I know it’s not possible for him to kill humans, but what about animals?
We do know the spiritual realm has influence over physical matter.
The devil of course, being of angelic nature , although fallen has not lost his spiritual nature anymore more then we who have a human nature cease to be human.
Since he is part of the spiritual realm… I guess the best answer would be … he is able to do whatever God permits of Him to do.
Jesus drove Legion into a herd of Swine which then all drowned.