The show doesn't have a particular environmental angle, nor does it have Selleck sounding like an ecological specialist. It's all about highlighting the nature of the creatures' daily adventures.
"The narration isn't particularly highfalutin stuff, it's more down-to-earth, and rather than talking down to the audience it's sharing the stories - stories that are quite compelling. When I saw the rough-cut footage, which they showed me before I did any narration, it's very involving.
"There are a lot of life-threatening situations covered and I find when I'm watching that I'm desperately rooting for the underdog. Like when a wolf attacks a young animal, that's sad, but then you see that the wolf has pups to feed and needs to survive.
"You get a great sense of the cycle of life. But it isn't all just dramatic situations, there's a certain amount of humour in nature and I think they did a good job of capturing that too."
Having spent time face-to-face with some of the animals in the series, Selleck is confident they've been captured in their true light.
"I remember I experienced the harrowing presence of the bison while shooting on film - they're bigger than you can imagine, and they can get angry, and run long distances. I think I actually chased a few in one scene. And I'm particularly fond of observing North American elk, they're such magnificent animals. But any show like this makes you want to experience more - I'd love to see the sheer formidable quality that a grizzly bear has."
He would love to get acquainted with New Zealand's milder wildlife too. He spent time in Auckland shooting Ike: Countdown to D-Day in 2003 and has always wanted to come back. "My great regret was that I didn't get to see much of New Zealand. I really wanted to go fishing, but six-day weeks don't give you much time off, so hopefully I'll get to come back some time."
Narrating a wildlife series was an refreshing change for Selleck from filming the drama series Blue Bloods (he's just finished shooting season four in New York, and season one is now screening in New Zealand), but he also found the two shows had plenty in common. "Some of the elements of drama that occur quite naturally in nature aren't that dissimilar to the kind of stuff we look for in a cop drama like Blue Bloods, except you don't have to create it. You need a lot of patience to find them, and to film them, but they don't have to create it."
Blue Bloods, a series centred on a family of cops, created by two of the writers for The Sopranos, drew Selleck back into police drama because of its strong characters and emphasis on family.
"When you really analyse Magnum, P.I., it was a character-drive piece, about four friends. And without putting them down, what I'm seeing these days on TV are procedurals, and though Blue Bloods has an element for police procedure, it's really about a family. It's about a family business even, like The Godfather was, only these guys are on the other side. The real drama in the show is within the family. Plus I liked the idea of playing this father figure.
"On American TV there are a lot of idiotic father figures, but in this case I get to play the patriarch of a family who's a widower, and really tries to do the right thing, and is reasonably smart. It's a great role."
Who: Tom Selleck
What: New series Wild Planet: North America, and Blue Bloods
Where and when: Wild Planet: North America begins on Tuesday at 8.30pm on TV One, Blue Bloods continues on TV3, 9.30pm on Saturdays.