The ice on Hudson Bay usually lasts well into summer but, by the end of July, the bears are back on shore. As wind and ocean currents push the dwindling ice floes down the coast, the polar bears begin to swim ashore. This begins a three to four month ‘fast’ where the bears will not have access to their main food source.
Pregnant females and mothers with cubs come ashore first. They generally leave the ice as it passes Wapusk National Park and the maternity denning area. This can be up to two weeks prior to the final breakup, occurring near Kaskatamagan and the Manitoba/Ontario border.
They do this for several reasons. One, females are fairly site specific, many of them return to an area within forty kilometres (25 miles) of their birthing den. Also, it seems the extra seals are just not worth the extra distance. Prime seal hunting season is coming to an end and the energy acquired from another couple seals is just not worth the long walk back to the denning area.
It is the large males that ride the dwindling ice to the bitter end, coming ashore in the southwest corner of Hudson Bay. From here, some begin their plodding migration back to the beach ridges of Cape Churchill. However, an increasing number now simply stay put for the summer, staying away from the hub-bub of civilization.
The bears that do venture north gather along the spits and gravel ridges on the coast, basking in the winds from Hudson Bay. They may dig pits as deep as one or two metres, down to the cool permafrost, and simply sleep away the day.
While looks may be deceiving, the living is not easy in the summer time. These large males are merely seeking temporary relief from temperatures that can reach over 20C-30C (70-90F) and biting insects that can be found in unreasonable and unrelenting proportions.
Bears cool down in several ways. They shed their winter coat, moulting each spring. Their fat layer is thickest on their rump, up to 4” thick on the largest males, so they will sit recumbent in day-beds, releasing heat from their belly and armpits.
Polar Bears have a special adaptation to release heat from their shoulders blades. They have two ‘radiators’, thin layers of muscle atop the fat layer. When a bear overheats, it will push blood to these muscles, in turn, releasing heat through the skin.
Mostly they rest, the largest bears losing up to 20lbs per week on land. However, their diet may be supplemented grass and sedges, peat, berries, seaweed and even lemmings, snow geese and even caribou.
The largest males may gather in groups of up to fifteen but usually ranging from two to six bears, sharing the best real estate. How these groupings fit in to the complicated hierarchy of polar bears remains to be seen.