Forests are not usually teeming with water bodies. In other words, there are only a handful of lakes, ponds, or other small bodies of water that quench the thirst of a lot of animals that live in nearby wildlife areas. As animals repeatedly drink water from the same source or drink water with bacterial profiles that are not drastically different from each other, their bodies tend to develop a sort of resistance to such ‘bad’ water. Their immune system recognizes certain bacteria through repeated encounters with them and becomes more effective in dealing with them.
Moreover, most mammals have a finely developed sense of smell, which helps them determine to a certain extent whether a water body is bacteriologically active. When they encounter such a body, they often simply pass on the idea of drinking from it.
