Because of the dominance of older and stronger boars, sexually mature young males often do mat mate.
Courtship begins soon after bears leave their winter dens.
Mating can be noisy to the point of boisterous. Competition among boars ranges from brief displays of dominance to protracted fights resulting in serious injury. In the case of the Kodiak brown bear, implantation generally does not occur until the female is ready to den for the winter. In this manner, sows have a chance to achieve optimum physical condition during the fall feeding season before beginning their gestation period. Sows that fail to achieve adequate physical condition may abort and re-absorb the fertilized ovum.