Some of these pictures and descriptions may give away plot details that you might not want to know before watching the film.
This is an Action/Biography with a great cast based on the true story of the Granite Mountain Hotshots, a group of elite Arizona firefighters, spoiler alert, most of whom were killed in a firefighting disaster in 2013. That's not really a spoiler because it's why the movie was made and why we're watching it. The events and the characters are based on real people, but we know that means they made a lot of changes to fit it all in the limited length of a movie. One of those changes is a snakebite scene and plot thread that did not actually happen. Even though some of the people who were part of the story have complained about the movie's accuracy, after reading about the actual event, I think they stuck to the facts where it really matters. We see the strength and bravery needed to do the difficult and dangerous job of fighting fires and we get to know some of the firefighters and their families which makes us feel more connected to the tragedy.
The Snakebite
After his crew successfully defended a two-thousand-year-old juniper tree that is an icon of the community, we see one of the newest firefighters on the team, Brendan McDonough (Miles Teller) walking on a rocky Arizona hillside with another firefighter. McDonough steps next to a hidden rattlesnake and the snake strikes and bites him on the leg. His companion says "That's a rattlesnake".
Emergency Snakebite Treatment
We then see McDonough's bare leg with a bloody wound as he is wheeled on a hospital gurney. I'm already liking this a lot. They didn't try to cut and suck the venom or tie a tourniquet or anything, they just got him to the hospital as fast as possible. That's what you'd expect from a group of professional firefighters, but it's not what I expect from a fiction film, even if it's based on a real story.
The doctor asks McDonough to describe the pain, then they they put him in a hospital bed. His vitals look good and he's stable. His supervisor Eric Marsh (Josh Brolin) comes in and asks her if she is going to give him anti-venom but she tells them "No, and I'd rather not." When McDonough asks why she tells him she likes "...to save that bullet for when you really need it. Antibiotics and a morphine drip will do the trick." But he refuses any painkillers since he's a recovering drug addict.
The Severed Snake Tail Prank
Then see McDonough recovering in a hospital bed with fellow firefighter and friend Chris MacKenzie (Taylor Kitsch) snoring on a chair next to him. McDonough kicks him out for smelling bad and then MacKenzie pulls a severed rattlesnake tail out of a bag and throws it onto McDonough saying it's a little keepsake. We can hear the sound of the rattle. McDonough is startled and MacKenzie tells him they hunted for the snake for 45 minutes to bring him luck (from killing the snake.) McDonough holds the tail amused until a nurse comes in that MacKenzie becomes infatuated with.
Showing The Wound
The snakebite thread is not over yet. A day or more later, we're not told, we see the crew in a crowded saloon celebrating. Some of them demand to see McDonough's wound. When he protests, they pick him up and put him on the bar and rip off his bandage to expose the wound. It's done in good fun and left him no worse off.
Snakebite Recovery Saves McDonough
Finally, we learn that the snakebite is what saved McDonough's life by causing him to separate from the rest of the crew who perished in the fire. He is sent to climb a hill to be a lookout, observing the wind and weather and the state of the fire. When the winds changed and the fire exploded, he was evacuated by someone from another crew and never rejoined his own crew.
We see two at least two different live rattlesnakes in the movie. The first one appears to be a Western Diamond-backed Rattlesnake. We only see the tail of the second snake as it is crawling back into the rocks. It appears be a Red Diamond Rattlesnake. The severed rattlesnake tail looks the real tail of the second rattlesnake we see, but it could be a prop.
According to both the History vs. Hollywood website and the AZCentral website, the real life Brendan McDonough was not actually bitten by a rattlesnake. The reason he was put on the lookout duty that caused him to survive was because he was getting over the flu. So why did they insert a rattlesnake bite into the story that never really happened? Most likely just to further other plot points. An attack by a deadly rattlesnake is more exciting and cinematic that what really happened. And, given the setting outdoors in Arizona, which has more species of rattlesnakes than any other state in the country, they thought that the audience would not doubt that snakebites happen there all the time, even if they really don't. The screenwriters needed a temporary crisis to show the firefighters and their community helping each other, to show MacKenzie meeting the hospital nurse, and to show the bond between the firefighters, especially between McDonough and MacKenzie, who started out as enemies, then became good friends and roommates. The scene in the hospital, the scene with MacKenzie in the hospital room and the scene in the bar accomplished all that. Plus, they needed a reason for McDonough to be separated from his crew before the disaster and the truth - that he was recovering from the flu - wasn't heroic enough. No matter how realistic, a movie can't be boring.
Fortunately they did not use the standard snakebite cliche: a snake attacks and bites for no good reason, the victim kills the snake then either dies instantly or cuts the wound and sucks out the poison. This was the most realistic snake bite I've seen in a movie, especially the hospital scene. I don't know if a doctor would actually forgo using antivenin to use only antibiotics and morphine if the victim is not in critical condition, but it seems reasonable. Some people have a very bad reaction to the antivenin. Having the other firefighters hunt and kill the snake and cut off its tail is also realistic, as stupid as it is. People really do cut off and keep rattlesnake tails, which I once heard a snake hunter call "red-necking after we found a dead rattlesnake with the head and tail cut off. I also believed the saloon scene. It's completely in character with the other juvenile things we saw the firefighters do to each other as a way of bonding and letting off steam.
You can watch the snakebite scene and the first hospital scene on Youtube.