Genetische monitoring van de Nederlandse otterpopulatie : Ontwikkeling van populatieomvang en genetische status 2018/2019

The Dutch otter population is surveyed each year for the Ministry of Agriculture, Nature and Food Quality to monitor its size, distribution and genetic status. DNA is isolated from spraints and tissue from dead individuals, and data is obtained on the demographic processes of reproduction, mortality, immigration and emigration. The resulting information is also used to detect changes in the spatial distribution and size of the population. Based on the DNA profiles identified during the monitoring in 2018/2019, the population is now estimated to consist of approx. 360 individuals. The population has therefore grown steadily. The number of traffic victims increased strongly in 2018 and was proportionately larger than the increase in population size. The list of roadkill hotspots has been updated. The total amount of genetic variation at the population level seems to be stabilising, as does the average genetic variation within individuals. This underlines the importance of immigration of otters from German populations near the Dutch-German border. Although incidental, this was more frequent than in the previous year. A particularly hopeful sign is that there appear to be three different immigration routes, through the provinces of Groningen, Overijssel and Gelderland.