Frogs spend part of their time on land, but they never venture far from water, for if they do not have a moist environment they will die. The reason is that the evaporation of the body fluids through the skin is so rapid that the frog must replace these fluids by periodically soaking itself in water.
I have seen a leopard frog, a species frequently used in biology classes, die within twelve hours because it was kept out of water. All amphibians lose a certain amount of water through the skin, but the rough-skinned toads lose it less quickly than the smooth-skinned frogs.
Consequently, toads, with their thicker skins, are often found some distance from water.