Chest-spot on Long-tailed Field Mouse

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NOTES

ON T H E CHEST-SPOT ON LONG-TAILED FIELDMOUSE (Apodemus s. sylvaticus Linn.)

THE

THE garden at Great Glemham House consists of a walled garden and some 5 acres of what before the war was shrubbery and lawns, now mainly better described as rough grass and woodland. It is situated in the middle of a small park which is itself surrounded by woodland, mostly coppice and oak Standards ; Apodemus sylvaticus is of course abundant throughout the whole wooded area. Apodemus does not seem to travel far from its nest and the minimum distance of some 150 yards which separates the garden and an adjacent copse from the woodland surrounding the park is probably far enough to ensure that the population found in t h e garden is a self-contained Community so far as breeding is concerned. T h e ehest spot of A. sylvaticus varies considerably in size : it is sometimes absent but usually consists of a larger o r smaller buffish longitudinal patch between the forelegs, occasionally spreading sideways, sometimes far enough to form a complete collar. There is in the garden a small population of the Yellow-necked woodmouse (A. flavicollis wintoni Barret-Hamilton). Apart f r o m those mentioned below, I have examined 6 or 8 individuals over the last 5 years, mainly brought into the house by cats, a n d in all the ehest spot was large, forming a complete collar, often extending backwards towards the belly as a wider or narrower median stripe. A. flavicollis is a decidedly larger animal than A. sylvaticus with a hindfoot of 23-27 mm. as opposed to 21-23mm. It has been suggested that A. sylvaticus and flavicollis are not speeifieally distinet and may interbreed in the wild, though so far as I am aware they have never been induced to do so in captivity. If interbreeding did occur in the relatively isolated populations in the garden at Great Glemham House it would seem that it might show itself amongst the A. sylvaticus in agreater average size of the ehest spot and of individual speeimens absolutely. Düring the latter half of December, 1953, and again in March, 1954, traps were set in the garden and in a wood 500 yards away in which no A. flavicollis have been found. T h e results are set out below :— Garden. Wood. Spot absent or minute, at most a few buff coloured hairs Spot small, less than 10 mm. long Spot medium, 10-20 mm. long Spot forming a collar A. flavicollis

7 34 3 —

6

8 18 20 1 —


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Chest-spot on Long-tailed Field Mouse by Suffolk Naturalists' Society - Issuu