In the debate over the possibility of oil drilling in the Arctic National Wildlife Refuge in Alaska, polar bears play an important, if silent, role.

At issue is whether oil development, especially seismic testing to find oil reserves that would be conducted long before any drilling occurred, can be undertaken without harming the animals, which have been hit hard by climate change.

A new study casts doubt on the effectiveness of what is considered a state-of-the-art tool to help industry avoid injuring or disturbing polar bears by detecting their dens in the snow. Over more than a decade on the North Slope of Alaska, the study found, oil companies located fewer than half of the known dens of maternal bears and their infant cubs using airborne instruments called forward-looking infrared, or FLIR, cameras.

“We wanted to make sure that we throw up a cautionary flag,” said Tom Smith, a wildlife ecologist at Brigham Young University and the lead author of the study, which was published Thursday in the journal PLOS ONE. The oil industry “needs to acknowledge that even with the best conditions, you’re going to miss bears,” added Dr. Smith, who is also a scientific adviser to Polar Bears International, a conservation group that provided some of the funding for the study.