Mustelid Killing Behaviours
by Bob Church
Thought I would share what I know about mustelid killing behaviours, having watched more than a thousand "kills" by various mustelids.
Mustelids are a wildly diverse group, which means they have a number of prey-killing strategies, so I will limit the comments to those of the subgenus Vison, which includes mink, weasels, polecats, and domesticated ferrets, (but much of what I will write about can be applied to martens, fishers, sables, etc.) Hunting behaviours in this group are remarkably similar, so what is generally said of stoats can be applied to polecats, and that of polecats to ferrets, etc. They are all small predators that eat a variety of creatures, ranging from insects to fish and from amphibians and birds to small mammals.
Because of their small size, they are in constant danger of the prey turning and hurting them. With rabbits and rats, this is especially dangerous, and there are many reports of both rats and rabbits seriously injuring and even killing stoats, polecats, and ferrets. As a result, they have developed a wide range of hunting strategies to minimize the risk, so a particular hunting method is correlated to prey size and species. However, there are some generalisations that hold true.
The most common method of killing (by far) is by crushing the base of the skull using a forceful bite. (Because of the biomechanical construction of the mustelid jaw, their bite is particularly forceful. One biomechcanical author wrote that he thought that pound-per-pound, the mustelids had the strongest bite in the class mammalia. While I have never been bitten by a hyena, which can crush elephant bones in their jaws, I have been bitten by a number of mustelids--like mink--and can vouch for the nastiness of the experience. I would hate to think what they could do if they were the size of large dogs.) The second most common method is by crushing the first or second cervical vertebra in the neck which attach to the base of the skull. Both methods either crush the cerebellum and/or pons, destroy the spinal cord, or disrupt the flow of blood to the brain--making death instantaneous. This is very important for such a small predator so they not only conserve energy making the kill, but also vastly reduce the chance of being injured themselves.
For animals smaller than themselves, usually the mustelid does a "spring and bite" or the much-discussed "torpedo run." The rush in and bite method is very effective for voles and mice, which the pounce and bite seems to work better for insects and amphibians which aren't much of a danger. For more dangerous animals about their size or larger (like rats and rabbits), a different set of tactics is employed. Normally, the mustelid will attack the nose and face of the prey animal, biting until the prey is weakened from lack of blood, goes into shock, is blinded, or is otherwise unable to defend itself. Once this takes place, the bite to the back of the head is employed, and the animal is quickly dispatched.
Often during these dangerous encounters, the mustelid will bite and roll, or bite and shake the prey. The roll method, especially with a facial bite, is very destructive, and quickly renders the prey unable to defend itself. The shake appears to increase the injury caused by the bite, crushing bone, severing tissue, and increases bleeding. While these techniques have been reported being used on prey smaller than themselves, it is usually reserved for the larger prey, and seems designed to increase the success of the hunt while decreasing the chance of injury.
The two most commonly consumed portions of the mammalian prey includes the brains and the hindquarters, while in birds it is the brains and breasts, but these represent disturbed kills. Usually the mustelid will carry the prey to the "hidey hole" for later consumption, and little is left uneaten. If surplus animals are available, the mustelid will kill as many as possible, and store the uneaten prey in safe locations, but this is relatively rare in the wild--most commonly seen in situations where the mustelid takes advantage of human caging practices (hen-houses, duck ponds, etc). These behaviours are designed to maximise nutrition; one never knows when a larger predator will steal your food or try to make you lunch only to eat yours after you make an escape.
As can be easily seen, the behaviours as described are mirrored in the ferret's play, sex and dominance behaviours. Stashing toys, neck bites and rolls, torpedo runs, and reaction to high pitched sounds all betray a predatory origin for a domestic pet whose kin are among the oldest and most successful mammalian predators that ever lived. What you are seeing is unhoned instinctual responses, and alone will not necessarily insure survival in the wild. Mustelids must be taught how to hunt and what to eat, and so have a long period of learning at their mother's side, up to 1/4th or more of their total lifespan, compared to 1/8th to 1/10th (or less) for dogs and cats.
I once had a professor that said cats were never domesticated, they just pretended to be for the free chow. Dogs were just too dumb to know the difference. What has this to do with the prior discussion? Nothing...I just wanted something witty to end on after such a gruesome discussion.