人类动物 (1983)

Two men and one woman are the last people on Earth. They are reduced to savagery, mate with the woman, and they learn to survive on a deserted island. They discover a dog living on the island with them, and the woman takes the dog as a lover, too.
Shot on a shoestring with a cast of four--two men, a woman, and a canine--Eligio Herrero’s sci-fi fantasy Animales racionales (1983) is a scandalously ribald cult oddity. Existing in a dystopian future where nearly everyone on the planet has died, the film’s four survivors reduce themselves to primitive impulses in order to survive.
In a post-apocalyptic world, two men strive for the attention of the only remaining woman. The woman encourages the men to fight over her, rewarding the victor with sexual favors. When the men catch the woman sleeping with a German Shepherd, all hell breaks loose! There is no dialogue in the film, aside from grunts and groans.