A cougar is similar in size to a leopard, and in Africa they are considered very difficult to hunt (same thing in India, where man eating leopards are considered worse than tigers). The thing about them is this - and I will delete the fact that they are fast, cunning and sharp of tooth and claw. The thing is they have huge lungs, and their blood is significantly more oxygenated than that of a human. Big game hunters (and leopards are considered big game, which is why it's interesting to me that the hunters consider cougar human-equivalents) have shot right through leopard hearts, and the leopard still has enough moxie to finish the charge and mail them. Big game hunters would often wear 'leopard armor' (a metal or heavy leather neck protector) when tracking leopard spoor in the bush, because at close quarters the brain and blood would be sufficiently oxygenated to finish a charge even when the heart was shredded.
What does that have to do with Cougars? Similar sized cat, and more importantly, similarly oxygenated blood that is at a level no human ever alive would have. Which is why the cat can be shot, mess up your dogs, and then run off to die. A bigger bullet can do a better job than a 9mm (same reason people hunting leopards never use pistols), but my point is simply that no cat (even house cats) are a comparison to humans no matter how soft the skin is.
Dogs and boars are another. I've heard about how 'measly' 9mm will at times shatter on their skulls. Thing is their skulls are very different from that of a human, and depending on shot angle the round can be deflected.
Anyway, for most human beings, a pistol of normal barrel length shooting modern hollow points in 9mm, will be more than enough to ensure they give proper attention. As for those few who seem to shrug 9mm bullets (and we are talking HPs and not FMJs, so no Moro Moro tribesmen), they would similarly shrug off .45s (there are interesting stories of people who have soaked up multiple bullet hits, some eventually dying later and others making it, including .45s)
A modern hollow point fired by someone who can hit the broad side of a barn more times than not is 100% effective is virtually every situation.
Would you personally carry a 9mm semi as your brown bear deterrent device in the bush, or would you go with a larger calibre?
I’m not sure about the cougar and leopard comparison. North American hunters seem to think cougar is easier to kill than a black bear so... anyway i think most people would rather deal with a black bear than a leopard.
My thinking on this has been heavily influenced by an article reprint posted in this discussion on handguns for bear and cougar:
look for a long post by JJHACK, title “Hunting bears with handguns”
He has a section on police wanting to take treed bears with their duty guns, and the relative performance of the different calibers.
Now a bear is not soft skinned like a cougar (cougar with carhartt coat?) but the author makes a comparison between a 300 pound treed bear full of adrenaline and a 300 pound criminal hopped up on dope.
I’m not sure how exact the comparison between a 300 pound treed bear and a 300 pound male wearing heavy clothing and hopped up on dope. But I think it is worth thinking about.