Skar on Stockton Island

One of the greatest concentrations of black bears in North America is found on Stockton Island in the Apostle Islands National Lakeshore. Bears also regularly inhabit Sand and Oak islands, and, due to their mobility, may be found on just about any of the Apostle Islands.

About Bears...
Black bears (Ursus americanus) are the most numerous and widespread North American bear. Though the black color phase is most common, "black" bears can also be various shades of brown or even white. Adult males usually weigh from 250 to 400 pounds, while females range from 150 to 225 pounds. They are omnivorous and depend greatly on their sense of smell to locate food. Bears can run as fast as 30 miles per hour. Their curved claws enable them to climb trees. They are also powerful swimmers, enabling them to utilize habitat available on the islands.

Stockton Island's attractiveness to local bears seems to be a recent development. Occasional sightings were reported prior to 1984. In 1984 the University of Wisconsin at Stevens Point began an ongoing study of Stockton Island's black bears by capturing a 7- year-old female and a 6-year-old male (perhaps the only bears on the island) and fitting them with radio transmitting collars. From 1984 to 1994, 133 bears were captured and marked. These bears have been monitored over the years to determine their survival rate, productivity, movements and habitat use.

Cubs on Stockton Island

The Stockton Island bear population grew steadily, reaching a peak of about 35 by 1994. The population fell to about 25 bears in 1996. The density of 2.1 bears per square mile on Stockton (in 1994) was considerably higher than the average of 1.0 bear per square mile on the Wisconsin mainland.

As the density of bears on Stockton Island increased, several changes occurred in their life pattern. Home ranges became constricted showing considerable overlap with adjacent bears. Young females began breeding at a later age than their mainland counterparts. Numerous cases of cannibalism of yearling bears by adults were documented. The weights of cubs, yearlings and adult females became significantly lower than mainland bears.