The Least weasel (Mustela nivalis) lives deep in the Northeast Asian deciduous forest. It hunts day and night, aided by its sharp nails and long slender body. It is the world’s smallest carnivore. According to Blackfoot legend, this species is the bravest of all animals, a hunter that is bold out of proportion to its size. Modern scientists agree with this view, as every single feature of these graceful, lightning-fast little animals appears to be designed so that they are the perfect predator.
Diurnal animals are active during the daytime, with a period of sleeping or other inactivity at night. The timing of activity by an animal depends ...
A carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of a...
Scavengers are animals that consume dead organisms that have died from causes other than predation or have been killed by other predators. While sc...
Terrestrial animals are animals that live predominantly or entirely on land (e.g., cats, ants, snails), as compared with aquatic animals, which liv...
Altricial animals are those species whose newly hatched or born young are relatively immobile. They lack hair or down, are not able to obtain food ...
Among animals, viviparity is the development of the embryo inside the body of the parent. The term 'viviparity' and its adjective form 'viviparous'...
A burrow is a hole or tunnel excavated into the ground by an animal to create a space suitable for habitation, temporary refuge, or as a byproduct ...
A territory is a sociographical area that which an animal consistently defends against the conspecific competition (or, occasionally, against anima...
Pursuit predation is a form of predation in which predators actively give chase to their prey, either solitarily or as a group. Pursuit predators r...
Polygynandry is a mating system in which both males and females have multiple mating partners during a breeding season.
A dominance hierarchy (formerly and colloquially called a pecking order) is a type of social hierarchy that arises when members of animal social gr...
NoNot a migrant
Animals that do not make seasonal movements and stay in their native home ranges all year round are called not migrants or residents.
The Least weasel has a thin, greatly elongated, and extremely flexible body with a small, yet elongated, blunt-muzzled head that is no thicker than the neck. The eyes are small in relation to their head size and are bulging and dark colored. The legs and tail are relatively short, the latter constituting less than half the body length. The feet have sharp, dark-colored claws, and the soles are heavily-haired. The skull is, overall, similar to that of the stoat, but smaller, though the skulls of large male weasels tend to overlap in size with those of small female stoats. The winter fur is dense but short and closely fitting. In northern subspecies, the fur is soft and silky, but coarse in southern forms. The summer fur is very short, sparser, and rougher. The upper parts of the summer fur are dark but vary geographically from dark-tawny or dark chocolate to light pale tawny or sandy. The lower parts, including the lower jaw and inner sides of the legs, are white. There is often a brown spot at the corner of the mouth. The dividing line between the dark upper and light lower parts is usually straight but sometimes forms an irregular line. The tail is brown, and sometimes the tip is a little darker but it is never black. In the northern part of its range and at high altitudes, the Least weasel changes color in the winter, the coat becoming pure white and exhibiting a few black hairs in rare circumstances.
The Least weasel has a Holarctic circumboreal distribution, including much of North Africa and Europe, Asia, and regions of northern North America. Round in a variety of habitats, this animal favors plentiful prey and good cover, including woodland, grassland, mountains, sand dunes, urban areas, moors, and marshes.
Except for the breeding season, the Least weasels are solitary. They are territorial animals and form gender-based dominance hierarchies, with older males being dominant over juvenile males and females. Least weasels need to eat very regularly so that they do not starve to death, and often they are found foraging at any time of day. They commonly use food caching, as they often kill prey bigger than themselves, but only consume a few grams of meat for each meal. Caches are hidden around the den entrance, and latrine sites are as well. An individual scent marks around a den site with secretions from its anal glands. When startled or cornered, these glands release a bad-smelling fluid that will deter an antagonist. Least weasels also sometimes perform a “weasel war dance”, consisting of a series of twists and leaps, often accompanied by noises like barks, an arched back, stiff limbs, and erection of their caudal and dorsal hairs. Weasels of any age perform the dance, though it is more common in the younger ones, especially kits when playing with their siblings.
The least weasels are polygynandrous (promiscuous), with males and females mating numerous times with many partners. Males defend territories, usually against other males, but in the breeding season, they leave their territories to search for females. The breeding season is from March to June (though breeding can occur year-round). Following gestation of 34-37 days, a litter of 4-6 kits is born. Young are weaned at 4 weeks old and at 8 weeks old they are able to hunt, often going with their mother and hunting in 'gangs’. They are independent when they are 9-12 weeks of age and reach reproductive maturity when they are 3 to 4 months old.
Threats to this species include simplification and habitat loss. Agricultural changes in many areas have led to the reduction or loss of rough grasslands, prime habitat for Field voles, which is a primary source of food for this species. They are rarely seen and so are considered relatively rare. Population numbers vary with the abundance of prey, and they themselves are vulnerable to a range of predators, such as domestic dogs, cats, and foxes.
The Least weasel has a wide distribution and presumed large population, but no estimate of population size is available for this species. Currently, the Least weasel is classified as Least Concern (LC) and their numbers today remain stable.
Least weasels, being highly-skilled predators of rodents, play a vital role in initiating or maintaining cycles in rodent populations, an important part of the tundra ecosystem, where specialized predators, like Least weasels, play a role to keep lemming populations in check. In New Zealand, on the contrary, where the Least weasels have been introduced, bird species are negatively affected by predation by this species, especially Brown kiwis, which live on the ground.