OK...in 40 years....have squirrels become armor plated, x-men type mutants, or evolved into some hard shelled super critter?
OK...just for the youngsters and the challenged members: NO.
Bought an HW 35E and less than a year later wife bought a FWB 124D. Those where the "hot stuff" arigunes of 1978-1979.
Squirrels, rats, rabbits, pest birds, (OK..quite a few eathing birds like Dovers/Quail too), a trip to Oregon for digger squirrels, and a couple of woodshucks in West Virginia.
So...yeah....it's not the critters that have gotten tougher (OK...I'll give you the explsion of feral pigs in the last couple of decades)....but the shooters less relaint on intersection of the good bits with the pellet.