Light "attracts" animals. Meaning they will spawn in dark if there's some light and grass. So grow grass and light torches, fire, lava, or jack-o-lanterns so they will spawn.
Basicly any light source :biggrin.gif: In the middle of a forest surround your house in torchs and large amounts of wolves and such will wait outside Lol.
*QUESTION* what attracts animals?