In the description of the Sleep spell (PHB p276):
This spell sends creatures into a magical slumber. Roll 5d8; the total is how many hit points of creatures this spell can affect. Creatures within 20 feet of a point you choose within range are affected in ascending order of their current hit points
Is there any reason not to allow a wizard to find food by launching this spell in a rather luxuriant environment with supposedly a lot of game (i.e. jungle), or on a river?