Several weeks ago, Alaska Public Media put out an article about how they have to map polar bear dens on Alaska's North Slope
Crew maps polar bear dens on Alaska's North Slope
It's interesting. I recommend the listen, so you can hear about the technology that they use to find these dens. It is incredibly impressive. By federal regulation no human activity can take place within one mile of the dens, so the oil companies hire these guys to fly around and mark dens so that they don't have to reroute their ice roads when they are looking for new wells to drill.