Ruggero Deodato has said in several occasions that real animal deaths sequences were archive footage added by the producer after the filming, during the editing process. This is not completely true. Some of them are actually archive footage, but other (like the crocodile killing) were filmed for the movie.
The film was originally conceived as a sequel of sorts to Umberto Lenzi's Sacrifice! (1972). Lenzi was originally attached to direct, but the project fell through when the producers refused Lenzi higher payment. Although the idea was eventually scrapped, the original "sequel" concept is still readily apparent, as Me Me Lai and Ivan Rassimov star in both films.
First part of Ruggero Deodato's "Cannibal Trilogy" also including Cannibal Holocaust (1980) and Cut and Run (1984).
The conception of the alternative title "Jungle Holocaust" was spurred by the popularity and notoriety of Ruggero Deodato's later film, Cannibal Holocaust (1980).