many large litters in years with high abundance of rodents. This pattern was not so obvious this year, when large parts of the arctic fox distribution appears to have been in areas with few rodents. It’s somewhat surprising that we have so many litters in areas with few rodents. One explanation can be the intensive supplementary feeding that is carried out in several of these areas. A summary of previous years' monitoring results shows a significant growth of the arctic fox population in Scandinavia over the past 10-15 years. From 40–60 adult arctic foxes in early 2000 to about 450 today. Through management actions, we have succeeded in re-establishing subpopulations and reducing the distance between them. From Snøhetta in southern Norway, there is now a connection to the subpopulations in the east (Helags in Sweden) and in the north (Børgefjell/Borgafjäll) which continues further north to Junkeren – Vindelfjällen. The southernmost subpopulations in Norway also appear to be growing and re-establishments in intermediate mountain areas shorten the distance to other main populations such as Snøhetta – Sylan/Helags – Børgefjell/Borgafjäll. This positive trend is also confirmed by migration of arctic foxes between the subpopulations in Scandinavia. Increased migration has a self-reinforcing positive effect on the entire arctic fox population in Scandinavia, at the same time as the stability and viability of the population increases