Werner Herzog's stark new documentary

Speculation continues to simmer over which major films will be nominated for which Oscar on 31 January. However, there's one safe bet: March of the Penguins, that cute little movie about an Emperor-penguin colony, will almost certainly be nominated for best feature-length documentary, and will probably win the prize. Meanwhile, the director Werner Herzog's Grizzly Man, a much tougher-minded documentary set in the other frozen side of the globe, which offers a more brutal portrait of nature, both human and animal, has not even made the Academy's long list of films eligible for the best-documentary award.

I tell Herzog that I'm surprised that Grizzly Man, his most financially successful movie ever, isn't up for nomination. "Your surprise honours me," he says, chuckling, but it's no shock to him. He knows that it's not the kind of uplifting/Holocaust-themed/comfortingly liberal story that Academy voters usually honour. Instead, Grizzly Man is a formally complex film, combining footage shot by Herzog and his crew with that made by the decidedly problematic Timothy Treadwell, a self-invented eco-warrior who spent 13 summers camping among the grizzly bears of Alaska's Katmai National Park. "What makes the film rather unique is that I'm having an ongoing argument with the leading figure throughout," Herzog says. "Not a nasty argument - it's like the way I argue with my own brother, whom I love."

A reformed addict who, despite his eventual marginal celebrity, had problems fitting into society, Treadwell saw the bears as his salvation and his surrogate family, giving them fanciful names such as Mr Chocolate, Downey, Sgt Brown. He filmed the bears, some scene-stealing foxes, and himself incessantly, capturing some extraordinary moments of bear behaviour, as well as many narcissistic hours of himself talking to camera as though he were the star of his own nature documentary, sharing his loneliness, rhapsodising about the bears in his twee high voice, and ranting against his supposed enemies in the park service. Although he often had people staying with him, on camera he presented himself as a "lone warrior," single-handedly defending the bears against poachers, even though there is little risk of that in Katmai. So accustomed were Treadwell and his girlfriend, Amie Huguenard, to reaching for the camera when a bear came near, one of them had turned it on, but not removed the lens cap, when a bear attacked, killed and ate them in October 2003.

Viewers are informed at the start of the film how Treadwell perished, which endows the footage of him declaiming that he "would die for these bears" with a tragic irony. The drama lies in watching him unravel, while interviewees explain to Herzog the sequence of events and mistakes (such as getting too physically close to the bears in the first place) that lead to his and Huguenard's deaths, reaching back to his seemingly average childhood when he showed a passion for animals.

Throughout, as the footage that Treadwell shot unfolds, Herzog's voiceover interjects the director's comments, underscoring his and Treadwell's very different attitudes towards nature. "What haunts me is that, in all the faces of the bears Treadwell filmed, I discover no kinship, no understanding, no mercy," Herzog says at one point, as the image freeze-frames on the face of a bear, perhaps the one who would kill Treadwell. "I see only the overwhelming indifference of nature. To me, there is no such thing as a secret world of the bears. This blank stare speaks only of a half-bored interest in food."

Fans of Herzog's films, which include such classics as Aguirre: The Wrath of God (1972), Nosferatu (1979) and Fitzcarraldo (1982), might be reminded at this point of the opening of The Enigma of Kaspar Hauser (1974): beautiful images of a river, a boat, a field, and Pachelbel's Canon on the soundtrack. "Can't you hear the screaming?" a subtitle asks, subverting the romanticism. Herzog's stance towards nature is in direct opposition to the cuddly anthropomorphism of March of the Penguins. In a now famous line in Grizzly Man, he says: "I believe that the common denominator of the universe is chaos, hostility and murder."

Thankfully, Herzog is more playful in conversation. I put it to him that the film chimed with many of his other films in its opposition to the"tree-hugging" view of nature. "Yes, tree-huggers, they're the enemy. Please write that in capitals: THE ENEMY," he says, laughing. But wasn't Treadwell a bit of a tree-hugger? "Not completely, no," he says. "There's a New Ageism to him that I loathe, but it's OK. I always said that it wouldn't be a wildlife film, but a film about human nature. It's a very human story, with all the defeats mixed with the victories and the mistakes. And the tragedy, too."

Indeed, one of the most powerful moments in Grizzly Man is when Herzog listens through headphones to a recording of Treadwell's death and Huguenard's screams, watched by Jewel Palovak, Treadwell's friend and heir. Instead of playing it for the audience, as apparently some of the producers urged him to, Herzog tells Palovak that she should destroy the tape. "It was so terrifying that it was instantly clear that, number one, we were not doing a snuff movie, and number two, there is such a thing as the dignity and privacy of your own death, and you just don't touch it," he tells me. "It was instantly clear that it would not be in my film. Period."

'Grizzly Man' opens on 3 February