You have a point, and my statement is probably narrow minded, however I based that statement on the sheer number of Thamnophis that get run over by mowers, chopped up by the misinformed irrational phobia cases, road kills, etc.. Yet there always seems to be plenty of garter snakes in the areas that support them.

I'm not going to lose any sleep because some crow or raven does not get his liver treats either.

I can't speak for heavily urbanized areas, but the rural farmland areas that are scattered all over America seem to be alive with garter snakes.

You even said yourself that one possible reason garter snakes can tolerate group housing is because they are one of the most densely populated species in existence.

Something like a drought wiping out all the food or an extremely cold winter pushing the frostline down an extra couple feet is surely going to have a far greater impact on the snakes than a person or two bringing a specimen into the house and keeping it properly.