This is a very interesting thread…
I have never professed to know anything about anything, but for my two cents worth… I feel the water provision policy must certainly have had an effect on Brownies, along with all the other species!
I don't think Brownies have ever been a common or prolific species in the park, not by a long shot. However, there are undeniable sporadic reports of sightings through the years. They have probably always been nomadic vagrants to or through KNP, only occasionally establishing small populations when conditions were favorable?
It is no secret that they do well in dry and extremely dry habitats.
I am of the opinion (and I stand to be corrected) that they are powerfull predators, but timid, usually not willing to stand up to lions and spotties. Yes, you hear the odd story of "someone once told me they saw 17 brownies chase 4 lionesses off their kill and….", but those stories are very few and far between. In general I believe brownies forage singularly and for their size and strength, they could command a lot more respect, but are usually timid predators.
Most of the early sighting records are from the early decades, the 30's, 40's, 50's, even the 60's. The water provision policy really only started in earnest in the drought years of the 60's. Prior to this there were but a few boreholes around. From '61 to '76 the majority of the boreholes were implemented. This increased the number of water dependent game species in the dry areas, which in turn attracted more lions and spotties to these areas, increasing pressure and competition for the brownies. With the increased water and increased large predator competition, it is no wonder the brownies are around even less now then they were 70 years ago.
That is not to say they are not here, I believe they are still nomadic vagrants, and they are still seen very occasionally in the park. But hopefully with the revised water policy of 1997 closing down 200 odd artificial water points, and the possibility of a drought this year (which would be the first decent drought in 20 years since the decision to start closing waterholes), the bush will be returning to a more natural state and may be moving towards more suitable habitat for brownies once again.
We may start seeing a few more of them yet…