the hunting behavior of wild weasels is very difficult to observe. You can go every day to an area you know to be inhabited by weasels, and never see one. Modern tools such as radio telemetry have reduced that problem to some extent; now researchers can find radio-collared weasels in their rest sites, and have a better chance of watching them hunt. Bogumila Jgdrzejwska and Wlodzmierz Jgdrzejwski (1998) watched wild common weasels hunting in the Bialowieza Forest in Poland during early evening. When rodent populations were high, they followed their radio-tagged weasels as they systematically searched the forest floor along logs, under fallen branches, down holes along roots, and up trees into holes and crevices. Without access to that give-away radio signal, few of us can be so lucky.
On the other hand, weasels are so small, as carnivores go, that it is possible to set up fairly natural conditions for them in captivity, where observations are easier to control. By providing weasels with wild-caught prey in a large enclosure furnished with grass and trees, and watching through a window, one can learn much about their hunting and killing behavior. Another tactic that works well in cold climates is to deduce the hunting tactics of weasels by reading tracks and signs in snow. Skilled woodsmen such as Ernest Thompson Seton (1926) could read whole stories from snow tracks. Even chance encounters with wild weasels are important and can give fascinating glimpses of natural behavior, but they have also spawned a whole literature of unlikely stories that are impossible to interpret.
Being a predator is a risky profession. Some types of prey are easy to find but dangerous to attack. For example, rabbits are much bigger than even the big weasels, and in the open, a rabbit is formidable prey for a small hunter. An enraged doe rabbit with young to protect has been seen to chase and kick a stoat halfway across a paddock. Other prey are also well protected in different ways— for example, the spines of a live hedgehog appear to be a completely effective defense. Small predators dealing with prey that are well defended or larger than themselves must choose and approach their targets carefully.
By contrast, other kinds of prey, including most of those sought by weasels, are easy to kill but widely dispersed and well hidden. Most voles offer little physical resistance once found by a weasel, but the weasel runs a high risk of failing to find enough voles each day to fulfill its needs. If that happens often enough, the weasel dies. Death is the ultimate penalty for predators that misjudge the hazards of hunting—not merely the death of their own bodies, for that is inevitable sooner or later, but the worse failure of dying before raising any young.
There are three main kinds of predators, which balance the risks of hunting in different ways. Pack-hunters, such as wolves and African lions, live in groups that depend on, and often live within sight of, large and formidable prey that are more easily found than killed. Ambushers, like mountain lions and leopards, patiently lie in wait for a suitable prey to pass by. Weasels are neither sociable nor patient. They are active, solitary searchers that specialize in exploring every likely place for small and vulnerable prey, especially rodents, that are more easily killed than found. They hunt alone, with restless energy and fierce concentration. They are adaptable and intelligent, and tailor their methods according to their targets and their opportunities.
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