Depends on the animals, I suppose. In my garden pond which is in the middle of an estate with no water inlet I;ve had frogs, newts and water snails as well as a huge assortment of insect life appear as if by magic. Apparently the spawn and seeds can travel on birds and animals which use the ponds for drinking etc or on plants bought in for the pond.Nature is a wonderful thing, if the enviroment is right it will find a way to use it
Kids ask all the time- how did the yabbies and fish get into the land locked dam that has no close river or other water flowing into it other than rain and run off.