Canadian wildlife management policies encourage hunters to pursue male bears, conserving females while maximizing the number of bears harvested, the Edmonton university said in a news release. But harvesting based on sex selection has reduced the number of males compared to females in polar bear populations across the Canadian Arctic, said the study's lead author, Peter Molnar, a Ph.D. candidate in the university's biological sciences department.

The mathematical model developed by Molnar, under the supervision of polar bear expert and faculty member Andrew Derocher, has given the researchers the ability to predict how many male bears are needed in an area compared to the number of female bears to maintain successful mating.

The team determined if the male-to-female ratio drops below a critical threshold, the model predicts a sudden collapse in fertilization rates. The threshold depends on whether the area has a high- or low-density polar bear population.

The findings were published in the online edition of the Proceedings of the Royal Society, an academic journal based in Britain.