Continuing that rabbit trail...Actually, that would be Darwin, not Pavlov unless we're talking about non-lethality. I've also noticed a similar effect.....there just isn't as much road kill as there was when I was a kid.
Perhaps that's the effect of things being less rural now, but I don't think so...even when I visit EBF Maine. When I was a kid in NH there was a clobbered chipmunk or squirrel speedbump every quarter mile. I think over the many generations, only the ones that avoid the traffic (or look both ways or jump up to hit the walk button) survive.
I wasn't thinking so much about survivors being more wary, as I was of bystanders (fliers?)learning to avoid the whine after smelling the burnt remains of thier late buzz-buddies.
On the road-kill - living in a rural desert area for the past 25+ years, I can absolutely state that road-kill events have increased greatly - while visible road-kill has diminished. Our local predator population has exploded - with the main visible culprits being Ravens (Corvus corax) and Coyotes (Canis latrans). Our hawks, vultures, and other predators - mammals, avian, insect, etc - have definitely taken advantage of the bountiful windfall of food provided by the increased road traffic. A squirrel or rabbit killed on the tarmac won't even be cold, before it is snatched up!