The ermine, scientifically known as Mustela erminea, is a small, sleek predator belonging to the Mustelidae family, which also includes badgers and otters. This highly active carnivore is often called the stoat or the short-tailed weasel, referencing its relatively short tail with a distinct black tip. It is widely distributed across the northern regions of North America, Europe, and Asia, inhabiting diverse environments from forests to tundra. A unique adaptation is its seasonal coat change, molting from a reddish-brown summer coat to a stark white winter coat for camouflage against the snow. This specialized body plan establishes the ermine as a formidable hunter whose survival depends entirely on its specialized diet.
The Core Diet of Small Mammals and Birds
The ermine’s diet is overwhelmingly carnivorous, relying on small, warm-blooded vertebrates to sustain its remarkably high metabolism. As a specialist predator, its survival hinges on the frequent consumption of nutrient-dense prey, primarily small rodents. Voles and mice are the staple food sources, making up the bulk of the ermine’s caloric intake across its range. Studies of stomach contents frequently show high percentages of shrews and deer mice, confirming their preference for the smallest mammals in their habitat.
Lagomorphs, such as young rabbits or hares, are also incorporated into the diet, despite often being significantly larger than the predator itself. The ermine’s slender body allows it to pursue prey directly into their burrows, making these tunnel-dwelling animals highly vulnerable. Beyond mammals, the ermine regularly preys upon ground-nesting birds, consuming both the adults and their eggs during the breeding season.
Hunting Techniques and Predatory Behavior
The ermine transitions from finding food to actively obtaining it through a set of specialized behaviors honed for speed and precision. Its long, slender body is perfectly suited for agility, allowing it to move in quick bursts and navigate dense undergrowth or rock piles. A primary strategy involves entering the underground tunnel systems of its rodent prey, where a smaller body size allows access to the narrowest vole runways. The ermine’s sensory focus is sharp, using its sense of smell to track rodents and its vision to locate fish or insects.
Once prey is secured, the ermine employs a characteristic mustelid killing method, dispatching the victim with a swift, targeted bite. This precise attack is delivered to the base of the skull, which severs the connection to the spine. In encounters with larger prey, such as a rabbit, the ermine may engage in a series of erratic movements known as the “dance of death.” This behavior can confuse and paralyze the victim with shock before the final attack.
This relentless predatory drive is also linked to a behavior known as surplus killing, where the ermine kills more than it can consume immediately. The excess food is not wasted, however, but is often cached in a special storage area within the den or under snow, ensuring a food supply for later consumption when hunting conditions are difficult.
Seasonal Variation and Opportunistic Feeding
While the ermine is a specialist predator focused on small mammals, its diet shows remarkable flexibility in response to environmental changes or prey scarcity. During periods when primary rodent populations are low, or in the winter when deep snow limits access, the ermine becomes highly opportunistic. Its diet may shift to include a variety of secondary food sources, demonstrating its adaptability to local conditions.
These secondary items include invertebrates such as insects, as well as amphibians like frogs and reptiles. In areas near water, ermines may also hunt and consume small fish. They are known to scavenge, taking advantage of carrion or scraps left behind by larger predators, particularly when fresh kills are difficult to obtain.
While meat is always the preferred energy source, the ermine has been observed to eat berries or other plant matter. This plant matter makes up only a minimal portion of its overall nutritional intake. The local habitat dictates the specific mix of these non-mammalian foods; for instance, ermines in forested landscapes may consume more tree squirrels and chipmunks than those in open fields.