Bigfive,

I am going to guess for shock and knock down power. I have noticed with feral cats they seem highly tuned as far as their nervous systems go. They seem to be able to spring up and run pretty well even when very well hit, meaning right in the vitals.

I imagine cats like lions which are extremely strong will also have a lot of will power to attack even when shot.

A larger caliber may help prevent this with greater shock or a quicker death.