Native Red Squirrel Research Articles

Grey squirrel Sciurus carolinensis management in Italy ‐ squirrel distribution in a highly fragmented landscape

American grey squirrels Sciurus carolinensis introduced to northern Italy in 1948 have caused damage to commercial poplar plantations and have replaced the native red squirrel Sciurus vulgaris from most of the 350 km2 of the Piedmont Po‐plain they currently occupy. In order to plan a control programme aiming to stop grey squirrels from further spreading and to decrease their numbers, the current distribution and population size in the highly fragmented landscape of the Po‐plain were studied. The probability of finding grey squirrels in woodland fragments increased with habitat quality (diversity of trees producing large, consumable seeds), woodlot size and the proportion of poplar. Adding isolation variables did not improve the fit of the logistic regression model that predicted squirrel presence. The density of squirrel dreys, an index of population density, in the large Stupinigi forest also increased with tree species diversity. An estimate of the minimum population size for all woodlots assessed for squirrel presence was 1,260 animals in the summer of 1996. This extrapolates to a total of ca 2,500 grey squirrels in Piedmont. Grey squirrels continue to increase their range and are getting close to the continuous mixed forests of the pre‐Alps and to large hazel plantations. Control measures to stop the spread of grey squirrels, and eventually to eradicate them, should be implemented immediately.

Immunocontraception in rodents: a review of the development of a sperm-based immunocontraceptive vaccine for the grey squirrel (Sciurus carolinensis).

The strategy for developing contraceptive vaccines for wild rodents will depend on the species. In rats and mice, high all-year birth rates, high levels of dispersal and promiscous mating systems suggest that, if immunocontraception was used alone, > 90% of the population would have to sterilized to achieve the desired control. In Britain, the grey squirrel (Sciurus carolinensis) may be a better candidate to investigate the feasibility of a contraceptive vaccine in rodents. This introduced species is a seasonal breeder with a much lower population turnover than rats or mice. As well as causing damage to woodland, it has ousted the native red squirrel (S. valgaris) from most of the UK. A human and selective method for the control of grey squirrels is therefore highly desirable. Numerous sperm-specific antigens have been identified on rodent spermatozoa. Monoclonal antibodies to particular components block sperm-egg interactions in laboratory animals and cross-react with grey squirrel spermatozoa. In vitro fertilization assays indicate that squirrel sperm-egg binding may be inhibited also. Currently, a cDNA library obtained from grey squirrel testis is being screened to identify genes encoding specific sperm antigens involved in fertilization. Methods of enhancing immunogenicity after oral immunization using microparticle carriers and immune-stimulating complexes are currently under investigation.

An American Invasion of Great Britain: The Case of the Native and Alien Squirrel (Sciurus) Species

Abstract: The invasion of Great Britain by the gray squirrel from America has posed many interesting problems in ecology and conservation (interactions with the native red squirrel) and in forest management (the gray squirrel severely damages young stands of deciduous trees). Since 1973, mapped data on the annual distribution of the two species in state‐managed forests have been published by the Forestry Commission.Using the established methodology of annual ornithological index numbers, series of index numbers have been calculated to show the distributional dynamics of the two species. In Great Britain as a whole there has been rather limited change over the 15‐year period from 1973. However, this masks (1) the dramatic distributional decline in the red squirrel in Wales balanced by a modest expansion in Scotland, and (2) the substantial distributional increase in the gray squirrel in the small number of grid squares in Scotland in comparison with the relatively steady distribution in the large number of grid squares in England.A new index, measuring the annual replacement of one species by the other species, indicates little overall change in England and Scotland, but a net advance of the gray squirrel in Wales. A series of Markovian matrices predicted that the red squirrel would persist in forests in Scotland and in some areas of England, but would be rare in Wales. Over Great Britain as a whole, the gray squirrel is likely to occur in about twice as many forest areas as the red squirrel.

Reduced predation by pine martens on nests of Tengmalm's owl in relocated boxes

Red squirrel (Sciurus vulgaris) range within the United Kingdom (UK) has retracted significantly due to the spread of an Invasive Alien Species, the North American Eastern grey squirrel (Sciurus carolinensis). Where grey squirrels are sympatric, red squirrel populations decline through inter-specific competition and squirrelpox virus (SQPV) infection. Grey squirrel eradication from the island of Anglesey facilitated the complete restoration of native red squirrels. Although native species recovery delivered significant ecological and economic benefits, the eradication extended only to a narrow sea-channel boundary, across which grey squirrel dispersal continues to occur. Hence, the long-term sustainability of Anglesey's red squirrel population is vulnerable to grey squirrel re-establishment without continuous intervention. Recent research has demonstrated that as pine marten (Martes martes) landscape use intensity increases, so too does red squirrel occupancy, likely linked to parallel declines in grey squirrel occupancy. Restoration of this mustelid predator is a potential tool to deliver sustainable grey squirrel control by restoring a missing trophic component, depressing grey squirrel incursion rates onto Anglesey, reducing red squirrel exposure to SQPV. Recent UK pine marten translocations have sourced animals under licence from wild Scottish populations. We explore the alternative use of captive-bred founders, simultaneously introducing new genetic variability against a limited diversity within extant populations. A current conservation translocation is paired with an ongoing assessment of founder behaviour and ‘personality’ measured before release. We then highlight the multi-disciplinary approach to delivering applied red squirrel conservation programmes in the face of invasive species.

Past and present distribution of Red and Grey squirrels

AbstractThe changing fortunes of the native Red squirrel and the introduced Grey squirrel, as revealed by surveys conducted since 1930, are described The increasing distribution of the Grey squirrel is accompanied by a decline in distribution of the Red squirrel. The Grey squirrel is now found in most parts of England and Wales south of Cumbria and Northumberland, whilst the Red is located mainly in Cumbria and Northumberland, East Anglia, parts of Wales, with smaller isolated colonies on the Isle of Wight and elsewhere. In Scotland, the Grey squirrel continues to spread slowly but it is less widely distributed than the Red squirrel.

The Country Diary of a Cheshire Man

A NATURE diary, even the baldest, is ever fascinating, not only to keep but also to read. It is undoubtedly two diary-like form of Gilbert White's letters that helps them to hold their place as the great classic of country and Nature writing. The present book inevitably draws upon itself comparison with that masterpiece, a comparison from which it emerges with all credit, for it is of the authentic Selborne school, detailing the daily happenings of the countryside with a gusto that communicates itself to the reader, touching on this item and that item with an enthusiasm and insight that brings illumination to the most everyday subject. Take, for example, the following remarks on the grey squirrel and the red squirrel: “One of the alien grey squirrels, now so securely established in England, was killed in Cheshire and given me a few days ago, and it is easy to see how the belief arose that it inter-breeds with our native red squirrel, although no authentic evidence whatever of hybridization between the two species has ever come to light. The one given to me was just changing its coat, and possibly that accentuated the redness of its fur in certain parts of the body; there was a russet streak along each flank and the same colour on the face, the hind legs, and to a less extent on the back.”

The Grey Squirrel: the Introduction and Spread of the American Grey Squirrel in the British Isles, its Habits, Food and Relations with the Native Fauna of the Country

THE grey squirrel has become almost as valuable as the sea-serpent to correspondents of British newspapers, and genuine inquirers who are distraught between the assertions of the ‘prosquirrelites’ and the ‘anti-squirrelites’ will be glad to have this authoritative work at hand. It touches upon the life of the grey squirrel in its native home in eastern and central North America, but its real purpose is to describe the invader in the land it has invaded with such success that from one centre (out of about thirty) it has spread over 1,350 square miles, and that, in thirty years. The food and habits, the much discussed relations with the native red squirrel and other animals, and the economic aspects of the pest are dealt with thoroughly, the conclusion being reached that three main counts have been proved against it damage to forests by peeling bark and destroying shoots, destruction of agricultural and garden produce, including fruit, and destruction of birds eggs and young. Suggestions are made for the destruction of grey squirrels, but the seriousness of the menace in the British Isles has not yet been realised.

Grey and Red Squirrels in Britain

FOR years, naturalists have been familiar in a general way with the aptitude shown by the American grey squirrel for colonising parts of Britain, with the controversy regarding the harmfulness or otherwise of its habits, and the allegation that it has driven the native red squirrel before it. Never before, however, has an attempt at all comparable with that of Mr. A. D. Middleton * been made to collect all the facts regarding this undesirable alien before passing judgment upon it. The paper also contains information relating to the fluctuations and decline of the red squirrel in Great Britain, so important that this species, too, might well have shared a place in the title.