The whole thing with birdshot is the range.
As I said, if you said this happened at 20 feet, I would have guaranteed a dead cat with number 8 birdshot.
I have seen it too many times on humans.
But I never saw anyone shot at 30 feet.
I did have a buddy get shot with number 6 crow shot at 35 yards. He took 52 pellets in the back, neck, and side of the face. Those pellets penetrated about one inch.
If I had a shotgun, I would go right out and do a test at 30 feet with some birdshot. I would get an old leather boot, stick a foot long one by four in there to simulate bone, and see what a load of number 8s would do.
I bet a dollar it would blow right through the leather, blow a big hole in the board, and blow out the back side of the boot.
ie, dead cougar.