Predators Of Weasels

Tame weasels of any species, well settled in captivity, can live up to 10 years. Why do most wild weasels achieve only a tenth or less of their potential life span The most obvious explanation, considering that weasels are obligate predators dependent on wildly variable food supplies, is shortage of food, but there are others. Stoats and longtails are often killed on the road, especially males in spring (Buchanan 1987 Sleeman 1988a). The active lifestyle of weasels and their insatiable...

Protection For Weasels

After centuries of killing predators to protect human interests, concern for predatory animals as individuals and for their own sake is a very recent idea in Europe (Reynolds & Tapper 1996). European settlers carried their cultural attitudes to North America, including the selective destruction of predators to favor game, although that policy was on its way out in the national parks of the United States by the 1930s (Dunlap 1999). Weasels are small and subject to little rancorous debate...

Energy Equations And A Weasels Choice Of Prey

The food eaten by a hunting animal is determined largely by three things what there is to hunt, what the hunter can catch, and whether the chase is worthwhile. The best kind of prey for a hunter is one that is easy to find, is easy to kill, provides a much greater return in energy than the hunter spent in getting hold of it, and is always available. These are the reasons that, for weasels, the ideal prey are voles, mice, and lemmings. They make clear runways and burrows leading straight to...

Sexual Dimorphism

Male weasels of all species are substantially larger than females (see Table 4.1 Figure 14.1). The reason for this difference was at first considered to have something to do with food (Brown & Lasiewski 1972). Because the two sexes are so different in size, they tend to eat different things so, the argument ran, the difference must have arisen so that each could avoid trespassing on the other's food supplies. In times of food shortage, this trick might be valuable to both. Indeed, the...

The Problem of Black Tipped Tails

One of the curious quirks of research, and the salvation of many a graduate student, is that it is possible to design a study to ask one question and then be led to a valid answer to a different question. Powell's convictions about the effect of raptor predation on the numbers of weasels in ecological time stimulated him to design a series of simple, elegant experiments with trained red-tailed hawks. They produced a legitimate answer to a long outstanding question in a different field...

Size and Temperature

Geographical variation in the body sizes of animals is common, and many explanations have been offered since the nineteenth century. At that time, many zoologists still believed that it should be possible to explain much of the riotous variety of life in terms of simple, formal Rules, comparable with those of physics and chemistry and based on the same properties of energy and matter that govern inanimate things. For example, warm-blooded animals living in cold climates have to expend a huge...

From Birth to the Opening of the Eyes

Infant weasels look rather alike in all species, both in their appearance at birth and in their early physical development. They are all born completely helpless, and all grow in the same way, but least and common weasels develop more rapidly than do stoats and longtails, and they reach the milestones of development at younger ages Table 9.3 . For example, although young stoats and longtails are born larger than young common weasels, they grow more slowly, and are 6 to 8 weeks old before they...

Species Diagnoses

Least Weasel Line Drawing

The general weasel appearance is common to all three species Figures 1.9. and 1.10 . The differences among them hinge mainly on size, color, and reproduction Table 1.1 . Size and color are obvious to the eye, so one might think that they would be easily defined and reliable guides. Most of the early taxonomists based their species descriptions on size and color, often using the standard practice of describing whole species or, at any rate, whole populations from one or a few type specimens. But...

Common and Least Weasels

Stickers Printing Sizes

The breeding cycles of least and common weasels are broadly similar. The gestation period is about the same 34 to 37 days both have direct implantation young females of both subspecies can breed in the summer of their birth when conditions permit Sundell 2003 and the length of the breeding season is very variable Figure 9.4A . In Europe, male common weasels can have enlarged testes and are fecund from February until at least early August, occasionally to the beginning of October. The testes...

Weasels And The Control Of Pest Mammals

Least and common weasels are the smallest and probably the most numerous carnivores in the Holarctic and, weight for weight, they eat the most. The daily food requirement of a biomass of, say, 50 kg of least common weasels would be much greater than that of an equivalent weight of foxes 50 kg of least common weasels eating 35 of their body weight in food per day see Table 2.1 would need 1,750 g of food about 88 mice , whereas 50 kg of foxes, at 8 per day, would need only 400 g 20 mice . Better...

The Mechanism of Winter Whitening

At landscape scale, there is a general relationship between cold winters and snow cover the further north the latitude or the higher the elevation is, the greater the chances are that a regular covering of snow every winter can be expected. Likewise, there is also a general connection between whitening in the landscape and in weasels. In cold climates the autumn temperatures plunge quickly, and all northern weasels always turn entirely white. The processes setting off the autumn molt, initiated...

Age and Size at Puberty

Young common weasels born early in the season, especially when food supplies are good, grow very rapidly. Early-born young of both sexes can be physically and sexually mature by the age of about 3 or 4 months. By mid- or late summer July to August , they may be taking full part in reproductive activities on equal terms with the adults, and in vole peak years their contribution is extremely important Chapter 10 . In most seasons, though, young-of-the-year females either fail to conceive or lose...