Wikipedia wrote:The aurochs was far larger than most modern domestic cattle with a shoulder height of 2 metres (6.6 ft) and weighing 1,000 kilograms (2,200 lb).... It was regarded as a challenging quarry animal, contributing to its extinction.
Also according to Wikipedia, brown bears are no more than 680 kilograms. I assume the bears in game are brown bears, since there don't seem to be any others in the Scandinavian countries. Perhaps the challenge aurochs will offer would be equal to a bear? Could be scary considering they roam in herds...