Long and Short-tailed Weasels, Mustela frenata and Mustela erminea
Common Names: Short-tailed: Stoat, or Ermine
Species: Mustela frenata and Mustela erminea
General Description: Members of the Mustelidae family are distinguished by elongated bodies, and short legs. Most weasels have a fur coat of chestnut to cinnamon brown, with a yellow/white underside and feet. In northern regions, the weasels will grow a winter coat of white hair. The molting of the summer coat has been shown to occur gradually, dictated by the length of daylight. Some species in the Arctic are white year round. Both Mustela frenata and Mustela erminea have a unique black-tipped tail, present with both seasonal coats. Studies have proven that the winter white coat is genetically linked. Northern species have been trapped and relocated in southern areas, and they will still molt the summer coat despite the lack of environmental necessity or advantage. Long-tailed Weasels measure 280-550 mm in length, and range from 85-267 g. The Short-tailed are smaller, with a average length of 42-90 mm, and weight of 45-182 g. In general, males are double the size of the females. Other noticable characterisitcs include 5 toed feet, and round black eyes with vivid green “eyeshine”. Weasels also have a several presence indicators. From scent marks left in a Mustelidae territory, visitors can determine sex, dominance status and reproductive condition. The scat (fecal matter) is distinctive for each species, as well as tracks found in snow and mud.
Geographical Distribution and Habitat Requirements: Mustela frenata and Mustela erminea are both quite versitile in many habitats. They have been found to live in open woodlands, brushy areas, grasslands, wetlands and farmland. When possible, they prefer to be in a location with a nearby water source. Some species can easily survive in the snowy north, by living under the insulating snow. They hunt through rodent runways, as well as sleep and breed in rodent nests. It has been suggested, that Mustelia may be the most widespread carnivore in the western hemisphere. They range from southern Canada (including all of New Brunswick), most of the USA, and down through to Bolivia. Mustela frenata is limited to the North American continent, while Mustela erminea is also distributed throughout southern Europe and Asia. The diversity of the weasels habitat is closely related to their capability of changing sources of nutrition.
General Biology: Weasels are adapted to ground life with their short legs and long bodies. However, they also have a very flexible spinal column, which allows them to be exceptionally agile. They are good diggers, swimmers and divers (Mustela frenata are less adept swimmers than Stoats). Weasels consume mice, voles, rabbits, chipmunks, shrews, rats, frogs, lizards, snakes,birds, poultry and occasionally insects and earthworms. They seem to prefer larger species, as mice and voles are thier primary targets. Mustela frenata and Mustela erminea hunt in rapid dashes, almost like a zig zag fashion, and then pounce on their prey with all four feet. They quickly bite through the neck, at the base of the skull. They lick the blood from the carcass first, then consume the head and thorax. Weasels are known as a major nuisance since they will kill more than they can consume, and store any leftovers. Weasels were first thought to be nocturnal, however they are actually diurnal, especially since much of their prey is not noctural. It is also interesting to note, that within 24 hours, the Mustelides are only active in 20 minute to three hour time periods. The total life span for Mustela is six to eight years. Males are sexually mature in their second year, while females are able to be breed in the June-July mating season of their first year. The females will stay in heat during the breeding season for weeks, until breeding occurs. Very few species of Mustelia undergo the unique process of delayed implantation as both Mustela frenata and Mustela erminea do. After fertilization, the egg develops for approximately two weeks, then stops. Implantation of the egg in the uterus is delayed for nine to ten months. Implantation occurs the following spring, and active gestation continues for about a month. The total gestation period for these Mustelides averages between 205 – 314 days. A litter of four to nine are born blind, with fine hair in April, in a protected den. Their eyes will open approximately 35 days later. The weasel’s den has many entrances, and they will have many nests in their home range. Another interesting characterisitc about weasels, are it’s distinctive noises. It will purr when content, and also has different ranges of chatters, hisses, grunts and shrill calls.
Conservation: Mustela frenata and Mustela erminea both have stable conservation status. Main predators include hawks, owls, other carinvores, and snakes. Due to their diverse habitat, and varied food sources, they have been able to securely exist in contemporary environments. In the past, weasels have been trapped by humans, due to killing of poultry stocks, or for their furs (mainly the long-tailed weasel for it’s long winter pelt). In 1980, 80 000 – 125 000 furs (of Mustela frenata and Mustela erminea) were traded in North America for $115 000 – $125 000. More recently, only 300 – 500 stoat pelts were traded.