Wytham England

Intrigued by Lockie's results, King (1975c) began to work on the common weasels of Wytham Wood near Oxford, England, in early 1968. Wytham is a deciduous woodland, quite different from Lockie's study area, and the only common small rodents within its boundaries were wood mice and bank voles, whose combined density was always very much lower than that of the teeming field voles of the Carron Valley. In the first 6 months of trapping over the 27-ha study

Table 8.1 Some Representative Estimates of Weasel Home Ranges1

Least weasel

Stoat

Country, years

Habitat

Sex

Area (ha)

Scotland, 1960-1963

Young plantation

M

1-5

F

<1

England2, 1968-1970

Deciduous

M

7-15

woodland

F

1-4

England, 1991-1992

Farmland

M

21-192

F

4-29

Scotland3, 1971-1973

Farmland

M

9-16 (W),

10-25 (Su)

F

c.7

Scotland, 1977-1979

Farmland

M

2.4

F

1.2

Poland, 1990-1991

Deciduous forest,

M

24

rodents high

Deciduous forest,

M

167

rodents low

Iowa, 1925-1957

Farmland

M+F

4-10

Finland, 1952-1958

Mixed

M

0.6-3.0

F

0.2-2.1

Scotland, 1977-1979

Farmland

M

254

F

114

Sweden,1973-1982

Pasture and

M

8-13 (W)

marshes

F

2-7

Ontario, 1973-1975

Mixed

M

20-25

F

10-15

Switzerland,

Alpine

M

8-40

1977-1980

F

2-7

Finland, 1952-1958

Mixed

M

29-40

F

4-17

Finland, 1998-1999

Subarctic birch

M

121-207 (Su

forest, tundra

F

35-66 (Su)

Russia, 1970-1971

Meadows, scrub

M+F

11-69

forest

M+F

120-124

Alberta, 1996

Mixedwood

M

123-205

boreal forest

F

66-95

New Zealand,

Nothofagus forest,

M

93 (Su/A)

1990-1991

mice abundant

F

69 (Su/A)

New Zealand,

Nothofagus forest,

M

206 (Su/A)

1991-1992

mice scarce

F

124 (Su/A)

New Zealand, 1996

Nothofagus forest,

M

223 (Sp)

mice scarce

F

94 (Sp)

New Zealand,

Podocarp forest

M

256 (Sp)

1997-1998

M

145 (A)

F

44-123

New Zealand,

Rough grassland

M

66-215

1992, 1995

F

32-135

(Moller & Alterio 1999)

(Lockie 1966)

(King 1975c)

(Macdonald et al. 2004)

(Moors 1974)

(Pounds 1981)

(Jgdrzejwski et al. 1995)

(Jgdrzejwski et al. 1995)

(Polder 1968) (Nyholm 1959b)

(Pounds 1981)

(Erlinge 1977b)

(Simms 1979b)

(Debrot & Mermod 1983) (Nyholm 1959b)

(Hellstedt & Henttonen, in press) (Vaisfeld 1972)

(Lisgo 1999)

(Murphy & Dowding 1995) (Murphy & Dowding 1995) (Alterio 1998)

(Miller et al. 2001)

(Moller & Alterio 1999)

Table 8.1 (Continued)

Country, years

Habitat

Sex

Area (ha)

Reference

New Zealand,

Braided riverbed

M

313 (Sp)

(Dowding & Elliott

2001-2002

M

185 (Au)

2003)

F

127 (Sp)

F

116 (Au)

Longtail

Michigan, 1940

Mixed

M+F

32-160

(Quick 1944)

Colorado, 1941-1946

Mixed

M+F

80-120

(Quick 1951)

Kentucky, 1970-1975

Farmland

M

10-24

(DeVan 1982)

Indiana, 1985

Mixed

F

41

C. Vispo unpubl.

Indiana, 1998-2000

Mixed—kernel

M

180

(Gehring &

method

F

52

Swihart 2004)

Mixed—polygon

M

237

(Gehring &

method

F

39

Swihart 2004)

1. For comparison, most of these areas were calculated by the minimum convex polygon method, although some authors also presented estimates derived from the same data using other methods (see text). Data refer to year-round ranges unless specified as (Sp) spring, (Su) summer, (A) autumn, or (W) winter.

1. For comparison, most of these areas were calculated by the minimum convex polygon method, although some authors also presented estimates derived from the same data using other methods (see text). Data refer to year-round ranges unless specified as (Sp) spring, (Su) summer, (A) autumn, or (W) winter.

2. This study and the following one were both done in the same area, but in different habitats.

3. This study and the following one were done in the same area, but Moors allowed a "corridor" along fencelines of 40 m, whereas Pounds allowed 10 m.

a. Carrón Valley b. Wytham Wood a. Carrón Valley b. Wytham Wood

Figure 8.3 The patterns of winter home ranges of male common weasels. a. At high density in a young plantation in Scotland, April-October 1961 (Lockie 1966). b. At low density in deciduous woodland in England, January-February 1969 (King 1975a). Dots represent trap sites. Both sets of data plotted by the simple but debatable convex polygon method of joining the outermost traps visited by each animal. Kernel home range estimators (see text) provide more accurate estimates of home ranges but demand more data than we have found published in map form.

Figure 8.3 The patterns of winter home ranges of male common weasels. a. At high density in a young plantation in Scotland, April-October 1961 (Lockie 1966). b. At low density in deciduous woodland in England, January-February 1969 (King 1975a). Dots represent trap sites. Both sets of data plotted by the simple but debatable convex polygon method of joining the outermost traps visited by each animal. Kernel home range estimators (see text) provide more accurate estimates of home ranges but demand more data than we have found published in map form.

area, only five weasels appeared in the traps, one of them three times. But help came just in time.

While King, in some depression, took a break in August 1968, the Wytham gamekeeper borrowed some of her traps and caught four weasels in a week (and let them go, unmarked). So, he asked, what was the problem? He had applied the old gamekeeper's trick of tipping the guts of a rabbit into a plastic bag, stirring the mess around with a stick, and wiping the fragrant aroma on the entrances of the traps. King wasted no further time before applying the same method, and by the time the fieldwork part of the study ended, in June 1970, 36 common weasels had been caught a total of 348 times.

Only four males lived in the woods at any one time, each occupying at least 7 to 15 ha. Of the four, only one or two lived entirely in the woods, and the rest had parts of their ranges outside. Adjacent to the woods on one side was a young plantation, full of tall, unkempt grass and field voles. Some resident weasels living on the edge of the woods extended their ranges on that side, and their scats showed that they caught a lot of field voles in the plantation. Conversely, weasels resident in the plantation and in adjacent fields never visited the woods.

On average the resident males held their ranges for only about 7 months. When a woodland resident died, his home range was either shared between the nearest neighbors or a new weasel came in from outside. The resident weasels were well aware of their neighbors and adjusted their behavior accordingly. Excursions onto a neighbor's ground were carefully timed to coincide with the owner's absence. The four females observed always had much smaller home ranges than did males, never more than 1 to 4 ha (Figure 8.3).

Since common weasels leave their family groups when they reach independence at about 3 months of age, and most of them lived only a year or so, a different set of residents occupied the woods each year. Surprisingly, the weasels did not live any longer in the protection of Wytham (a reserve) than on game estates (King 1980c), perhaps because the density of small rodents in the wood was marginal (21 to 39 per ha).

When the density of small rodents fell still lower, in 1977-1980, the resident weasels simply disappeared. Those were the years an unlucky doctoral student, Hayward (1983), had chosen to renew research on weasels in Wytham Wood, in the same places and using the same techniques King had used. During the 12 months after August 1978, despite intense effort, Hayward caught no residents at all and only three nonresidents, once each. He came to the wry conclusion that even established weasel populations are liable to local extinction when prey resources collapse. This episode illustrates well that, contrary to popular belief, small predators do not live off the fat of the land; for most of the time, life is more chancy for them than for their prey.

The common weasels in Wytham often traveled along mole runs (Figure 8.4). King watched one, just released from a trap, darting straight down a not very obvious mole hole with every sign of confidence and familiarity. That might have

Figure 8.4 Common weasels seldom eat moles, but they frequently use mole runs and borrow the large and comfortable nests made by moles.

been a case of "any port in a storm," but, in fact, more convincing evidence showed that the Wytham weasels regularly ran along mole's runways and borrowed their nests. Among the fleas collected from them were two species specific to moles and rare on all other small mammals (see Table 11.7). The Wytham weasels very seldom ate moles, so they could have picked up those fleas only in mole nests and runways. Gamekeepers know well that common weasels use mole runs to get into rearing pens for game birds, and weasels are sometimes caught in traps set for moles.

With the development of radiotelemetry, the home ranges of the common weasels in Wytham could be worked out in much finer detail. Macdonald et al. (2004) recorded the ranges of four adult males (mean 113 ha) and two non-breeding females (28 ha), which lived in the network of linear habitats crisscrossing the farmland adjacent to the woods, but none moved more than 5 m from the cover provided by hedges and ditches. Successively tracked males occupied overlapping ranges, confirming that every vacated home was quickly taken over by others. On average, these weasels spent nearly half their time sleeping, or at least resting—all except a breeding female, which spent two thirds of the time she was tracked actively moving about, mostly in the area near the nest that probably sheltered her litter.

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