@cataxion wrote:
This is NOT an episode of Nature: it is an episode of Nova!

Not according to the Nature website:

https://www.pbs.org/wnet/nature/serengeti-rules-dhbtnm/19906/

I've listed this episode as a "Special" because the numbering scheme does not appear to match the sequence on 48 Hours' web site, and this episode was omitted. I'm hoping to figure out how to put it in correct sequence, or that someone else will do so. The air date I have included IS correct. Sorry for any confusion!

-- Sam

Some guides show this as Season 4, Episode 20, which is the sequence in which it aired. Nat Geo's site now shows it as a special episode, but I suspect this is because Professor Hawking passed away soon after this episode aired.

The first half of this show is indeed "Stranger Signals from Alien Planets." But the second half seems to be an episode of "Strip the Cosmos" called "Alien Worlds." (The bump-out and bump-in for commercial ads displays "Strip the Cosmos.)