It can sometimes be a tricky adjustment, introducing a newborn to your furry family, but Josh Duhamel's
dog Zoe has 4½-month-old son Axl all figured out.
"It's really funny now to see them both," Duhamel told PEOPLE at the Sundance Film Festival on Monday. "He's fascinated by her ... [Axl is] really starting to pay a lot of attention to her and [the dog] sees him strictly as a potential ball thrower."
Watching their budding friendship take shape has been "awesome," says the actor, who adds, "[Zoe] knew how much we loved this new little addition to the family and she knew that inherently."
"It's all been good. She's a very sweet dog," Duhamel continues, "[and] she knows pretty soon he's going to be able to play with her."
Pups Zoe and Milo
are the reason the star, who is married to singer Fergie
, stepped out in Park City, Utah,
this week, where he kicked off the Pedigree See What Good Food Can Do
campaign. The initiative celebrates the stories of shelter dogs who have found loving forever homes. Every time dog lovers share their tales of what their dog means to them – using the hashtag #DogTales on Facebook, Twitter or Instagram – the pet food company will donate a bowl of food to a shelter in need.
For anyone in the market for a canine companion, Duhamel, 42, encourages adopting from a shelter. "We bought [Zoe] and she's a great little dog," he says. "And then we rescued Milo about a year or two later and for me there was just a noticeable difference because I think these dogs really appreciate their second chance. They know what the alternative is like, so I just felt like he was extremely appreciative of us."