A brown bear mother and her cubs come within feet of ecologist and bear biologist Chris Morgan. Watch video from Bears of the Last Frontier: City of Bears.

The scent that a female brown bear gives off helps the male determine if she is receptive to mating. Watch video from Bears of the Last Frontier: City of Bears.

It’s finally here — time for us to share our incredible Alaskan adventure with the world through Bears of the Last Frontier. It has been quite the journey. The film has been nearly two years in the making, and for both of us it has become an unforgettable part of our lives

Delayed implantation, hibernation, and everything else you'd want to know about Ursus arctos.

Lichen survive outer space (and what that might say about how life on earth began), genetic research suggests dolphins are second in intelligence to modern humans, new dinosaur bird ancestor discovered in Argentina, and more of this week's top nature stories.

The wild stallion saga continues. Watch the full episode of Cloud: Challenge of the Stallions online.

(Premieres Sunday, October 25) It's springtime, and competition among stallions is fierce. Who will emerge victorious?

Lonesome George, a Pinta Island subspecies of Galápagos giant tortoise believed to be the last of his kind, died on Sunday, June 24.

This week's dirt: new study suggests a warmer, greener Antarctica 20 million years ago, gorilla populations start to rebound after 2004 ebola outbreak, sponge DNA may give us new insight into our central nervous system, new research shows that goat moms know their kids' voices, and more.

A practical guide to billfish, a group of predatory fish that includes marlin, swordfish, sailfish and spearfish that are best known for their prominent bills.