Is the British Red Squirrel an endangered species?

IS THE BRITISH RED SQUIRREL AN ENDANGERED SPECIES? J. G U R N E L L In Britain, the red squirrel (Sciurus vulgaris) is fully protected by law, and yet its geographic ränge continues to decline. By the year 2000 there will be few places in central and southern England and Wales where it will be found.

Fragmentation of its ränge leads to isolated populations which eventually disappear. This is the current Situation in Wales where the distribution of red squirrels is centred in the north of the country and is becoming very fragmented. In central and southern England the Situation is no better and in fact red squirrels remain in only four areas: Thetford Chase (East Anglia), Cannock Chase (Staffordshire), Hope Forest (Derbyshire) and Formby (Merseyside) (Gurnell & Pepper, in press). Red squirrels are also threatened in the north of England and southern Scotland. This is because of the apparently unstoppable spread of the grey squirrel (S. carolinensis) into these areas. Wherever red squirrels have disappeared, they have been replaced by grey squirrels.

Grey squirrels were first deliberately introduced into Britain in 1876 from eastern North America as exotic animals. By 1910 ten further introductions had occurred. Grey squirrels were also translocated within Britain many times up until the late 1930s. Since then, the grey squirrel has flourished, displacing the red squirrel as it extended its ränge. It is a very successful coloniser and does not require a continuity of trees to move between woods which may be several kilometres apart. Moreover, no natural limit to the spread of the grey squirrel has so far been detected. The British red squirrel is an endangered species, and, in the final analysis, the grey squirrel is responsible for the demise of our native species.

Even though the precise mechanisms of how the grey has replaced the red squirrel are not known, it is now believed that the answer lies in subtle differences in the way the two species use broadleaved and coniferous woodland, especially broadleaved and coniferous tree seeds (Kenward & Holm, 1989; in press). Grey squirrels appear to be well adapted to broadleaved and mixed woodlands and oust red squirrels from these types of habitat within 2 or 3 years of their arrival. They also thrive in parks and gardens and urban habitats. From work carried out in Thetford Chase in East Anglia (Gurnell, a, in press) and elsewhere, it is believed that red squirrels may have the competitive advantage over grey squirrels in extensive coniferous forests. If this is not the case, then the future of the red squirrel in Britain looks particularly bleak. An increasing problem is that blocks or ribbons of broadleaved trees are being planted within large coniferous forests as a general tactic to increase animal and plant species diversity. This provides the right conditions for the initial invasion of grey squirrels into these forests. It is believed that the long-term future of the red squirrel depends on maintaining large areas of continuous, mixed species coniferous forest with no broadleaved trees (Gurnell & Pepper, 1988; 1991).

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Offshore islands, such as the Isle of Wight, offer possible havens for the red squirrel as long as the grey squirrel is kept out (Kenward & Holm, 1989).

However, on the mainland the red squirrel will never return 011 its own accord to those parts of its f o r m e r ränge from where it has disappeared. The question for the red squirrels on the mainland is whether they are capable of surviving anywhere and, in addition, what measures should we take to try and ensure their survival. Concern for the future of the red squirrel has led to several recent or ongoing studies in different parts of the country which have been or are directed at finding out the answers to these questions (see Gurnell & Pepper, in press). It is imperative that a National Conservation P r o g r a m m e is established to coordinate these studies.

Three current research and conservation initiatives being carried out in England are of particular interest. The first initiative is called 'Red Alert'. It started in 1991 in Northumberland and includes valuable studies on the ecology of red squirrels in new coniferous forests consisting mainly of single exotic tree species such as the North American sitka spruce, Sitka pitchensis (P. Garson & P. Lutz, pers. comm.). The second initiative started in the spring of 1993 in Cumbria and North Lancashire and is considering how to conserve red squirrels in the forests within this region. Although many of these well established forests are coniferous, they contain a high proportion of mature and overmature broadleaves which pose problems in trying to keep the grey squirrel out.

The third initiative is a joint project being carried out by the Forestry Authority, Forest Enterprise, and English Nature under its Species Recovery Programme at Thetford Chase in East Anglia. Thetford Chase has been the focus of several studies on red and grey squirrels over a number of years (Gurnell, in press). Although red squirrels have survived the presence of grey squirrels for 15 to 20 years, it is now considered rare. Fifteen hundred hectares of forest have been designated a Red Squirrel Reserve. Within the Reserve, studies on practical red squirrel conservation measures are being carried out. In particular, these studies are investigating the provision of supplemental food for red squirrels in special 'red squirrel only' hoppers, the removal of grey squirrels and the management of the forest habitat in such a way as to encourage red squirrels but discourage grey squirrels. Also, it is planned to carry out a carefully programmed reintroduction of captive-bred and wild-caught red squirrels in the autumn of 1993. The results f r o m these and other timely studies are awaited with interest.

Emerging f r o m these sorts of investigation are three strategies which should form the basis of the National Conservation Programme (Gurnell & P e p p e r , in press). These strategies, which are not necessarily mutually exclusive, are: (1) The A r e a Exclusion Strategy - the protection of relatively small areas against grey squirrels where only red squirrels still exist and where the geography of the areas provides some natural barriers to the invasion of potentially colonising grey squirrels.

(2) T h e Regional Defence Strategy - the defence of a region where red squirrels still exist against the presence of grey squirrels. U n d e r this strategy, it may not be possible to eradicate grey squirrels, but numbers would be kept

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low over a long period using appropriate control and woodland management methods.

(3) The Coniferous Forest Management Strategy - the management of large coniferous habitats in a way favourable to red squirrels but unfavourable to grey squirrels (Gurnell & Pepper, 1991).

In the long-term, the Coniferous Forest Management Strategy offers the best opportunities for saving the British red squirrel. Now, there is also concern about grey squirrels in Europe. Grey squirrels were introduced into the north west of Italy 30 to 40 years ago. They are beginning to extend their ränge, damage tree and arable crops, and replace the red squirrel (Gurnell, in press, b). These grey squirrels must be eradicated, otherwise the red squirrel in Italy, and perhaps in other parts of Europe, will also become an endangered species.

References Gurnell, J. (in press a) Conserving the Red Squirrel. In Thetford Forest Park: the ecology of a pine forest. (Eds. S. Harris & P. Ratcliffe). Forestry Commission, Edinburgh.

Gurnell, J. (in press b) The grey squirrel in Britain: problems for management and lessons for Europe. Proceedings ofthe Ist'European Congress of Mammalogy.

Gurnell, J. & Pepper, H. (1988) Perspectives on the management of red and grey squirrels. In Wildlife Management in Forests. (Ed. by D C Jardine) pp. 92-109, ICF, Edinburgh.

Gurnell, J. & Pepper, H. (1991). Conserving the Red Squirrel. Research Information Note No. 205. Forestry Commission, Edinburgh.

Gurnell, J. & Pepper, H. (in press) A critical look at conserving the British red squirrel (Sciurus vulgaris). Mammal Review.

Kenward, R. E. & Holm, J. L. (1989) What future for British Red Squirrels?

Biological Journal ofthe Linnean Society, 38, 83-89.

Kenward, R. E. & Holm, J. L. (in press) On the replacement of the red squirrel in Britain: a phytotoxic explanation. Proc. R. Soc. London. B. Dr J. Gurnell, School of Biological Sciences, Queen Mary & Westfield College, London, E l 4NS

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