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Peter W. W. Lurz - One of the best experts on this subject based on the ideXlab platform.
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integrating Red Squirrel sciurus vulgaris habitat requirements with the management of pathogenic tree disease in commercial forests in the uk
Forest Ecology and Management, 2012Co-Authors: Craig M Shuttleworth, Peter W. W. Lurz, Neville Geddes, John BrowneAbstract:Abstract The native Red Squirrel is being replaced by the introduced North American eastern grey Squirrel in the UK. Here, Sitka spruce dominated plantations containing a larch and pine element offer the best long-term opportunity to conserve the Red Squirrel because they can sustain populations in a forest environment where the competitive advantage of the grey Squirrel is Reduced. Forest habitat management in designated stronghold areas in England and Scotland is therefore a key strategy for Red Squirrel conservation. However, the threat of pathogenic tree disease is already leading to changes in forest composition through modified thinning and planting regimes. This has the potential of not only altering habitat suitability for Red Squirrels but also the competitive ability of grey Squirrels. For example, Phytophthora ramorum can severely affect Japanese larch, whilst other common crop species such as Corsican pine, Scots pine and lodgepole pine are all vulnerable to Red Band Needle Blight (Dothistroma septosporum); factors driving significant changes in future forest composition. In this paper we wish to highlight the serious impact of these diseases on established Red Squirrel management options. We examine proactive and reactive management in three case studies which are attempting to integrate Red Squirrel habitat requirements into evolving tree disease management protocols. We recommend specific tree species that are both less susceptible to infections and offer potential alternative seed sources for Red Squirrels, whilst stressing the need for research into grey Squirrel exploitation of such crops. We also highlight how the presence of grey Squirrels is limiting the use of hazel and other broadleaved species in this context. Finally, a flexible Red Squirrel management protocol is presented to assist forest managers to integrate Red Squirrel conservation with the threat posed by Red Band Needle Blight and P. ramorum.
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disease threats posed by alien species the role of a poxvirus in the decline of the native Red Squirrel in britain
Epidemiology and Infection, 2006Co-Authors: S P Rushton, Peter W. W. Lurz, John Gurnell, P. F. Nettleton, Mark D. F. Shirley, C. Bruemmer, A W SainsburyAbstract:Red Squirrels are declining in the United Kingdom. Competition from, and Squirrel poxvirus (SQPV) disease carried by, grey Squirrels are assumed to be determining the decline. We analyse the incidence of disease and changes in distribution of the two species in Cumbria, from 1993 to 2003 and compare these to the pRedictions of an individual-based (IB) spatially explicit disease model simulating the dynamics of both Squirrel species and SQPV in the landscape. Grey Squirrels increased whilst Red Squirrels declined over 10 years. The incidence of disease in Red Squirrels was related to the time since grey Squirrels arrived in the landscape. Analysis of rates of decline in Red Squirrel populations in other areas showed that declines are 17–25 times higher in regions where SQPV is present in grey Squirrel populations than in those where it is not. The IB model pRedicted spatial overlap of 3–4 years between the species that was also observed in the field. The model pRedictions matched the observed data best when contact rates and rates of infection between the two species were low. The model pRedicted that a grey Squirrel population control of >60% effective kill was needed to stop the decline in Red Squirrel populations in Cumbria.
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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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patterns of genetic diversity in the Red Squirrel sciurus vulgaris l footprints of biogeographic history and artificial introductions
Conservation Genetics, 2004Co-Authors: Marie L Hale, Peter W. W. Lurz, Kirsten WolffAbstract:British S. vulgaris are classified as aseparate subspecies, S. v. leucourus, tomainland Europe. While S. vulgaris is notunder threat across most of its Eurasian range,in Britain, Ireland and Italy populations aRedeclining, mainly due to the introduction ofthe American grey Squirrel (S.carolinensis). In this study, we conducted anextensive survey of mitochondrial DNA variationin British S. vulgaris populations and apreliminary survey of continental Europeanpopulations. Our main aims were to determinethe extent to which any populations of S.vulgaris in Britain are partially or whollythe product of artificial translocation of RedSquirrels from continental Europe, and whethercontinental population variation will provideinformation on post-glacial reafforestationpatterns in Europe. We found that the majorityof extant populations of British S.vulgaris are of continental ancestry, manywith a very recent (last 40 years) Scandinavianancestry. The Scandinavian haplotype hasrapidly become the most dominant innortheastern Britain, despite not appearing innorthern English populations until 1966. Thissuggests that these Squirrels may have anadaptive advantage in the non-native sprucedominated conifer plantations of northernEngland. Our preliminary examination ofcontinental populations demonstrated that theyare sufficiently differentiated to allow aphylogeographic study of this species.
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morphological changes in a british mammal as a result of introductions and changes in landscape management the Red Squirrel sciurus vulgaris
Journal of Zoology, 2003Co-Authors: Marie L Hale, Peter W. W. LurzAbstract:British Red Squirrel populations have been subject to landscape management practices resulting in large-scale fragmentation and defragmentation of habitat, as well as numerous historical introductions of closely related subspecies. This unique population history allowed us to examine: (1) the morphological changes to a rare native species probably caused by hybridization with introduced subspecies; (2) the impact of landscape management, specifically reforestation, on the spread of these morphological changes across the north of England. British Red Squirrels represent a peripheral population of Sciurus vulgaris, which is regarded as a separate subspecies (S. v. leucourus) to populations found on the European continent. British populations are in danger of extinction because of the introduction of the North American grey Squirrel S. carolinensis. Repeated translocation of continental European S. vulgaris individuals to Britain over 150 years may be responsible for an alteration of the morphological characteristics of populations compaRed to the original subspecies description. The majority of examined populations possessed the coat colour characteristics associated with continental European subspecies. Only populations in the western region of Cumbria possessed coat colour characteristics similar to the described subspecies S. v. leucourus. Changes to landscape connectivity in Britain during the 1980s greatly alteRed dispersal patterns, resulting in an increase of gene flow from populations in the north-east of England and the Borders into Cumbria. The morphological characteristics of the Cumbrian population also changed over this period, from traits similar to the British subspecies before 1980, to traits similar to the continental European subspecies after 1980. This study demonstrates the threat landscape management practices and the introduction of closely related subspecies can present to rare peripheral populations.
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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disease threats posed by alien species the role of a poxvirus in the decline of the native Red Squirrel in britain
Epidemiology and Infection, 2006Co-Authors: S P Rushton, Peter W. W. Lurz, John Gurnell, P. F. Nettleton, Mark D. F. Shirley, C. Bruemmer, A W SainsburyAbstract:Red Squirrels are declining in the United Kingdom. Competition from, and Squirrel poxvirus (SQPV) disease carried by, grey Squirrels are assumed to be determining the decline. We analyse the incidence of disease and changes in distribution of the two species in Cumbria, from 1993 to 2003 and compare these to the pRedictions of an individual-based (IB) spatially explicit disease model simulating the dynamics of both Squirrel species and SQPV in the landscape. Grey Squirrels increased whilst Red Squirrels declined over 10 years. The incidence of disease in Red Squirrels was related to the time since grey Squirrels arrived in the landscape. Analysis of rates of decline in Red Squirrel populations in other areas showed that declines are 17–25 times higher in regions where SQPV is present in grey Squirrel populations than in those where it is not. The IB model pRedicted spatial overlap of 3–4 years between the species that was also observed in the field. The model pRedictions matched the observed data best when contact rates and rates of infection between the two species were low. The model pRedicted that a grey Squirrel population control of >60% effective kill was needed to stop the decline in Red Squirrel populations in Cumbria.
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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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conserving Red Squirrels sciurus vulgaris mapping and forecasting habitat suitability using a geographic information systems approach
Biological Conservation, 2002Co-Authors: John Gurnell, Peter W. W. Lurz, Mark D. F. Shirley, Michael J Clark, S P RushtonAbstract:A model of habitat suitability linked to a Geographic Information System was developed for the Red Squirrel (Sciurus vulgaris) in 2800 ha of Thetford Forest, East England, to assess Red Squirrel population numbers in relation to forest management. We defined each forest sub-compartment or parcel of land in terms of its tree species and age between 1995 and 2015, and categorised each parcel of land as low, moderate or high Red Squirrel suitability. Resident Squirrels may live in more than one habitat patch providing the distance between patches is within the foraging range of the animals and the land between the patches does not act as a barrier to foraging movements. Moreover, Squirrels require a minimum area (home range area) of suitable habitat that will provide them with sufficient food resources. To examine these two factors, we exploRed 120 different model scenarios using three different distances to link patches together and four different sized minimum areas, termed minimum linked areas (MLA), that would hold resident Red Squirrels, at five year intervals between 1995 and 2015. As an overall measure of suitability, we summed all the MLAs in the reserve for high plus moderate suitability, which we have called the total linked area (TLA), and forecast how this may change in the future. We show that TLA will increase from 39% in 1995 to 67% of the study area by 2015, demonstrating that the reserve will get better for Red Squirrels over this time. We also demonstrate how changes in forest management would further increase TLA to 82% by 2015. Our results demonstrate how a habitat suitability model operating at the scale of an individual forest, coupled with a GIS and based on an understanding of the species' ecology, provides an objective way of assessing the impact of forest management prescriptions on Red Squirrel populations.
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parapoxvirus causes a deleterious disease in Red Squirrels associated with uk population declines
Proceedings of The Royal Society B: Biological Sciences, 2002Co-Authors: Daniel M Tompkins, A W Sainsbury, P. F. Nettleton, D Buxton, John GurnellAbstract:The disease implications of novel pathogens need to be consideRed when investigating the ecological impact of species translocations on native fauna. Traditional explanations based on competition or pRedation may often not be the whole story. Evidence suggests that an emerging infectious disease, caused by a parapoxvirus, may be a significant component of the impact that the introduced grey Squirrel has had on UK Red Squirrel populations. Here we validate the potential role of parapoxvirus by proving that the virus is highly pathogenic in the Red Squirrel while having no detectable effect on grey Squirrel health.
Lucas A. Wauters - One of the best experts on this subject based on the ideXlab platform.
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will an ancient refuge become a modern one a critical review on the conservation and research priorities for the Red Squirrel sciurus vulgaris in the iberian peninsula
Hystrix-italian Journal of Mammalogy, 2014Co-Authors: Rita Gomes Rocha, Lucas A. Wauters, Maria Da Luz Mathias, Carlos FonsecaAbstract:Mediterranean peninsulas are well-known glacial refugia for several mammal species. For Eurasian Red Squirrel ( Sciurus vulgaris ), a forest-dwelling rodent, there is some evidence that population diversification was influenced by these refugia. Here, we review the poorly known history of the Red Squirrel in the Iberian Peninsula, and discuss current threats to this species, suggesting conservation guidelines and exploring several research lines for forthcoming studies. Red Squirrel populations suffeRed several bottlenecks in Iberia, but recently, after four centuries of absence, this species is expanding throughout the Portuguese territory. Although S. vulgaris taxonomic and genetic status needs further investigation, molecular data support the occurrence of a possible distinct cluster in the Iberian Peninsula. Additionally, a distinct and endemic population was recorded to the Sierra de Espuna, in Spain, which was probably the result of Quaternary climatic and vegetation fluctuations. Two major threats for Red Squirrels in Europe were identified: (i) habitat deterioration; and (ii) competition with the invasive Eastern grey Squirrel ( S. carolinensis ). Conservation actions should focus on the conservation, restoration and appropriate management of suitable forested habitats. Although to date no grey Squirrels occur in the wild in the Iberia, the trade and release of this invasive sciurid species is already forbidden by national conservation agencies in both Iberian countries and awareness campaigns are suggested. An integrated research approach using both molecular and ecological data, and a large dataset containing samples from the entire Iberian Peninsula, should be followed to better understand historical, contemporary and future factors that may affect Squirrel distribution. Download the complete issue.
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a grey future for europe sciurus carolinensis is replacing native Red Squirrels in italy
Biological Invasions, 2014Co-Authors: Sandro Bertolino, Damiano Preatoni, Lucas A. Wauters, Nicola Cordero Di Montezemolo, Adriano MartinoliAbstract:Introduced mammals can cause extinction of native species due to replacement competition, disease, pRedation or hybridization. We studied the colonization of Piedmont (NW-Italy) by American grey Squirrel (Sciurus carolinensis) and its effect on the native Red Squirrel (Sciurus vulgaris). Presence/absence data (2 × 2 km2), of both species were (re)constructed using questionnaires, literature, existing databases, unpublished information, and direct monitoring with hair-tubes. In 1970 Red Squirrels were still widespread and greys were restricted to forests near the introduction site. By 1990, grey Squirrels had increased their range to 220 km2, which coincided with the disappearance of native Squirrels from 33 squares inside this range. The invasive species continued its spread occupying an area of 2,016 km2 in 2010; within this area Red Squirrels went extinct in 88 squares. Overall, from 1970 to 2010 Red Squirrel went extinct in 62 % of 2 × 2 km2 (ca. 1,689 km2), and were replaced by grey Squirrels. The spread of the alien species was slow in the first 20 years, but doubled in the successive two decades. Nevertheless spread was slower than in Ireland and England. Grey Squirrel adapt to climate and habitats in both North and South Europe, causing extinction of the native Red Squirrel. A EU LIFE co-funded project with the aim to control the grey Squirrel in North Italy and recent trade-restrictions and trade-ban are a first step in Reducing the risk of grey Squirrels invading other countries, but their effectiveness will have to be evaluated.
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Macroparasite community of the Eurasian Red Squirrel (Sciurus vulgaris): poor species richness and diversity.
Parasitology research, 2013Co-Authors: Claudia Romeo, Adriano Martinoli, Lucas A. Wauters, Benoît Pisanu, Nicola Ferrari, Franck Basset, Laurent Tillon, Nicola Saino, Jean-louis ChapuisAbstract:The Eurasian Red Squirrel (Sciurus vulgaris) is the only naturally occurring tree Squirrel throughout its range. We aim at improving current knowledge on its macroparasite fauna, expecting that it will have a poor parasite diversity because in species that have no sympatric congeners parasite richness should be lower than in hosts sharing their range with several closely related species, where host-switching events and lateral transmission are promoted. We examined gastro-intestinal helminth and ectoparasite communities (excluding mites) of, respectively, 147 and 311 Red Squirrel roadkills collected in four biogeographic regions in Italy and France. As expected, the macroparasite fauna was poor: we found five species of nematodes and some unidentified cestodes, three fleas, two sucking lice and two hard ticks. The helminth community was dominated by a single species, the oxyurid Trypanoxyuris (Rodentoxyuris) sciuri (prevalence, 87 %; mean abundance, 373 ± 65 worms/host). Its abundance varied among seasons and biogeographic regions and increased with body mass in male hosts while decreased in females. The most prevalent ectoparasites were the flea Ceratophyllus (Monopsyllus) sciurorum (28 %), whose presence was affected by season, and the generalist tick Ixodes (Ixodes) ricinus that was found only in France (34 %). All the other helminths and arthropod species were rare, with prevalence below 10 %. However, the first record of Strongyloides robustus, a common nematode of North American Eastern grey Squirrels (S. carolinensis), in two Red Squirrels living in areas where this alien species co-inhabits, deserves further attention, since low parasite richness could result in native Red Squirrels being particularly vulnerable to parasite spillover.
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scale dependent environmental variables affecting Red Squirrel sciurus vulgaris meridionalis distribution
Italian Journal of Zoology, 2010Co-Authors: P.c. Rima, M. Cagnin, Gaetano Aloise, Damiano Preatoni, Lucas A. WautersAbstract:We investigated the effects of habitat fragmentation on the endemic subspecies of Red Squirrel Sciurus vulgaris meridionalis in the Pollino National Park, Calabria, Southern Italy. Presence/absence of Squirrels was monitoRed using drey (nest) counts in 51 1‐ha census plots. Squirrel dreys were found in 16 plots (31%). Patch size was not correlated to Squirrel presence. Squirrels were found in patches ranging from 3.19 to 6051 ha. Small‐scale forest structure significantly affected the probability of occurrence. The proportion of conifers and average tree height positively pRedict Squirrel presence; furthermore, nest density was positively correlated with high tree species diversity and the proportion of deciduous oaks (Quercus cerris, Q. ilex). Also at the home‐range scale the proportion of conifer forest and oak‐dominated deciduous forests positively pRedicted Squirrel presence (200–300 m radius). At the even larger scale, corresponding with potential dispersal distances (3000 m radius), landscape parame...
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effects of spatio temporal variation in food supply on Red Squirrel sciurus vulgaris body size and body mass and its consequences for some fitness components
Ecography, 2007Co-Authors: Lucas A. Wauters, Sandro Bertolino, Marleen Vermeulen, Stefan Van Dongen, A Molinari, Guido Tosi, Erik MatthysenAbstract:Food availability is likely to influence body condition and, in turn, fitness. The intensity of this response may vary between populations of the same species on a small spatial and temporal scale. We used 5 yr of data from 6 Eurasian Red Squirrel Sciurus vulgaris populations from the southern Alps to explore differences in body size and body mass among neighbouring populations, in relation to habitat type and variation in food supply. We also investigated sexual dimorphism in these traits and whether phenotypic variation affects local survival and female reproductive success. Mean hind foot length, a measure of body size, did not differ between sexes but diffeRed between areas. Seasonal variation in body mass was small with no evidence for fattening in autumn. Females were slightly heavier than males, but this difference was largely explained by mass gain of females during reproduction. The size of conifer seed crops, the major food supply, varied strongly over years and between habitats, but this variation corresponded only weakly with autumn body mass. Differences in size and mass between populations were partially explained by habitat-related differences in body size and variability of seed-crops, suggesting differential selection for smaller Squirrels in spruce-larch forests against selection for larger and heavier animals in mixed broadleaves and conifer forests and in Scots pine forests with more stable seed production. The probability of reproduction by females increased with body mass, but varied strongly between habitats and years, with more females reproducing in years with rich seed-crops. In both sexes, body mass positively affected probability of settlement and length of residency. Our results suggest that in temporally variable environments that differ in overall amount of food resources, individual variation in body mass is related to habitat type, and that having a relatively high body mass, within each population, positively affects male and female settlement success and local survival, and female reproductive success.
Erik Matthysen - One of the best experts on this subject based on the ideXlab platform.
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effects of spatio temporal variation in food supply on Red Squirrel sciurus vulgaris body size and body mass and its consequences for some fitness components
Ecography, 2007Co-Authors: Lucas A. Wauters, Sandro Bertolino, Marleen Vermeulen, Stefan Van Dongen, A Molinari, Guido Tosi, Erik MatthysenAbstract:Food availability is likely to influence body condition and, in turn, fitness. The intensity of this response may vary between populations of the same species on a small spatial and temporal scale. We used 5 yr of data from 6 Eurasian Red Squirrel Sciurus vulgaris populations from the southern Alps to explore differences in body size and body mass among neighbouring populations, in relation to habitat type and variation in food supply. We also investigated sexual dimorphism in these traits and whether phenotypic variation affects local survival and female reproductive success. Mean hind foot length, a measure of body size, did not differ between sexes but diffeRed between areas. Seasonal variation in body mass was small with no evidence for fattening in autumn. Females were slightly heavier than males, but this difference was largely explained by mass gain of females during reproduction. The size of conifer seed crops, the major food supply, varied strongly over years and between habitats, but this variation corresponded only weakly with autumn body mass. Differences in size and mass between populations were partially explained by habitat-related differences in body size and variability of seed-crops, suggesting differential selection for smaller Squirrels in spruce-larch forests against selection for larger and heavier animals in mixed broadleaves and conifer forests and in Scots pine forests with more stable seed production. The probability of reproduction by females increased with body mass, but varied strongly between habitats and years, with more females reproducing in years with rich seed-crops. In both sexes, body mass positively affected probability of settlement and length of residency. Our results suggest that in temporally variable environments that differ in overall amount of food resources, individual variation in body mass is related to habitat type, and that having a relatively high body mass, within each population, positively affects male and female settlement success and local survival, and female reproductive success.
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does matrix resistance influence Red Squirrel sciurus vulgaris l 1758 distribution in an urban landscape
Landscape Ecology, 2003Co-Authors: Goedele Verbeylen, Luc De Bruyn, Frank Adriaensen, Erik MatthysenAbstract:In determining isolation effects in fragmented populations, the landscape matrix is not often consideRed. Usually simple distance measures are used to quantify degree of isolation. We tested the effect of the matrix on the presence of Red Squirrels in 354 wooded patches in the Brussels Region, by comparing several isolation measures. These were 1) distance to the nearest source patch, 2) the Hanski-measure (a combination of distance to and size of all possible sources), 3) effective distances calculated from different least cost models using the ArcView grid extension ‘Cost Distance’ (a combination of distance and resistance of the landscape, with different resistances for different landscape types) and 4) some combinations of the Hanski-measure and the effective distances. Size and quality of the target patches were always included in the tests of the pRedictive power of different isolation measures on Squirrel presence/absence. All variables examined (patch size, quality and isolation) significantly influenced Squirrel presence. Models using the effective distances gave the best results. Models including the Hanski-measure improved significantly when Euclidean distance was replaced by effective distance, showing that parameterisation of matrix resistance added significant additional explanatory power when modelling Squirrel presence.
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patch occupancy population density and dynamics in a fragmented Red Squirrel sciurus vulgaris population
Ecography, 2003Co-Authors: Goedele Verbeylen, Luc De Bruyn, Erik MatthysenAbstract:We studied population dynamics of Red Squirrels in a group of small forest fragments, that cover only 6.5% of the total study area (4664 ha) and where distances to the nearest source population were up to 2.2 km. We tested effects of patch size, quality and isolation and supplementary feeding on patch occupation during 1995-99. Larger patches and patches with supplementary feeding had a higher probability of being occupied. No patch < 3.5 ha was ever occupied. No effects of isolation were found, suggesting that the forest habitat in the study area is not sufficiently fragmented to influence Red Squirrel distribution across patches. For medium sized patches (3.7-21 ha), that were occupied some years, there was an increase in patch occupation over the years, even though overall population size tended to decrease. These patches had a high turnover, especially of males. Patches in which the Squirrel population went extinct were recolonized within a year. For patches that were at least some years occupied. Squirrel density depended on patch quality only. No effects of patch size isolation and winter temperature on population density were found. These data suggest that in our study area habitat fragmentation has no effect on local Squirrel density and that the random sample hypothesis explains the distribution pattern across patches.
Henrik Andrén - One of the best experts on this subject based on the ideXlab platform.
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Effects of habitat fragmentation on Eurasian Red Squirrel (Sciurus vulgaris) in a forest landscape
Landscape Ecology, 1999Co-Authors: Annika Delin, Henrik AndrénAbstract:We studied the effects of habitat fragmentation, measuRed as forest stand size and isolation, on the distribution of Eurasian Red Squirrels (Sciurus vulgaris). Squirrel density was surveyed during four years in 46 forest stands (0.1–500 ha) in a forest landscape in south-central Sweden. The only factor that significantly influenced a density index was the proportion of spruce within a habitat fragment. Neither fragment size nor degree of isolation were significant. Furthermore, none of the interactions with year were significant, suggesting the same pattern in all four years. Thus, the effect of habitat fragmentation in this study seems to be only pure habitat loss, i.e. halving the proportion of preferRed habitat in the landscape should result in a halving of the Red Squirrel population. Therefore, the landscape can be viewed as functionally continuous for the Squirrels, although the preferRed habitat was divided into fragments. The most likely explanation for the difference between this study and other studies on Squirrels that found effects due to habitat fragmentation is a combination of shorter distances and less hostile surroundings in our study area. To identify landscape effects requires multiple studies because single studies usually consider only one landscape.
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habitat selection in the eurasian Red Squirrel sciurus vulgaris in relation to forest fragmentation
Oikos, 1994Co-Authors: Henrik Andrén, Annika DelinAbstract:A population of Eurasian Red Squirrels (Sciurus vulgaris) in south-central Sweden showed a strong preference for forest older than 35 years and with more than 25% Norway spruce (Picea abies). This preferRed habitat constituted 24% of the study area. The proportion of avoided habitats was 30%, and the remaining 46% could be described as used but not preferRed habitats. Given these proportions, the Squirrels can be shown theoretically to be able to reach all preferRed patches by moving across the used, although not preferRed habitat patches, or within the preferRed ones. Males had larger home ranges (mean 121.6 ha) than females (mean 23.0 ha). Mean daily movement was 430 m for males and 180 m for females; the maximum movement was 2800 m for males and 680 m for females. Most of the preferRed habitat occurRed in fragments larger than the area requirement of an individual Squirrel, and even the most isolated fragments were within a trivial range for Squirrels. Therefore, we pRedict that the random sample hypothesis will give a good pRediction of the effects of forest fragmentation on the Red Squirrel in this landscape. However, if the proportion of avoided habitats increases, isolation and fragment size might affect the population density of Red Squirrels and the population size would be smaller than pRedicted from the random sample hypothesis.