The month of May brings with it heavy rains, and these serve to water vast sedge flats. The tips of these grasses contain large amounts of protein, and bears flock to feed on them from May to July. But they have more than eating on their mind during that time frame.
May marks the beginning of the mating season for brown bears, while most black bears donâ€™t begin mating until June. Although the mating season extends for a handful of months, females are only able to become pregnant for about three weeks of that time period. Furthermore, they only consent to amorous activities during the first few days of the estrus cycle. For bears living fairly solitary lives, it can be tricky to find a mating partner at precisely the appropriate moment. Male grizzly bears have a home range of between 800 and 2,000 square miles, and sometimes they have to wander far across their home ranges to find a breeding partner. The same is sometimes true for female grizzlies, which have a home range of 300 to 550 square miles (black bears have a much smaller home range — up to 15 square miles for females and 40 for males).
In order to find their way to a female in estrus, males simply follow their noses. Bears have an acute sense of smell, equivalent to that of a dog. Males have been witnessed to walk 30 miles in a straight line, directly to a female in estrus, simply by following her scent.
Pronounced sexual dimorphism exists among bears, meaning that the males are much larger than the females. The largest bears have an advantage when it comes to mating because their size allows them to ward off competing males. However, it can also intimidate females and make them more difficult to woo. The act of courting an estrus female may take several days of simply shadowing her movements before she allows the male to come closer. Once they have established intimate behavior — grazing, playing and resting together — the female will permit her suitor to mount.
Competition among male suitors can become fierce, and it can result in serious injuries — lacerations, broken jaws and broken canine teeth, to name a few. But, although males sometimes fight viciously over females, this does not mean that females copulate with only one male during the mating season. On the contrary, each cub in a litter can potentially have a different father. Of course, the fathers' involvement lasts only as long as the courting process. Once the animals go their separate ways, male bears have played out the entirety of their role in their offspring's lives.