Leonardo DiCaprio is calling The Revenant shoot one of the most difficult in his life, and by difficult, he means sleep-inside-an-animal-carcass difficult.

In an interview with Yahoo! Movies, the Golden Globe winner detailed the treacherous circumstances he had to endure for the highly anticipated period drama.

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"I can name 30 or 40 sequences that were some of the most difficult things I've ever had to do," the 40-year-old actor said. "Whether it's going in and out of frozen rivers, or sleeping in animal carcasses, or what I ate on set."

Directed by Oscar-winning Birdman filmmaker Alejandro González Iñárritu, The Revenant follows 1820s frontiersman Hugh Glass (DiCaprio) as he sets out on a path of vengeance against those who left him for dead after a bear mauling.

Part of the film was shot in the Canadian wilderness, where the cast was forced to battle the elements.

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"[I was] enduring freezing cold and possible hypothermia constantly," DiCaprio recalled. "I certainly don't eat raw bison liver on a regular basis. When you see the movie, you'll see my reaction to it, because Alejandro kept it in. It says it all. It was an instinctive reaction."

In one of the trailers for the film, viewers are given a glimpse at the bear attack that looks real enough to prompt the question: How did they do it? While DiCaprio didn't give away any secrets, he did disclose that the stunt involved cables and "a tremendous amount of rehearsal."

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Check out the heart-pounding trailer below.

The Revenant, also starring Tom Hardy and Domhall Gleeson, opens in limited release on Christmas Day before expanding nationwide on Jan. 8.