As for the Elk, Wapitis and Red Deers are two different species, despite the fact that hybridizations are said to be possible. The Red Deer is smaller that the Wapiti or the Maral.

The differences in the size of the Moose are mainly due nowadays to the terrain and the food it offers. According to old reports there were also in Europe in the past very large Mooses near to those of BC/Canada for example.

The same applies to the Wisent as well as the Bear, all a question of the terrain that is still available and the food that this terrain offers.