Deer-vehicle collisions in Denmark

Vehicles collide with hundreds of thousands of deer on European roads each
year. This leads to animal deaths and suffering, economic damage and risks
for human safety, making the reduction of road mortality a major field in
conservation biology. In order to successfully reduce roadkill, we need
improved knowledge regarding spatio-temporal patterns of deer-vehicle
collisions (DVCs) on a landscape scale. Here, we analyzed >85,000
DVCs collected over 17 years in Denmark to investigate changes in the
number of DVCs over time and to find spatio-temporal patterns of DVC
occurrence. We used a use-availability design – originally developed for
habitat selection analyses – to compare DVCs involving roe deer (Capreolus
capreolus), red deer (Cervus elaphus) and fallow deer (Dama dama) with
random road locations on a landscape scale. This approach enabled us to
combine temporal (seasonal and diel variation), spatial (land cover, road
density and type) and other relevant variables (deer population density,
traffic, and deer activity) within the same analysis. We found that
factors related to infrastructure and land cover were most important in
explaining patterns of DVCs, but seasonal and diel changes, deer activity,
and population density were also important in predicting the occurrence of
DVCs. Importantly, patterns of DVCs were largely similar between the three
deer species, with more DVCs occurring at intermediate traffic density,
increasing forest cover, during dusk and dawn, and with increasing deer
activity and population density. The strong and consistent patterns found
here will allow the development of flexible mitigation measures. We
propose that our findings could be used to develop a spatio-temporally
flexible warning system for smartphones and navigation systems that is
based on existing map providers, making it a widely available and cheap
mitigation measure.