Courtship begins soon after bears leave their winter dens.  Female estrus causes boars to become agitated, relentless, and even reckless.  "... He galloped after her, his hoarse panting plainly audible half a mile away.  ...The chase continued all day" (The Great Bear Almanac, Brown).  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.

Sows of all bear species, except the sun bear, exhibit an adaptation known as "delayed implantation".  The female's ovum (egg), fertilized at breeding, does not implanting the uterus until a more opportune time.  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.

One to three cubs (occasionally 4 or even 5) are born in the den in late January or early February.  With an initial body weight of under 1 pound, the cubs will occupy most of the sow's attention for the next 2-4 years (most sows drive their cubs off early in their third year).  Commonly, litters are separated by 3 or 4 years, but timing of litters (as well as size) depends upon age, health, food availability, human impacts, and the breeding activity of boars.

--information provided by the Kodiak National Wildlife Refuge