Foods Of Common Weasels In Britain And Western Europe

Common weasels have been studied more widely than least weasels, in part because in Western Europe it is the common weasel that lives in the humanized landscapes surrounding cities. University students and professors prefer nearby sites

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Figure 5.2 Some representative examples of the food habits of local populations of long-tailed weasels. (a) Manitoba (n = 200, Gamble & Riewe 1982); (b) Ontario (n = 34, Simms 1979b); (c) Pennsylvania (n = 112, Glover 1942b); (d) New York (Hamilton 1933); (e) Colorado (n = 84, Quick 1951); (f) Iowa, (n = 166, Polderboer et al. 1941). Prey designated as in Figure 5.1A.

for field studies, when possible, and have tended to avoid the distant northern climes, with long winters and difficult working conditions, that support least weasels.

The first general study of the foods of common weasels (and stoats) in Britain was that of Day (1968) (Figure 5.3i). Day's work has been widely quoted, and for many years was the only British study to include animals of both species of weasels collected (mostly from gamekeepers) from all over the country. His identification key to the hairs of the small mammals of Britain (Day 1966) opened the door to many later studies. Recently, McDonald et al. (2000) (Figure 5.3j) made a second comparative study of the two species, also from carcasses collected from gamekeepers across Britain. In both studies, small rodents dominated the diet of common weasels (1960s, 56%; 1990s, 68%). Both stoats and common weasels ate rabbits more often in the 1990s than they had done 30 years before (stoats 65% vs. 25%; common weasels 25% vs. 18%), but for different reasons. By the 1990s, rabbits had recovered from myxomatosis, so stoats could return to their specialized niche as rabbit hunters, and common weasels benefited from the greater availability of young rabbits in spring.

Young plantations are an ideal habitat for weasels, because the ground between the trees quickly becomes overgrown with grass, neither mown nor grazed, providing ideal living conditions for the favorite prey of all weasels, voles of the genus Microtus. In such places, common weasels eat almost only voles (Lockie 1966). Two of the four habitats observed in southern Sweden by Erlinge (1975) were young

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Figure 5.3 Some representative examples of the food habits of local populations of least and common weasels. (a) North America (Hall 1951); (b) Northern European USSR, tundra and taiga (Parovschikov 1963); (c) Sweden (Erlinge 1975); (d) the Netherlands (n = 161, Brugge 1977); (e) Poland (n = 15, Jgdrzejewska & Jgdrzejewski 1998); (f) Scotland (n = 206, Moors 1974); (g) England (n = 445, Tapper 1979); (h) England (n = 285, King 1980d); (i) Britain 1960s, rabbits few (n = 152, Day 1968); (j) Britain 1990s, rabbits recovered (n = 458, Springs n = 131, Summers n = 66, Autumns n = 60, Winters n = 27; McDonald et al. 2000). Prey designated as in Figure 5.1A.

Figure 5.3 Some representative examples of the food habits of local populations of least and common weasels. (a) North America (Hall 1951); (b) Northern European USSR, tundra and taiga (Parovschikov 1963); (c) Sweden (Erlinge 1975); (d) the Netherlands (n = 161, Brugge 1977); (e) Poland (n = 15, Jgdrzejewska & Jgdrzejewski 1998); (f) Scotland (n = 206, Moors 1974); (g) England (n = 445, Tapper 1979); (h) England (n = 285, King 1980d); (i) Britain 1960s, rabbits few (n = 152, Day 1968); (j) Britain 1990s, rabbits recovered (n = 458, Springs n = 131, Summers n = 66, Autumns n = 60, Winters n = 27; McDonald et al. 2000). Prey designated as in Figure 5.1A.

plantations and in both, voles were the single most important prey (Figure 5.3c). In spring when voles were scarce, male weasels turned to the newly available young rabbits. Scats also contained bank voles, wood mice, water voles, and shrews and, in one of the plantations, also birds and even lizards. Weasels avoided an older spruce plantation and a deciduous alder woodland. The trees at these sites were tall enough to shade out the grass, and few rodents ventured out on to the bare ground.

In Wytham Woods, near Oxford, King (1980b) collected 250 scats from 36 individually marked common weasels caught in wooden box traps. To make sure she got a sample from each captured weasel, she supplied a dead white mouse in each trap. The populations of small rodents in the area were rather low (21 to 39/ha), and the weasels were usually hungry enough to eat the lab mouse even if it became distinctly "ripe." Eating something shoved everything else previously eaten along in the gut, and the usual result was at least one sample of each weasel's last wild-caught meal. White fur in scats showed clearly where wild meals stopped. The Wytham weasels ate mostly bank voles, wood mice, field voles, and birds, more or less in the order of their abundance. Bank voles were by far the most common of the small rodents in the wood, followed by wood mice. Few field voles lived in the wood, but some were killed by the weasels whose home ranges extended to a neighboring young plantation (Figure 5.3h). Wytham had very few rabbits and no rats at the time. There were plenty of shrews and moles, but no shrews and only one mole appeared in the scats.

Interesting and important as it is to know what weasels eat in woodlands of different types, these habitats are in the minority. In Britain, woodland comprises less than a tenth of the total land area, whereas arable and pasture land comprise two thirds of England and Wales, and almost a quarter of Scotland. The majority of British weasels live on farmland. In open country, the small rodents most often eaten by common weasels are field voles, which are at home in any kind of grassland, and wood mice, which often live in hedges and are not afraid to venture out into the farmers' fields, especially before harvest. Bank voles stick to thick cover, so they are less often caught in open country than in woodland.

In general, then, common weasels depend on small rodents and small birds, and where these are scarce, such tiny hunters do not thrive. In every sample shown in Figure 5.3, as well as in other samples not shown, the proportion of small rodents in the common weasels' diet is never less than half of the total number of prey items identified, and is often nearer to three quarters.

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