A Boy and His Dog (1975)

Vic (Don Johnson) is a libidinous 18-year-old traversing the post-apocalyptic desert of 2024, in the company of his telepathic dog, Blood. When the pair encounter an underground community, the leader's daughter, Quilla Holmes (Susanne Benton), seduces Vic into their fold, separating him from Blood, who's left to survive on his own.