It is possible that as they live far from the stream and water, they need to move for long distances when they need to reproduce or hibernate. As a result, the small size may be beneficial for moving for long distances. The migration results in the production of heat that can be rapidly lost by the small size species, whereas large species do not need to lose the overproduced heat. As a result, if the water-required species inhabits the region located far from stream water, the animals will have a smaller body size. To test the hypothesis, the habitat of the large and small salamander species could be changed.