This story first appeared in the Feb. 12 issue of The Hollywood Reporter magazine. To receive the magazine, click here to subscribe.

She has only six minutes of screen time, but the now-infamous mama grizzly that mauls frontiersman Hugh Glass, played by Leonardo DiCaprio, in The Revenant has emerged as one of the year's most talked-about — and elusive — stars.

Director Alejandro G. Inarritu has declined to discuss exactly how he shot the bear attack, preferring to keep it a mystery — as he did last year when he chose not to describe how Birdman had been made to look as if shot in a single take. (Only after the movie won four Oscars did its VFX team admit how much CG work was involved in stitching separate shots together.) But this year, with Revenant — which had grossed $235.3 million worldwide as of Jan. 28 — nominated for a visual effects Oscar, the Inarritu-imposed code of silence hasn't been as absolute. Says the film's VFX supervisor, Rich McBride of lead effects house Industrial Light & Magic, "It was very much a VFX movie that we don't want peo­ple to think of as a VFX movie."

The bear, a CG creation, was inspired by Coola and Grinder, resident grizzlies at Vancouver's Grouse Mountain wildlife sanctuary, whom McBride photographed. After the bear was created in the computer, she was hand-animated. ILM software was used to achieve "the motion itself, as well as the nuance of the movement of the fur, flesh, muscle and for getting everything integrated into the plate with natural lighting," says McBride.

The live action was filmed during a three- to four-day period in a rainforest near the Squamish River in British Columbia. DiCaprio performed nearly the entire sequence himself, with only a couple of moments, like a tumble down a hill, when a stunt performer stood in for him. McBride declined to elaborate further, but Glenn Ennis, listed as a stuntman in Revenant's credits, has stepped forward in the media to claim that he, outfitted in a blue suit, played the bear in the bear-on-man portions of the sequence.

As in Birdman, McBride says "very long takes" were used, with editing and CG making the scene appear as one continuous shot. To mate the CG bear with live action, the VFX team added elements like CG moss to "connect the bear to the ground by creating the contact point where she's stepping, brushing up against something. Sometimes you could sell a movement with the smallest bit of foliage interacting with her."

During the 14th annual Visual Effects Society Awards, which were held at the Beverly Hilton hotel in Los Angeles on Feb. 2, the bear got its awards show moment: The Revenant won three trophies, including for best animated performance for the bear and best compositing for the bear attack. read more