Even among the reasonably ritzy clientele of a swish Dublin hotel, there's little point in playing Spot the Movie Star when Kellan Lutz is in the house. Everything about the 29-year-old might, in fact, be prefaced with the word "Hollywood": he's got the Hollywood clothes, the Hollywood looks, the Hollywood orthodontics, the Hollywood abs (in fact, you can find the Kellan Lutz workout in Men's Health magazine).

Lutz is a dreamboat of the old school, so it's no accident that the Twilight saga star has become a hit on the swords and sandals circuit: he was Poseidon in Immortals (2011) and lately took a bow for the title role in The Legend of Hercules. Now, he's in cinemas as Tarzan, in a new animated adventure based on Edgar Rice Burroughs's 1914 standard. "I grew up in the Midwest, so Tarzan was always one of my favourite heroes," he says. "It fits with what I'm passionate about. I think every parent must have given their boy that book. Or you came across it in a movie. It's timeless."

Animal rights activism
For Lutz, a Christian and animal-rights activist, Tarzan has gifted an opportunity to campaign on behalf of Ape Action Africa, a charity that works to protect endangered primates in Cameroon.

“We’re trying to stop the killing of apes for meat,” he says. “It’s being eaten as a delicacy. There’s a belief that the meat gives strength. Then the children are taken and sold as pets. They eventually die without their mothers. We’re also trying to stop the deforestation that comes with the hunting.”

He is aware that advocacy on behalf of animals can be a double-edged sword. Any positive publicity from his work with primates could be countered by his association with Peta, an organisation that is no stranger to controversy.

“I don’t think people should wear fur,” says Lutz. “I don’t wear it. I try not to judge someone who has that preference. But if you have a choice, then why? I’m an advocate for any animal that is treated inhumanely.”

His beliefs, he suspects, can be traced to his North Dakota origins. He is the middle child in a family comprising six brothers and one sister. Lutz refers repeatedly to the solitude and wide-open spaces that shaped him, and he prefers hiking, camping and skydiving to the red carpet.

“I was very much alone. So the animals became my friends. We owned a farm. And I became almost like an animal whisperer. Cats would come to me. Hens. Cows. I’m a feeler, I guess. So when you have alone time, you create your own fantasy worlds.”

An outdoorsy type, Lutz had no great interest in movies, and was studying chemical engineering at California's Chapman University when he was snapped up as the cover star for an Abercrombie & Fitch catalogue. By 2005, he had landed a recurring role on Michael Patrick King's The Comeback. Teen movies soon beckoned, notably Stick It, Prom Night and the 2010 Nightmare on Elm Street reboot.

“I didn’t even know who Brad Pitt was,” says Lutz. “I started acting at 18 at college. But even then I didn’t take theatre or think to study acting. I thought it was like Nascar. You had to buy your way in. It sounds like I was ignorant. But it just wasn’t something I cared about. It wasn’t in my sights. But then doors opened up.”

Those doors included Catherine Hardwicke's Twilight (2008), a film that quickly snowballed into a billion-dollar franchise and bestowed instant recognisability on Lutz. Over four films, the actor's portrayal of Emmett Cullen became a consensus favourite for Twi-hards representing rival Teams Edward and Jacob.

"I read the script and I wasn't all that turned on by it," he says. "The vampire movies I like are a little bit gritty, like 30 Days of Night. And Twilight seemed a bit chick-flicky. We didn't have fangs or anything. But I did love my character."

When did he realise that it was quite the thing? “It took a little while. Once I got the role Ashley Greene asked me if I had read the books. And I said, ‘What books?’ It was only when fans started turning up to watch us shooting – I mean, we’re out in the deepest woods, out in the sticks outside Portland – and they’re turning up. And then I start to think that we might end up doing a sequel. And then there’s the first premiere. I’ll never forget it. Extreme name-yelling. Girls crying. Paparazzi everywhere. It was a lot to process.”

Lutz will be taking his leave from screaming girls in favour of the shouty boys of The Expendables 3. It's lucky he has had practice with all those brothers. How else could he have coped in a cast that features Sylvester Stallone, Jason Statham, Jet Li, Dolph Lundgren, Randy Couture, Terry Crews, Arnold Schwarzenegger, Wesley Snipes, Antonio Banderas, Mel Gibson, Harrison Ford, and Kelsey Grammer? That's a lot of alpha male for one set.

“Yep. A lot of testosterone. And honestly: no egos at all. That was awesome. You’re loading up guns and shooting alongside all these icons. To hang out with them and to discover they’re badasses off screen was even better.”

Tarzan 3D is out now