"You know, growing up I was always an animal lover," Duhamel explained to ET. "I was always a nature lover and I think as I've gotten older, it's become more about the planet and how precious and unique it is and some of the animals -- these beautiful animals we have on this planet. I think sometimes we take them for granted, and to think we're killing elephants and rhinos and tigers and all these animals for no good reason ... it just kind of ticks me off, so I try and do what I can to help."
"Our main objective here is just to get people to stop buying products from wildlife that are endangered," he continued. "There's no good reason why 33,000 elephants are killed a year or 73 million sharks. There's no reason to kill tigers -- tigers are not an aphrodisiac -- there's no reason to kill them. It's all of that -- it's elephants, it's rhinos, it's tigers, it's all these animals."
Clearly, Duhamel's passion for animals is stronger than ever.
"Imagine you're an alien coming from another planet to Earth, this amazing planet that sits in the middle of this galaxy with all this life, and if you think about some of these amazing animals from giraffes to tigers to, you know, everything -- the most amazing creatures here -- and I think sometimes we take that for granted," he said. "I think it's important that we prevent the extinction of an animal as beautiful as an elephant."
As for his film career, Duhamel is starring in the highly anticipated Love, Simon, which is about a 17-year-old closeted gay high school student who doesn't know who the anonymous classmate is that he's fallen for online. Duhamel and Jennifer Garner play Simon's parents, Jack and Emily Spier.
"I just saw it literally earlier this week," Duhamel said of the film, which is set to hit theaters next March. "And it's [directed by] Greg Berlanti, who I think is brilliant. I worked with him on a movie called Life as We Know It years ago, and he asked me to play the father of this kid who is closeted. He's in the closet and is terrified of coming out. And I think that that's, you know, a topical thing. But it's not a heavy movie. It's more of a comedy than it is anything else. And I just had a blast. I had a blast working with Jen."
"She's great. She's everything you would think," he continued about Garner. "She's a very sweet girl. ... very smart."
Duhamel later talked about the importance of the movie given the current political climate.
"I think it's very relevant," he said of Love, Simon. "Inclusion, I think, is important. And it doesn't matter who you are, what your sexual preference is, if you're male, female, whatever. You deserve the basic human respect. And I think that this movie really speaks to that. It speaks to this kid's courage. And my character is really about sort of changing his perspective on how he sees gay people."