The film’s star tells 24Life about the demands of portraying female Marine and training with a canine partner.

When actress Kate Mara played the wife of a Marine in the thriller “Man Down,” she told the real-life Marine who was coaching her co-star Shia LaBeouf that she wanted one day to portray a female Marine. “He told me there are lots of great stories out there, you just have to find them because they don’t necessarily come to you—it’s sort of rare that they’re told [at all].”

A year later, she received a request from producers hoping to cast her in the film adaptation of the story of Megan Leavey, renowned for her service in the Marine Corps with her military combat dog, Rex, completing more than 100 life-saving missions at a time when women generally were not deployed to the front lines. After Leavey retired from active duty following injury from an IED explosion, her years-long efforts to adopt Rex made national headlines. “Megan Leavey,” starring Mara, Ramón Rodríguez, Tom Felton, Bradley Whitford, Edie Falco and Common, opens nationwide June 9—and 24Life had the chance to ask Mara about the physical and mental demands of the role.

24Life: In the film, you portray a female member of the Marine Corps, and one who is on active duty with a K9 unit. You’re also telling a real person’s story. What was it like to prepare for this role?

Kate Mara (KM): [Megan Leavey and I] met before we started shooting and just completely hit it off from day one. It felt like we knew each other forever…. She was actually in one of the boot camp scenes, screaming at me! I think she’s calling me a wimp or something.

We didn’t have a lot of time [to prepare], so it was jam-packed…. I was doing physical training with my awesome trainer here in LA, Ryan Farhoudi. We were obviously focusing on Marine boot camp stuff—lots of push-ups and sit-ups and sprinting. And we were boxing too, because that takes a lot of focus. I had this amazing sergeant major who worked with me on all the other stuff that a Marine learns, the weapons training and even how to put on your uniform, to make sure that I was really prepared.

Of course, the most important aspect was training with my dog. The real dog’s name was Varco and it was his first time doing a movie, and he wasn’t a trained military dog so he and I were learning together. At first I thought, “Oh, my gosh. I’m really surprised that they’ve chosen him.” I would’ve thought they would have chosen an ex-Marine dog or a dog that had experience in some way. I was so wrong because he was so amazing, and I think learning together really bonded us.

24Life: Was there anything about this particular role that surprised you?

KM: There’s a line in the movie—Marines say “[everything] goes down leash,” which means everything you’re feeling, the dog feels too. After like two weeks of shooting, Varco and I had to do one of the war scenes where there’s loud, fake explosives going off. And even though you know it’s fake and you’re safe, it’s still a little bit scary, and I had never really done anything like that specifically before. The dog’s leash is attached to your vest, which is also a little bit daunting, because if they decide to run, you’d better be ready to run or fall….

I remember being nervous, and I was sort of just squatting in the corner, getting ready to go. [Varco] was sitting next to me, and he turned to me and nuzzled his face in my arm and just kind of sat there looking at me. And I thought, “Oh my God, he knows. He knows what I’m feeling right now, and he’s telling me it’s okay.” And I instantly felt calmer, and like I wasn’t alone, and that I was safe, and he would have my back and I had his. I thought, “Oh. There’s a reason they say, ‘goes down leash,’ and I am feeling it right now.”

24Life: So was working with an animal actor not only a physical challenge, but a mental one?

KM: You can work with another human and just kind of fake it if there isn’t real chemistry. But with an animal, if there is no trust, it is really impossible to work with them. You have to be so vulnerable and open and very, very, very truthful when it comes to working with a dog. The trust has to be real, or it just doesn’t work.

24Life: Is there a message you’d like people to take away from the film?

KM: One of the things that I am most inspired by is the fact that the real Megan Leavey never gave up fighting for this thing that she believed in. We’re all going to go through something at some point in our lives where you need to fight a little bit for something, or someone, or a cause, or something that you believe in and something that you know is the right thing to do. I think it’s a beautiful story about never giving up hope.

24Life: Besides the specific preparation for this role, is there a ritual or routine that helps you prepare for a performance?

KM: It’s different with every role but in general, I have to work out on a daily basis for my mental well-being. I feel very differently when I don’t have time to do that. It’s like a form of meditation for me. Currently, I work privately with a trainer named Romi, every other day. We do Pilates on the reformer, and then we do ballet. I’m not experienced in ballet, and it takes such focus. It’s actually similar to boxing in a lot of ways. If you start thinking about something else, you cannot keep up. So it’s a great way to focus … I think it trains your brains in a lot of ways. That’s how I keep sane and also keep fit.

24Life: Performance can be grueling; is there something that you do for self-care, either during a production or in daily life?

KM: With “Megan Leavey,” I would go home and watch CNN, which is all politics, and this movie obviously is not a political movie but it made sense to do that. Usually I’ll unwind while watching something that makes me feel like I’m still sort of in that world. But when I’m done with the movie and I come home, it doesn’t take too much for me. If I’m with my family and my dogs, just being with them makes me feel like I can unwind easily.

Photo: Kate Mara stars as Megan Leavey in Gabriella Copperthwaite’s MEGAN LEAVEY, a Bleecker Street release. Michael Tacket/Bleecker Street