The expression occurs twice in the D.V., but much oftener in the A.V., and R. V., where it is in several places a substitute for the awkward “beast of the field”, the Hebrew name of wild animals at large. The first time we read of “wild beasts” in the D.V., it fairly stands for the Hebrew word zîz [Ps. lxxix (Hebr., lxxx), 14], albeit the “singular wild beast” is a clumsy translation. The same Hebrew word in Ps. 49:11, at least for consistency’s sake, should have been rendered in the same manner; “the beauty of the field” must consequently be corrected into “wild beast”. In Is., 13:21, “wild beasts” is an equivalent for the Hebr. Ciyyîm, i. e. denizens of the desert. This word in different places has been translated in divers manners: demons (Isaiah 34:14), dragons (Psalm 73:14; Jeremiah 1:39); it possibly refers to the hyena.

Source: [http://en.wikipedia.org/wiki/List_of_the_animals_in_the_Bible]