Just watched a documentary (more precisely a film) on Discovery Channel (209) last Sunday night –"Grizzly Man", followed by "Diary of the Grizzly Man" (which recorded what Timothy Treadwell's friends thought about the film).  There have been a lot of controversies around the film and the life of Timothy Treadwell since the release of his story in 2005.  It's not just a documentary or a heroic record of an ecologist (Tim was not really an ecologist at all) but a story about a man who discovered the meaning and direction of his life after spending all the chaotic years indulging in drugs and alcohol.  I don't know when it'll be shown again (you can check the timetable) but it's worthwhile to take a look.
For more information about "Grizzly Man":  http://en.wikipedia.org/wiki/Grizzly_Man

P.S.  Though the story is centered on grizzly bears and wolves, it contains heart-breaking scenes which therefore is not so suitable for young children (or PG is recommended).