The Experts below are selected from a list of 294 Experts worldwide ranked by ideXlab platform
Kore Schlottau - One of the best experts on this subject based on the ideXlab platform.
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Analysis of exotic squirrel trade and detection of human infections with variegated squirrel bornavirus 1, Germany, 2005 to 2018
Euro surveillance : bulletin Europeen sur les maladies transmissibles = European communicable disease bulletin, 2019Co-Authors: Dennis Tappe, Christina Frank, Timo Homeier-bachmann, Hendrik Wilking, Valerie Allendorf, Kore Schlottau, César Muñoz-fontela, Monika Rottstegge, Julia R Port, Jürgen RisslandAbstract:Following the discovery in 2015 of the variegated squirrel bornavirus 1 (VSBV-1) in fatal encephalitis cases among exotic squirrel breeders and a zoo animal caretaker in Germany, a case definition was developed. It was employed during trace-back animal trade investigations and sero-epidemiological studies among breeders and zoo animal caretakers of holdings with VSBV-1 infected Squirrels. During the investigation, two possible human cases who had died of encephalitis were identified retrospectively among the squirrel breeders. Moreover, one probable human case was detected among the breeders who had a positive memory T-cell response to VSBV-1 antigen and antibodies against VSBV-1. The low rate of seropositivity found among living persons in risk groups that handle exotic Squirrels privately or at zoos may reflect rareness of exposure to VSBV-1 during animal contact, a high lethality of infection or a combination of these factors. As a precaution against human exposure, testing of exotic Squirrels for VSBV-1 infection and/or avoiding direct contact with exotic Squirrels in zoos and private holdings is strongly advised.
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Multiple detection of zoonotic variegated squirrel bornavirus 1 RNA in different squirrel species suggests a possible unknown origin for the virus
Archives of Virology, 2017Co-Authors: Kore Schlottau, Martin Beer, Rainer G. Ulrich, Timo Homeier-bachmann, Christine Fast, Bernd Hoffmann, Donata HoffmannAbstract:The recently discovered variegated squirrel bornavirus 1 (VSBV-1) caused the death of three squirrel breeders in Germany. Subsequent first screening of Squirrels with in vivo collected swab samples and a VSBV-1-specific RT-qPCR revealed not only variegated squirrel infections ( Sciurus variegatoides ), but also Prevost’s Squirrels ( Callosciurus prevostii ) as positive for VSBV-1 genome. In this study, 328 Squirrels were tested using the established RT-qPCR assays. In 16 individual animals VSBV-1 RNA could be detected; 15 individuals were from small breedings and zoological gardens in Germany, with the remaining individual being from a zoological garden in Croatia. Positive animals belonged to the species C. prevostii, C. finlaysonii , and Tamiops swinhoei within the subfamily Callosciurinae and Sciurus granatensis within the subfamily Sciurinae. Repeated non-invasive oral swab sampling in one holding indicated positive animals months after a first negative result. Besides the oral swabs, VSBV-1 was also detected in fecal (pool) samples allowing the future monitoring of squirrel holdings based on RT-qPCR investigation of such samples. The detection in zoological gardens emphasizes the need for further investigations into the transmission route to humans in order to develop rational public health measures for prevention of transmission. Finally, the detection of several closely related VSBV-1 sequences in Squirrels from different subfamilies raises questions as to the origin of the virus.
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variegated squirrel bornavirus 1 in Squirrels germany and the netherlands
Emerging Infectious Diseases, 2017Co-Authors: Kore Schlottau, Dirk Höper, Maria Jenckel, Judith M A Van Den Brand, Christine Fast, Christiane Herden, Jens Thielebein, Niels Mensing, Timo Homeierbachmann, Bert DienderAbstract:We screened Squirrels in Germany and the Netherlands for the novel zoonotic variegated squirrel bornavirus 1 (VSBV-1). The detection of VSBV-1 in 11 Squirrels indicates a considerable risk for transmission to humans handling those animals. Therefore, Squirrels in contact with humans should routinely be tested for VSBV-1.
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Variegated Squirrel Bornavirus 1 in Squirrels, Germany and the Netherlands.
Emerging infectious diseases, 2017Co-Authors: Kore Schlottau, Dirk Höper, Timo Homeier-bachmann, Maria Jenckel, Judith M A Van Den Brand, Christine Fast, Christiane Herden, Jens Thielebein, Niels Mensing, Bert DienderAbstract:textabstractWe screened Squirrels in Germany and the Netherlands for the novel zoonotic variegated squirrel bornavirus 1 (VSBV-1). The detection of VSBV-1 in 11 Squirrels indicates a considerable risk for transmission to humans handling those animals. Therefore, Squirrels in contact with humans should routinely be tested for VSBV-1.
Bert Diender - One of the best experts on this subject based on the ideXlab platform.
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variegated squirrel bornavirus 1 in Squirrels germany and the netherlands
Emerging Infectious Diseases, 2017Co-Authors: Kore Schlottau, Dirk Höper, Maria Jenckel, Judith M A Van Den Brand, Christine Fast, Christiane Herden, Jens Thielebein, Niels Mensing, Timo Homeierbachmann, Bert DienderAbstract:We screened Squirrels in Germany and the Netherlands for the novel zoonotic variegated squirrel bornavirus 1 (VSBV-1). The detection of VSBV-1 in 11 Squirrels indicates a considerable risk for transmission to humans handling those animals. Therefore, Squirrels in contact with humans should routinely be tested for VSBV-1.
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Variegated Squirrel Bornavirus 1 in Squirrels, Germany and the Netherlands.
Emerging infectious diseases, 2017Co-Authors: Kore Schlottau, Dirk Höper, Timo Homeier-bachmann, Maria Jenckel, Judith M A Van Den Brand, Christine Fast, Christiane Herden, Jens Thielebein, Niels Mensing, Bert DienderAbstract:textabstractWe screened Squirrels in Germany and the Netherlands for the novel zoonotic variegated squirrel bornavirus 1 (VSBV-1). The detection of VSBV-1 in 11 Squirrels indicates a considerable risk for transmission to humans handling those animals. Therefore, Squirrels in contact with humans should routinely be tested for VSBV-1.
John Gurnell - One of the best experts on this subject based on the ideXlab platform.
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poxviral disease in red Squirrels sciurus vulgaris in the uk spatial and temporal trends of an emerging threat
Ecohealth, 2008Co-Authors: A W Sainsbury, John Gurnell, Colin Mcinnes, Robert Deaville, Becki Lawson, W A Cooley, Stephan S J Farelly, Michael J Stack, Paul Duff, P H RussellAbstract:The squirrel poxvirus (SQPV) is the probable mediator of apparent competition between the introduced invading gray squirrel (Sciurus carolinensis) and the red squirrel (Sciurus vulgaris) in the UK, and modeling studies have shown that this viral disease has had a significant impact on the decline of the red squirrel in the UK. However, given our limited understanding of the epidemiology of the disease, and more generally the effects of invasive species on parasite ecology, there is a need to investigate the transmission dynamics and the relative pathogenicity of the virus between species. We aimed to increase our knowledge of these processes through an empirical study in which we: (i) used pathological signs and transmission electron microscopy (TEM) to diagnose SQPV disease in red Squirrels found dead during scanning surveillance between 1993 and 2005; (ii) detected antibody to SQPV using an enzyme-linked immunosorbent assay (ELISA) in the same animals; and (iii) mapped cases of the disease, and the gray squirrel distribution, using a geographical information system. We analyzed the distribution of cases of SQPV disease according to woodland type, a measure of squirrel density. SQPV disease occurred only in areas of England also inhabited by seropositive gray Squirrels, and as the geographical range of gray Squirrels expanded, SQPV disease occurred in these new gray squirrel habitats, supporting a role for the gray squirrel as a reservoir host of the virus. There was a delay between the establishment of invading gray Squirrels and cases of the disease in red Squirrels which implies gray Squirrels must reach a threshold number or density before the virus is transmitted to red Squirrels. The spatial and temporal trend in SQPV disease outbreaks suggested that SQPV disease will have a significant effect on Scottish populations of red Squirrels within 25 years. The even spread of cases of disease across months suggested a direct rather than vector-borne transmission route is more likely. Eight juvenile and sub-adult free-living red Squirrels apparently survived exposure to SQPV by mounting an immune response, the first evidence of immunity to SQPV in free-living red Squirrels, which possibly suggests a changing host-parasite relationship and that the use of a vaccine may be an effective management tool to protect remnant red squirrel populations.
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Squirrel poxvirus: Landscape scale strategies for managing disease threat
Biological Conservation, 2006Co-Authors: John Gurnell, Peter W. W. Lurz, Stephen P. Rushton, Anthony W. Sainsbury, P. F. Nettleton, Mark D. F. Shirley, C. Bruemmer, N. GeddesAbstract:Abstract Squirrel poxvirus (SQPV) is a well-documented example of pathogen-mediated competition between an invasive species, the grey squirrel ( Sciurus carolinensis ), and a native species, the Eurasian red squirrel ( Sciurus vulgaris ). SQPV causes disease with high mortality in red Squirrels but appears non-pathogenic in grey Squirrels. Not all populations of introduced grey Squirrels carry the virus, notably those in Scotland and Italy, and the rate of red squirrel replacement by grey Squirrels is some twenty times faster in those areas where grey Squirrels carry the virus. Here we develop strategies to manage the SQPV disease threat to red Squirrels by reference to the largest, designated red squirrel refuge site in England, Kielder Forest (50 000 ha). Using modelling techniques, we identify four main corridors within the buffer zone by which grey Squirrels will reach Kielder, initially within two years and in large numbers within 10 years. Assuming that greys will not settle within Kielder because of the unfavourable nature of the spruce habitat, we predict that SQPV disease will burn out at the edges of the forest, although many red Squirrels will die. This burn-out is unlikely to be the scenario in other refuge areas where the habitat is more favourable to greys. We conclude that the conservation of red Squirrels will depend on minimising contact between red and grey squirrel populations, and we advocate monitoring grey Squirrels in corridors within buffer zones around refuge areas, and removing them when detected.
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Alien species and interspecific competition: effects of introduced eastern grey Squirrels on red squirrel population dynamics
Journal of Animal Ecology, 2004Co-Authors: John Gurnell, Luc A Wauters, Peter W. W. Lurz, Guido TosiAbstract:Summary 1. Throughout much of Britain, Ireland and north Italy, red Squirrels ( Sciurus vulgaris L.) have been replaced by alien grey Squirrels ( S. carolinensis Gmelin) introduced from North America. We have studied Squirrels in two mixed woodlands in north Italy and two conifer forests in north England. In each country, one site was occupied by red Squirrels and one site by both species. 2. We have previously considered interference competition and exploitation competition for food and space between red and grey Squirrels and have showed that grey Squirrels caused reduced body growth in juvenile and subadult red Squirrels, and compete for tree seeds cached by adult red Squirrels in spring. Here we report on the effects of grey Squirrels on three fitness components in red Squirrels that have consequence at the population level: fecundity, residency and recruitment. 3. Litter production peaked in the spring and summer, but fewer females bred in the summer with grey Squirrels present. In addition, fewer individual red squirrel females produced two litters per year in the sites with grey Squirrels. Moreover, red squirrel recruitment rate and, in the mixed broadleaf sites, red squirrel juvenile residency, decreased with increasing grey squirrel density. 4. Fecundity of individual female red Squirrels was lower in red‐grey than in red-only sites because they had a lower body mass in sites with grey Squirrels. 5. Overall, there was no significant effect of grey Squirrels on residency of adult red Squirrels or on population turnover rate. However, the presence of grey Squirrels resulted in a reduction in red squirrel fitness which was evident by lower population summer breeding and a lower recruitment. Over time, this will result in a decline in population size and eventually population extinction.
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Modeling impacts and costs of gray squirrel control regimes on the viability of red squirrel populations
The Journal of Wildlife Management, 2002Co-Authors: Stephen P. Rushton, Peter W. W. Lurz, John Gurnell, Robin M. FullerAbstract:The introduced gray squirrel (Sciurus carolinensis) is a principal threat to the populations of the red squirrel (S. vulgaris). We used a spatially explicit population dynamics model to investigate the changes of red and gray squirrel populations in landscapes to assess the effects of gray squirrel population control methods on red squirrel population viability. We analyzed 2 methods of gray squirrel population control: (1) trapping where adults were killed on an annual basis, and (2) immunocontraception where reproduction was suppressed. The model was run under a range of efficiency and intensity of control as well as red and gray squirrel life-history scenarios created by Latin Hypercube Sampling of the realistic parameter range for both demographic and control variables. The viability of squirrel populations in 2 contrasting landscape scenarios was investigated: (1) Thetford Forest, East Anglia, United Kingdom (UK), where a small isolated population of red Squirrels is surrounded by a large population of gray Squirrels; and (2) Redesdale Forest, Northumberland, UK, where red Squirrels are still in abundance and the first gray Squirrels were observed to disperse into the area from Scotland. In the absence of population control of gray Squirrels, red squirrel populations were predicted to become extinct in both landscapes within 15 years at Thetford and 6 years at Redesdale. Immunocontraception did not lead to persistent populations at Thetford but allowed red Squirrels to persist in Redesdale. Removal of gray Squirrels by trapping at both sites was predicted to lead to red squirrel population persistence. Our findings suggest that immunocontraception is unlikely to be effective unless it is applied to a large portion of the target and surrounding population. Our results also indicate that an integrated control strategy, incorporating both trapping and immunocontraception, may be the best option for controlling gray Squirrels. This integrated strategy needs to include the relative costs of control, and it may be that immunocontraception provides the best overall solution in areas where gray Squirrels are low in abundance.
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Grey Squirrels have high seroprevalence to a parapoxvirus associated with deaths in red Squirrels
Animal Conservation, 2000Co-Authors: Anthony W. Sainsbury, P. F. Nettleton, Janice Gilray, John GurnellAbstract:The population of red Squirrels (Sciurus vulgaris) in the British Isles is in decline and is being supplanted by the grey squirrel (Sciurus carolinensis). It has been suggested that parapoxvirus-associated disease has caused significant mortality in red Squirrels and that grey Squirrels are the source of the virus. A direct enzyme-linked immunosorbent assay (ELISA) was developed for the measurement of antibody to squirrel parapoxvirus. We tested 140 sera from red Squirrels and 223 from grey Squirrels from different populations in the UK. A high percentage (61%) of apparently healthy grey Squirrels, were found to have been exposed to the parapoxvirus. Only 2.86% (4/140) of red Squirrels had antibody and three of these animals had parapoxvirus-associated disease. We postulate that the grey squirrel may act as a reservoir host for the virus.
Christine Fast - One of the best experts on this subject based on the ideXlab platform.
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Multiple detection of zoonotic variegated squirrel bornavirus 1 RNA in different squirrel species suggests a possible unknown origin for the virus
Archives of Virology, 2017Co-Authors: Kore Schlottau, Martin Beer, Rainer G. Ulrich, Timo Homeier-bachmann, Christine Fast, Bernd Hoffmann, Donata HoffmannAbstract:The recently discovered variegated squirrel bornavirus 1 (VSBV-1) caused the death of three squirrel breeders in Germany. Subsequent first screening of Squirrels with in vivo collected swab samples and a VSBV-1-specific RT-qPCR revealed not only variegated squirrel infections ( Sciurus variegatoides ), but also Prevost’s Squirrels ( Callosciurus prevostii ) as positive for VSBV-1 genome. In this study, 328 Squirrels were tested using the established RT-qPCR assays. In 16 individual animals VSBV-1 RNA could be detected; 15 individuals were from small breedings and zoological gardens in Germany, with the remaining individual being from a zoological garden in Croatia. Positive animals belonged to the species C. prevostii, C. finlaysonii , and Tamiops swinhoei within the subfamily Callosciurinae and Sciurus granatensis within the subfamily Sciurinae. Repeated non-invasive oral swab sampling in one holding indicated positive animals months after a first negative result. Besides the oral swabs, VSBV-1 was also detected in fecal (pool) samples allowing the future monitoring of squirrel holdings based on RT-qPCR investigation of such samples. The detection in zoological gardens emphasizes the need for further investigations into the transmission route to humans in order to develop rational public health measures for prevention of transmission. Finally, the detection of several closely related VSBV-1 sequences in Squirrels from different subfamilies raises questions as to the origin of the virus.
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variegated squirrel bornavirus 1 in Squirrels germany and the netherlands
Emerging Infectious Diseases, 2017Co-Authors: Kore Schlottau, Dirk Höper, Maria Jenckel, Judith M A Van Den Brand, Christine Fast, Christiane Herden, Jens Thielebein, Niels Mensing, Timo Homeierbachmann, Bert DienderAbstract:We screened Squirrels in Germany and the Netherlands for the novel zoonotic variegated squirrel bornavirus 1 (VSBV-1). The detection of VSBV-1 in 11 Squirrels indicates a considerable risk for transmission to humans handling those animals. Therefore, Squirrels in contact with humans should routinely be tested for VSBV-1.
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Variegated Squirrel Bornavirus 1 in Squirrels, Germany and the Netherlands.
Emerging infectious diseases, 2017Co-Authors: Kore Schlottau, Dirk Höper, Timo Homeier-bachmann, Maria Jenckel, Judith M A Van Den Brand, Christine Fast, Christiane Herden, Jens Thielebein, Niels Mensing, Bert DienderAbstract:textabstractWe screened Squirrels in Germany and the Netherlands for the novel zoonotic variegated squirrel bornavirus 1 (VSBV-1). The detection of VSBV-1 in 11 Squirrels indicates a considerable risk for transmission to humans handling those animals. Therefore, Squirrels in contact with humans should routinely be tested for VSBV-1.
Peter W. W. Lurz - One of the best experts on this subject based on the ideXlab platform.
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Widespread occurrence of squirrel adenovirus 1 in red and grey Squirrels in Scotland detected by a novel real-time PCR assay.
Virus research, 2018Co-Authors: Kerstin Wernike, Peter W. W. Lurz, Claudia Wylezich, Dirk Höper, Julia Schneider, Anna Meredith, Elspeth Milne, Martin Beer, Rainer G. UlrichAbstract:Abstract The Eurasian Red Squirrel (Sciurus vulgaris) is distributed throughout large parts of Europe and Asia. However, its distribution in certain regions of Europe is endangered by the invasive, non-native Grey Squirrel (Sciurus carolinensis). Adenoviruses were already described in Squirrels in Great Britain almost two decades ago. In 2013, a squirrel adenovirus (SqAdV-1) was additionally found in a red squirrel from Germany, which suffered from acute diffuse catarrhal enteritis, and the complete genome sequence was determined. Here, samples from dead red (n = 25) and grey (n = 12) Squirrels collected in Scotland, UK, were analysed for the presence of this squirrel-associated virus. By using a newly developed real-time PCR targeting the adenoviral polymerase gene, viral DNA was detected in at least one of four tissue samples tested per animal in 64.0% of the red Squirrels and 41.7% of the grey Squirrels. Exceptionally high viral genome loads were detected in the intestine and liver, but SqAdV-1 DNA was also present in lung and kidney samples of affected animals. Almost complete genome sequence determination of a red squirrel-derived SqAdV-1 strain from Scotland indicated a very high degree of identity to the first German strain. Sequence analysis of the hexon gene, which encodes one of the major antigens of the virion, revealed an identity of 100% between viruses found in red and grey Squirrels from Scotland. In conclusion, SqAdV-1 appears to be widespread in the Scottish red and grey squirrel population, which highlights the necessity for continuous wildlife surveillance. The novel real-time PCR assay offers a highly sensitive and robust method for SqAdV-1 surveillance.
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Mathematical models for invasive species management: Grey squirrel control on Anglesey
Ecological Modelling, 2017Co-Authors: Hannah Elizabeth Mary Jones, Andrew White, Peter W. W. Lurz, Craig M. ShuttleworthAbstract:Abstract The control of invasive species and protection of threatened native species require well-developed policy and species management strategies. Mathematical models provide a key tool that can be used to test, develop and optimise strategies to manage invasive species. We use the native red squirrel and invasive grey squirrel system on the Island of Anglesey, UK, as a case study system in which to parameterise a mathematical model that includes the control of grey Squirrels. We develop a stochastic, spatial model that represents the real habitat structure, distribution and linkage on Anglesey and the neighbouring mainland and includes the key population and epidemiological dynamics of the red-grey-squirrelpox system. The model also includes a representation of the trapping and removal of grey Squirrels which is parameterised from field data on Anglesey in which grey squirrel were removed and red Squirrels reintroduced between 1998–2013. The model is used to assess different management procedures to protect red Squirrels from island re-invasion by grey Squirrels, including the threat of squirrelpox spread posed by endemic mainland grey populations. The findings have important implications for the conservation of threatened red Squirrels throughout the UK and in Europe. Moreover, the modelling framework is based on well-understood, classical models of competitive and epidemiological interactions and therefore the techniques can be adapted and applied more generally to manage the threat of invasive species in a wide range of natural systems.
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Modelling the expansion of a grey squirrel population: implications for squirrel control.
Biological Invasions, 2006Co-Authors: Clara Tattoni, Peter W. W. Lurz, Sandro Bertolino, Guido Tosi, Adriano Martinoli, Damiano Preatoni, Steven Rushton, Lucas A WautersAbstract:A recently discovered population of the North American grey squirrel (Sciurus carolinensis), introduced to\ud Ticino Park, Lombardy (N Italy), is likely to spread into continuous prealpine broadleaf forests of\ud Lombardy and the south of Switzerland. We used Spatially Explicit Population Dynamics Models (SEPMs),\ud successfully used to predict the spread of grey Squirrels in England and Piedmont, Italy, to examine\ud the effects of different control scenarios on grey squirrel expansion in a 20000 km2 area around Ticino Park.\ud Without control, grey Squirrels will invade Switzerland within the next two decades, and, concomitantly,\ud the size and distribution of local populations of native red Squirrels will be reduced. Simulating different\ud grey squirrel control or removal scenarios suggests that: (i) efficient control is possible and mainly determined\ud by the spatial distribution and woodland size of the ‘target’ control areas; and (ii) immediate actions\ud must be taken, since delay in grey squirrel control will result in the population increasing and spreading,\ud which makes the problems of successful containment more difficult. Model scenarios were based on surveys\ud that may underestimate the real distribution range and current population size of grey Squirrels. Therefore,\ud a combination of hair–tube monitoring and a public participation survey to detect grey squirrel presence,\ud which may also help to increase public awareness, is recommended. Successful containment of further grey\ud squirrel spread will require local co-operation between Italian and Swiss authorities involved in wildlife\ud managemen
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Squirrel poxvirus: Landscape scale strategies for managing disease threat
Biological Conservation, 2006Co-Authors: John Gurnell, Peter W. W. Lurz, Stephen P. Rushton, Anthony W. Sainsbury, P. F. Nettleton, Mark D. F. Shirley, C. Bruemmer, N. GeddesAbstract:Abstract Squirrel poxvirus (SQPV) is a well-documented example of pathogen-mediated competition between an invasive species, the grey squirrel ( Sciurus carolinensis ), and a native species, the Eurasian red squirrel ( Sciurus vulgaris ). SQPV causes disease with high mortality in red Squirrels but appears non-pathogenic in grey Squirrels. Not all populations of introduced grey Squirrels carry the virus, notably those in Scotland and Italy, and the rate of red squirrel replacement by grey Squirrels is some twenty times faster in those areas where grey Squirrels carry the virus. Here we develop strategies to manage the SQPV disease threat to red Squirrels by reference to the largest, designated red squirrel refuge site in England, Kielder Forest (50 000 ha). Using modelling techniques, we identify four main corridors within the buffer zone by which grey Squirrels will reach Kielder, initially within two years and in large numbers within 10 years. Assuming that greys will not settle within Kielder because of the unfavourable nature of the spruce habitat, we predict that SQPV disease will burn out at the edges of the forest, although many red Squirrels will die. This burn-out is unlikely to be the scenario in other refuge areas where the habitat is more favourable to greys. We conclude that the conservation of red Squirrels will depend on minimising contact between red and grey squirrel populations, and we advocate monitoring grey Squirrels in corridors within buffer zones around refuge areas, and removing them when detected.
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Alien species and interspecific competition: effects of introduced eastern grey Squirrels on red squirrel population dynamics
Journal of Animal Ecology, 2004Co-Authors: John Gurnell, Luc A Wauters, Peter W. W. Lurz, Guido TosiAbstract:Summary 1. Throughout much of Britain, Ireland and north Italy, red Squirrels ( Sciurus vulgaris L.) have been replaced by alien grey Squirrels ( S. carolinensis Gmelin) introduced from North America. We have studied Squirrels in two mixed woodlands in north Italy and two conifer forests in north England. In each country, one site was occupied by red Squirrels and one site by both species. 2. We have previously considered interference competition and exploitation competition for food and space between red and grey Squirrels and have showed that grey Squirrels caused reduced body growth in juvenile and subadult red Squirrels, and compete for tree seeds cached by adult red Squirrels in spring. Here we report on the effects of grey Squirrels on three fitness components in red Squirrels that have consequence at the population level: fecundity, residency and recruitment. 3. Litter production peaked in the spring and summer, but fewer females bred in the summer with grey Squirrels present. In addition, fewer individual red squirrel females produced two litters per year in the sites with grey Squirrels. Moreover, red squirrel recruitment rate and, in the mixed broadleaf sites, red squirrel juvenile residency, decreased with increasing grey squirrel density. 4. Fecundity of individual female red Squirrels was lower in red‐grey than in red-only sites because they had a lower body mass in sites with grey Squirrels. 5. Overall, there was no significant effect of grey Squirrels on residency of adult red Squirrels or on population turnover rate. However, the presence of grey Squirrels resulted in a reduction in red squirrel fitness which was evident by lower population summer breeding and a lower recruitment. Over time, this will result in a decline in population size and eventually population extinction.
