Detection of denning polar bears with forward-looking infrared (FLIR) imagery. Polar bears construct maternal dens of ice and snow throughout their circumpolar range. In the Beaufort Sea region of northern Alaska, most dens have been found on the flat coastal plain. Hydrocarbon extraction is now occurring or planned along 100 miles of the Beaufort Sea coastline. If development pushes, as expected, into the National Petroleum Reserve, the scope of development could include up to 2/3 of the northern coastal region of Alaska. Human activities are a potential threat to denning polar bears, and resource extraction has generated significant concern for the welfare of denning polar bears and their habitats. While numbers of humans and their activities have increased in northern Alaska, numbers of denning females present along the coast also have increased. Therefore, the probability of disruption of maternal denning could increase in the future. Although the distribution of sites used by polar bears for denning in the past has been described, probabilistic prediction of future denning locations have not been possible. In this study, we will test whether forward looking infrared (FLIR) scanners can consistently detect polar bears occupying dens under the snow of Alaska's northern coast. Pregnant polar bears will be captured fitted with satellite radiocollars and released during the autumn of 1997. Satellite transmitters (PTTs) will transmit daily through the predenning and denning period. Transmissions will convey location, temperature and activity level of the bear, allowing us to ascertain the timing and location of den entry. The effectiveness of FLIR to detect denned bears will be tested in December-February by which time dens will be well established and covered by a thick snow layer. A series of overflights will be recorded on videotape for each den located. Overflights will differ in altitude, speed, view angle, and ambient conditions. A panel of observers, then, will test visibility of bears in dens, and we will record whether they successfully see the dens. After den abandonment in spring, we will return to each den to record habitat features that could influence detectability of the den by FLIR.