Status van de Nederlandse otterpopulatie : Genetische variatie, mortaliteit en infrastructurele knelpunten in 2020

Summary

The Dutch otter population is surveyed each year for the Ministry of Agriculture, Nature and Food Quality to monitor its genetic status. Particular attention is given to roadkill mortality and a possible reduction in genetic variation as a result of inbreeding. The aim of the annual survey is therefore twofold: a) to closely monitor the genetic variation within the population, and b) to identify and localise roadkill hotspots. The total number of verified dead otters found in 2020 was 166, again a slight increase, but a significantly lower increase than in previous years. The most likely explanation for this is a reduction in traffic intensity as a result of the Covid-19 measures. The main roadkill hotspots where many otters are still killed were identified for each province. The possibility that relatively more otters were killed on roads due to barrier effects of pumping stations, weirs and sluices located in the vicinity (within a 250 m radius) was also investigated. From DNA profiles obtained from roadkills it can be concluded that the total genetic variation within the Dutch otter population is reasonably stable. The high number of roadkills forms a statistically reliable sample as they represent about 25% of the total number of animals in the population.