Scenes originally from the movies Mundo Canibal (1972) (crocodile being killed with a small knife, and a woman being killed and eaten by cannibals), O Último Mundo dos Canibais (1977) (Me Me Lay's death sequence), and Busca sem Fim (1978) (castration scene, footage of a snake eating a monkey, and a man being pulled into the water by a crocodile), were edited into this movie.
The antagonist character of Jonas, and his commune and of the climatic mass suicide, was inspired by the Jim Jones People's Temple cult in Guyana who committed mass suicide in November 1978 resulting in the deaths of over 900 people. Given its proximity to the real events, "Eaten Alive!" is one of the earliest fiction films to depict the Jonestown Massacre.
Years after the filming, Umberto Lenzi said that if he had know that Robert Kerman was a porn actor, he wouldn't have hired him (neither in this nor in Holocausto Canibal (1980))(EDIT: Lenzi did not direct Cannibal Holocaust). Coincidentally, Jake Teague (Logan) was also a porn actor, and as Kerman, also appears in both movies.
With the exception of the snake killed by Ivan Rassimov, all the real animal deaths were archive footage from Mundo Canibal (1972), O Último Mundo dos Canibais (1977) and Busca sem Fim (1978).