It's actually part of a famous, much longer recording of similar grunts, howls and fairly bloodcurdling screams, made in the 1970s and purported to be a group of 'sasquatch'.
Needless to say, the cryptological claims for the origin of these sounds are cobblers, but the recording is quite noteworthy for the brilliantly wide range of sounds the fellow could produce by skilful vocalisation.
I think I might get the CD of the full recording, load it up on a music player and take some speakers out with me the next time I'm remote wild-camping, and give some unsuspecting campers a fright.
Anyway, the controversy continues over whether the recording is real or a hoax, but the fact remains it sounds pretty good, making it a damned fine hoax indeed.