This article, the first of the group I posted above, indicates that it can take as little as two months for a body to become unrecognizable in that environment:
"The remains were found more than two weeks ago on a riverbank, and had likely been exposed to the elements and wild animals for at least two months, police said.
The body weighs 75 pounds -- which is low due to decomposition -- and is five foot three to five foot four, with wavy grey medium-length hair.
Because of the state of the remains, the womans skin colour and age are not known. There are no identifying marks on the body."