The stoat, known scientifically as Mustela erminea, is a small, agile carnivore belonging to the Mustelidae family, which also includes weasels and ferrets. This predator is also commonly referred to as the short-tailed weasel or, when in its white winter coat, the ermine. The species has a wide distribution across the Holarctic region, encompassing northern areas of Eurasia and North America, demonstrating its adaptability to diverse cold and temperate environments. The stoat possesses a high metabolic rate, meaning it burns energy quickly and requires a nearly constant supply of food to survive. This physiological need drives its relentless and predatory hunting behavior.
Primary Mammalian Prey
The foundation of the stoat’s diet is composed of small mammals, which are necessary to meet its substantial daily energy requirements. Rodents such as voles, mice, shrews, and hamsters are consistently targeted and form the bulk of its consumed biomass in many regions. In Great Britain, however, lagomorphs—specifically the European rabbit—can constitute a significant portion of the diet, especially for larger male stoats. The stoat’s hunting ambition often exceeds its size, as it regularly preys on animals considerably larger than itself. It can take down adult rats and young rabbits or hares that may be five times its own weight. Female stoats tend to eat a higher proportion of smaller rodents, while males consume more of the larger lagomorphs, reflecting the male’s greater overall food requirements.
Opportunistic and Seasonal Foraging
The stoat is an opportunistic hunter that supplements its diet with a wide variety of secondary prey based on availability and season. During the nesting season, ground-nesting birds, their eggs, and fledglings become a more frequent part of the menu. The stoat is known to climb trees and raid nest boxes to access these protein-rich meals. Invertebrates, particularly large insects, also appear frequently in gut content analysis, although they contribute less to the total consumed biomass than mammals. Amphibians, reptiles like lizards, and occasionally fish are consumed when mammalian prey is scarce. When food resources become low, the stoat may turn to plant matter, such as berries or fruit, and has also been known to consume carrion.
Hunting Techniques and Predatory Behavior
The stoat’s hunting success is driven by its exceptional agility, speed, and persistence, allowing it to pursue prey both above and below ground. Its long, slender body is perfectly adapted for following rodents and lagomorphs deep into their narrow, underground burrow systems. The stoat will check virtually every crevice and hole in its path during a hunting excursion. When a kill is made, the stoat employs a specialized technique, often dispatching its prey with a swift, lethal bite to the back of the neck or the skull. This cranial bite allows it to overcome animals much larger than itself. The stoat’s hunting repertoire sometimes includes a peculiar, acrobatic movement known as the “weasel war dance,” which is thought to confuse or mesmerize potential prey before the final attack. Stoats also cache surplus kills underground to provide a reserve for times of scarcity.
Ecological Impact of Stoat Predation
The stoat serves as a natural regulator of small mammal populations within its native Holarctic ecosystems. By preying heavily on rodents and lagomorphs, it exerts a top-down pressure that helps maintain a balance in the ecosystem’s structure. The population density of stoats often fluctuates directly with the abundance of their primary prey species. However, the consequences of stoat predation are dramatically different in regions where it has been introduced, such as New Zealand. Stoats were released there in the late 19th century to control rabbit populations, but they quickly became a major threat to native wildlife. Native New Zealand bird species, particularly those that are flightless or ground-nesting, had not co-evolved with mammalian predators and are highly vulnerable to the stoat’s predatory skill. The resulting severe decline in species like the kiwi and kakapo has led to the stoat being nominated as one of the world’s most damaging invasive species.