It's funny that some folks commenting here think that the voices were actually live (Foreigner1 and ted). I'm flattered that my dubbing and editing convinced you.

If you read the video description, you can see that the original video was taken by a brave soul who saved the beaver from being hit by shooing him off the road and keeping cars away. The voices were dubbed on later, comfortably indoors while the beaver presumably safely knawed on trees somewhere in the woods in his/her own habitat.