Cats Hunting Instinct
Quite often, those who love cats also love birds and small mammals and can't accept that their sweet cat is a ruthless hunter. Even the best fed cat won't miss a chance to hunt mice and birds; it is an instinct with deep roots and, in absence of real prey, a cat will focus its natural instincts on substitute prey, such asor hanging string.
What brings out the cats hunting instinct is movement, not hunger. Alerted by the smallest movement in the grass, the cat stalks its victim, it crouches with its eyes fixed and ears alert. When in reach of its victim, it crouches back, leans on its hind legs and then launches itself onto its prey. The cat's instinct is to protect itself from harm; a rat bite can be lethal. This is why it bites the victims head or throws disorienting hits in the air. If the victim tries to escape, movement unleashes the stalking response once again.
It seems to us that the cat is cruel by the way it "tortures" its prey. It frees it and catches it before giving it that last lethal bite. Whereas, in reality this is just a sign that it is an incompetent hunter. It has a hunting instinct, but actually finishing the job (by biting the cervix to finally break the spinal cord and give it an instant death) is a skill that has be practiced. Cats that are raised by mothers that are not used to hunting, don't learn this skill and when they finally catch their prey they are uncertain of what to do with it.
Note: Towser was a female "employed" as a mouse hunter in a whisky distillery in Scotland until her death in 1987. During her working life she killed more than 29,000 mice, an average of three deaths a day.