Ermine Stoats in Suffolk

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ERMINE STOATS IN SUFFOLK J. R. MARTIN The Stoat (Mustela erminea) is a widespread species in Britain, and throughout most other parts of Europe. It is very similar in appearance to the Weasel (.Mustela nivalis), and in the field confusion may arise between the two unless a clear view is obtained of the tail. The tip of the Stoat's tail is always black, but the tail of the Weasel remains brown.

However, in Britain there can be little confusion when the observer is fortunate enough to see an animal wearing a white coat, for normally only the Stoat turns white. White weasels are a great rarity in Britain (King, 1989) but in the northern parts of their European ränge weasels do turn white. However, caution should be exercised at all times in Britain, as the possibility of the animal being a white Ferret cannot be dismissed.

The reason for the coat of the Stoat turning white is often assumed to be a reaction to immediate cold weather, but this is not the case. Harrison Matthews (1952) stated that in some parts of Britain stoats nearly always turn white in winter, although in the south there was little, if any, change at all. He reported that the white coat grows beneath the old one, before the latter is moulted in the autumn, so that when it is shed the white one is revealed. He stated that the moult takes place in just a few days, during November and December, but King (1989) stated that in mild climates the moult could take place over a period of four to six weeks. The spring moult usually starts in February but could be delayed if the spring was particularly cold (King, 1989). For those records which we have dates the most common months in which ermine stoats are recorded in Suffolk are January and March (Table. 1). Harrison Matthews stated that stoats which were exposed to cold both before and during the moult turn white, and that if a stoat is exposed to cold one winter, it will turn white the following winter even if that winter is mild. This would explain why ermine stoats are sometimes seen in mild winters.

Table 1: Numbers of ermine stoats noted in Suffolk by month, including pied individuals Month No. % Month No. % October 1 2 February 10 21 November 0 March 12 28 December 4 9 April 1 2 January 16 37 July 1 2 Earliest date 29th October 1985, latest 5th April 1981 (Heathcote, 1992).

Following translocation experiments in North America, King (1989) reported that heredity played an important role in coats turning white, as well as temperature. She stated that in an area where it is always sunny or very mild ft is easy to predict whether a white coat will be needed or not. She considered that only in a 'zone of indecision' is it an advantage to have a temperature 'switch' thus enabling an animal to make an adjustment one way or another.

The switch may turn off the supply of melanin whilst the new fĂźr grows on the tail and sides; but by the time the new dorsal fĂźr is growing, it may be turned

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Suffolk Natural History, Vol. 32

on again. The result is that the animal appears to be 'pied'. Where the weather conditions are very variable there may be a mixture of white, brown, and pied individuals. The animals look as if they were caught in the middle of moulting, but they are more often wearing a full-grown winter coat which, as it were, changed its mind about turning white. Five of the detailed sightings in Suffolk related to pied individuals, and all related to stoats which had been seen in the past 10 years. It is likely though that others have gone un-recorded in the past.

Therefore, the ability to adopt a white coat is not due to the current weather conditions, but as a response to weather conditions experienced prior to the moult. However, once the ability to do that has been obtained, then the ability to switch to a white coat in subsequent winters is retained.

King further reported that the critical temperature below which new für grows only white is different for different parts of the body. It has been calculated in Russia (Gaiduk, in King, 1989) that the für of the hindquarters and lower flanks of stoats grows white if the temperature is 2°C, but it has to fall below -1°C before the head and back turns white. It should be noted that the animal which was seen on 2Ist December 1994 at Pakefield was all white except for some brown on the legs. A remarkable sighting was made by R. Andrews at Castle Marsh, near Barnby, on 16th July 1982, when he saw a stoat which 'still had pure white colour on the front of its body and normal brown summer pelage on its back half together with a black tip to the tail*. At the time it was commented that this was a most unusual colouration and was considered of a rare occurrence. All other 'pied' stoats in Suffolk were wearing winter coats in line with the norm, i.e. brown on the upper parts of the body.

This would suggest that both of those animals were under-going a spring moult!

In cold climates the autumn temperatures plunge quickly to below -1°C, so all of the stoats turn entirely white. However, in milder regions the critical temperatures required for whitening may be different, probably higher, and the autumn weather may be more variable, so that the threshold may be exceeded for one part of the body, but not for another.

It appears that in Britain the transitional zone for stoats turning white is between 52 and 56 degrees north. King (1989) stated that white coats for stoats were common in Scotland and Wales, with brown the normal colouration for those stoats living in southern and eastern counties. Her Statement was made on the basis of observations by viewers of the BBC wildlife programme 'Wildtrack' during the winter of 1 9 8 3 ^ . There were no reported sightings of ermine stoats in Suffolk in that winter (Table 2).

Apart from the reports shown (Table 2), a group of naturalists carried out a non-related study in the King's Forest of north-west Suffolk during the period 1981-1992 (see Heathcote, 1992). During that time they recorded a number of stoats, of which eleven were recorded in füll ermine, and a further six in partial ermine. Füll ermine or pied stoats were seen in most years of the study.

Despite a search of records held at the Colchester Museum, I am not aware of any reported ermine, or partial ermine, stoats for north Essex, and no sightings in the whole of Essex were reported by Hughes (1986). However, in Norfolk ermine stoats are regularly recorded. In the 20 years since 1975 they have been recorded in 13, and the only years they have not been reported in the

Trans. Suffolk Nat. Soc. 32 (1996)

ERMINE STOATS IN SUFFOLK

last 10 years were 1985 and 1993. Pied stoats have been seen at the same site just over the County boundary in Cambridge, during the winters of early 1993 and early 1994 (P. Strachan pers. comm.).

Stoats in ermine

Conclusions Ermine stoats have been reported from throughout Suffolk. There appears to be no pattern to the distribution, other than that which has been reported at present on the general distribution of the Stoat in Suffolk (Martin & Sanford, 1996). It should be noted though, that with the exception of the specimen recorded from Shotley (TM23), all of the pied animals were recorded from the northern parts of Suffolk, ie TL77, TL87, TM48 and TM58. This is contrary to what would perhaps be expected, with most, if not all, of the pied animals being recorded from the south of the County.

With so little data it is difficult to draw any positive conclusions, and so I urge all recorders to continue sending in detailed records of ermine stoats, for it is quite clear that ermine stoats, although not common in Suffolk, are not as rare as once thought.

Acknowledgements I thank the following for responding to my request for ermine stoat records: Mrs M. Beard, M. Bone, Owen Johnson, Peter Lawson, Hugh McK. Butcher, Philip Murphy, Eric Parsons, Rufus Sweetman, Patrick Ramsey,

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A. Riseborough, Philip Strachan, Les Tarver, John Wakerley and Peter Wilson.

I also thank Mrs Mary Hovells and P. Jackson.

I am grateful to Martin Sanford for producing the distribution map, as well as reading the text and passing helpful and constructive comment.

References Heathcote, G., (1992). Stoats in the King's Forest. Trans. Suffolk Nat. Soc., 29:57.

Hughes, F., (1986). A Provisional Atlas of the Mammals of Essex. Passmore Edwards Museum, London.

King, C. (1989). The Natural History ofWeasels and Stoats. Helm, London.

Martin, J. & Sanford, M. (1996). The Third Provisional Atlas of Suffolk Mammals. Suffolk Biological Records Centre, Ipswich.

Matthews, L. H„ (1952). British Mammals. Collins, London.

Records of ermine stoats were extracted from the following volumes of the Society's Transactions:- 18:319,19:394, 23:70, 24:99.

The Norfolk Mammal Reports from 1975 to 1994 were also consulted.

J. Martin, 17 Moss Way, West Bergholt, Colchester, Essex C 0 6 3LJ Table 2: Ermine Stoats in Suffolk DATE 1903 13 MAR 1930 16 MAR 1930 DEC 1937 JAN 1938 DEC 1938 DEC 1965 16 JAN 1971 08 FEB 1977 08 MAR 1978 JAN 1980 JAN 1980 Winter 1980 Winter 1980 Winter 1980 24 JAN 1981 22 MAR 1982 16JUL 1982 29 OCT 1985 01 MAR 1986 16 MAR 1987 17 MAR 1987 12 JAN 1988

LOCATION Eriswell Ferry, Butley Monk Soham Stowmarket Butley Butley Cliff Lane, Ipswich Meadow, Ash Plantation Bradfield Woods Benacre Lakenheath Warren Orford Campsey Ash Benacre Henham Estate Barton Mills King's Forest Bamby King's Forest West Stow King's Forest King's Forest Wrentham

GRID TL7178 TM3948 TM2065 TM0458 TM3651 TM3651

SOURCE

Morley, C.

COMMENT 7 partial and füll ermine füll ermine ermine ermine ermine ermine

TM1643

Mr Bone

füll ermine

TL763728 TL9357 TM535845 TL7680 TM4249 TM3355 TM5184 TM4577 TL724719 TL8076 TM472913 TL8174 TL8071 TL8273 TL8276 TM4982

Jackson, P. Wakerley, J. C. Beard, Mrs M.

ermine füll ermine ermine ermine ermine ermine ermine ermine ermine In ermine partial ermine In ermine partial ermine In ermine In ermine partial ermine

Trans. Suffolk Nat. Soc. 32 (1996)

Raincock, J. Raincock, J. Raincock, J. Raincock, J.

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ERMINE STOATS IN SUFFOLK

DATE 23 M A R 1988 0 2 F E B 1990 03 F E B 1990 16 F E B 1990 05 J A N 1991

LOCATION Spexhall Churchyard King's Forest Easton King's Forest West Stow Country Park West Stow Country Park

GRID SOURCE T M 3 7 8 8 0 1 Hovells, M. TL8273 TM2959 TL8272

Raincock, J. Parsons, E. Raincock, J.

TL805708

Beard, M.

TL7971

M c K . Butcher, H.

COMMENT In ermine In ermine ermine In ermine

17 F E B 1991

Boyton Marshes

TM3847

Piotrowski, S. H.

09 J A N 1993 J A N 1994 0 2 J A N 1994 16 J A N 1994 20 F E B 1994 18 M A R 1994

Cavenham Lineage Wood Mettingham Ramsholt King's Forest Cranes Creek, Shotley Pakefield Pakefield Ixworth Ramsholt Carlton Colville

TL761708 TL8848 TM364909 TM310410 TL87D

Sweetman, R. Johnson, O. Riseborough, A. Ramsey, P. Lack, Dr P. C.

In ermine Bank of R. Lark, ermine, chasing a wren In ermine, being carried

by Heron partial ermine ermine ermine ermine In ermine

TM244360 TM5389 TM5389 TL9172 TM295444 TM497915

Murphy, P. W. Blomfield Mrs S. Lawson, P. G. Wilson, P. G. H. Ramsey, P. Tarver, L .

partial ermine Partial ermine partial ermine ermine ermine ermine

29 J A N 1991

21 21 18 19 27

D E C 1994 D E C 1994 M A R 1995 M A R 1995 J A N 1996

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(1996)