"A death sentence for an animal acting on instinct when alternatives exist." - what are the alternatives? There are no suitable alternatives!
Us humans stuffed everything up when we introduced all these feral animals in the first place a long time ago...
The right and moral thing to do today would be to say 'sorry' to all the endangered and extinct animals and help them out by culling the feral invasive pest animals. i.e. pigs, goats, cats, foxes, deer, rabbits - the list goes on...