Spaniel,

I think that the DNA testing (and other tests) on at least one of the ones killed indicated that it had originated out west in the Black Hills area, i think. As you stated, I think that the only time you can prove there is a breeding population of any kind will be when there are reports of very young panthers or pregnant females. When only a couple mature ones are turning up then the assuption will be that they are wandering long distances in search of mates. But you don't know if they are successful until there is proof of young being born in a given area.

They kind of remind me of what i have read about black bears. You can have long periods where the only sign of them is the occasionally young male passing thru an area in search of a mate. You dont get any really good signs until you end up with mated pairs and young that remain in the general area and that can take years or decades.