One of the highlights of Churchill’s polar bear season are the raucous playfights of the large male bears. As the season progresses and the temperatures drop, the resident bears become more active and begin to playfight. Some spar and break off, others partner up, playing and resting together for a few days. Certain bears will spar with a wide variety of bears over the season or even throughout the day!
Fights usually start when one bear ambles over and signals his intent, with a lowered head or even a nudge or bite. The two bears then ‘mouth’. Face to face, they open their jaws wide, moving and seemingly sizing each other up. Soon, the intensity builds. They wrestle, trying to wrap a massive paw around the other’s neck.
Inevitably, one, often both, will rise on his back haunches and lunge forward to shove or tackle his opponent.
There seems to be a fair amount of strategy. Each bear, especially the smaller one, waiting for the moment when his opponent is maybe a little off balance. In many of the playfights, one bear will be generally dominant, however, this hardly means that the fights are one-sided. The stronger bear often ‘lets’ the smaller bear compete, seemingly enjoying the thrill of the fight more than the victory. Fights are rarely serious with blood drawn only occasionally, usually when two bears are a little too evenly matched.
Playfighting is also common with cubs. Young bears will frolic and fight for hours on end, with the larger, usually male, cub dominating. Adult females with a single cub will also ‘spar’ with their offspring.
Subadult bears, three or four years old, may team up, likely to compete with larger bears for food and dominance. These partners may also be seen playfighting, albeit in slightly less dramatic bouts than the largest males. It is thought that some of these teams are siblings, recently separated from their mother. They may stay together to increase their chances of survival during the first full season on their own.
The Competition for Mates
With mating season half a year away, the playfighting in October and November seems to be just some good ol’ rough and tumble fun. This fun, however, may also allow the bears to size up potential competition for mates.
During this playfighting, the polar bear’s testosterone is amongst its lowest annual levels. This is not the case in spring. Male polar bears’ testes begin to drop in mid-winter and they are ready to mate as early as March. Peak mating season occurs in late April through May and the competition is fierce. Driven by the scent produced during the female’s estrous, males have been recorded tracking potential mates for over 100 kilometres (60 miles). Of course, other bears usually have the same idea…
The mating continues over several days, the duration of which the male must fend off spirited competitors. Vicious battles between large male bears often result in scars, wounds, and broken bones.
An injured jaw or shoulder can mean the end for an otherwise healthy bear. Unable to hunt effectively or defend their food, it is a slow decline; making for a frustrated and dangerous bear.
Injured bears are not the only frustrated ones. Though sexually mature by three to five years of age, most male polar bears do not breed until close to ten years old. Most are unable to compete with the larger males and must simply bide their time.
This competition and ultimate dominance of the largest bears results in significant ‘sexual dimorphism’ (the size differences between males and females) among polar bears. Only the largest males are consistently successful in securing mates while most females reproduce regularly. This has created a genetic makeup where male polar bears are usually one and a half times larger than females. Voila, sexual dimorphism!