Estimating the impact of past persecution and habitat changes on the numbers of Badgers Meles meles in Britain

Data from a Badger sett survey undertaken in the mid-1980s were used to calculate the effects of past persecution and land-use changes on Badger numbers. The current British Badger population was estimated to be 41,894 ± 4404 social groups; if the effects of past persecution were eliminated, the population could be 43,437 ± 4731 social groups, an increase of 3.7%. Most of this increase relates to persecution in Norfolk and Suffolk last century. In Britain the Badger population is largely confined to those areas which are intensively managed, and the numbers and distribution of Badgers reflect patterns of agricultural activity. However, over-intensive use of the landscape is detrimental to Badger numbers. To quantify the impact of land-use changes on the British Badger population, a number of habitat features favourable to Badgers were identified; 1-km squares that contained five or more such features had significantly higher mean Badger densities. If all the 1-km squares were managed to include five or more of the habitat features favoured by Badgers, and the effects of persecution were eliminated, the Badger population could be 58,284 ± 5640 social groups, an increase of 39%. The absence of semi-natural broadleaved woodlands in a 1-km square had the greatest effect in reducing Badger numbers, and tree-planting schemes may be beneficial in providing potential new sett sites. However, Badgers are poor colonists, and the construction of artificial setts and the translocation of displaced social groups of Badgers will greatly facilitate the colonization process. The value of such an approach for predicting the effects of future land-use policy on Badgers and other species, and for managing the British wildlife resources, is discussed.     

An analysis of some of the factors affecting the current distribution of Badger Meles meles setts in Essex

All the known Badger setts in Essex were resurveyed in the mid-1980s to record any changes in Badger distribution and status, and any associated changes in habitat and land use, during the preceding 20 years. New setts were also located. Being on the edge of London, Essex has undergone many recent changes that might be disadvantageous to Badgers. It is subjected to a high demand for land to meet increasing housing needs, intensive arable farming is widespread and few undisturbed habitats remain. These are typical of the pressures facing the Badger population in many areas of north-west Europe, and so Essex was an ideal area in which to look at the status of the Badger, and in particular the impact of human activities on a Badger population. Much of the county is unsuitable for sett construction, since it consists of London Clay and glacial tills, and the highest concentration of setts was found in the Bagshot Beds. Woodland is rare in Essex, but it was still the favoured site for sett construction. Although over half the county is devoted to arable farming, Badgers tended to avoid such areas, and also avoided close proximity to roads, particularly busy roads, for sett sites. Since much of the county is low-lying, man-made embankments were particularly important sett sites, and land-reclamation activities have probably provided additional sites for Badger setts. The effects of human activities on Badger distribution and numbers in Essex are discussed.     

Predicting Distribution and Density of European Badger (<Emphasis Type="Italic">Meles Meles</Emphasis>) Setts in Denmark

Predictive models of the spatial distribution and abundance of species based on habitat characteristics are finding increasing use in management and conservation. The European badger attracts interest as a model species both for conservation reasons and because of the important role the species is playing in understanding carnivore sociality. We developed a statistical habitat model based on presence/absence data on badger setts. To maximise the utility of the model in management, we limited the choice of model variables to those that had a clear basis in badger ecology and that could be obtained on a nation-wide digital format. We extrapolated the habitat model to a region in Denmark and developed a threshold-independent sett distribution algorithm to estimate sett densities. The habitat model was simpler than previously published models of badger sett habitat selection, but nevertheless had a predictive ability in excess of 80% judged against independent data. The sett distribution algorithm was able to simultaneously reproduce several observed patterns of sett density and distribution over the probability gradient. It thus represents a significant improvement over threshold-dependent methods used to discriminate between suitable and unsuitable habitat predicted by presence/absence regression models. Our approach demonstrates that a model of badger sett habitat suitability with high predictive power can be obtained using easily accessible map-variables and presence/absence data. This is a prerequisite for using habitat models as predictive tools over large areas. The use of a simple sett distribution algorithm circumvents the common problem of subjectively fixing a threshold to discriminate between suitable and unsuitable habitat. In conjunction the models presented here constitute an important contribution to the management of the badger in Denmark and, upon further validation, possibly to similar regions in Northern Europe.     

The past history and recent decline of Badgers Meles tneles in Essex: an analysis of some of the contributory factors

The past history of the Badger in Essex is reviewed. It is shown that the population has fluctuated in the past, and that heavy gamekeeping pressure probably reduced numbers at the turn of the century, although Badgers were probably never as rare as early recorders believed. In recent years Badgers have been rare or absent in many areas of the county because they did not afford suitable sett sites, and the county as a whole is not particularly good for Badgers. Against this already low-density Badger population, in the 20 years up to the mid-1980s, 36 % of known setts had disappeared, with agricultural activities being the major cause of sett losses, and of the remaining setts there was a 14 % reduction in the number occupied by Badgers. Also, the modal sett size was reduced from six holes to three. Direct disturbance affected nearly a quarter of all viable setts in Essex. The significance of these findings is evaluated, and the effects of changing land use, sett disturbance, Badger digging, road deaths and sub-lethal levels of agricultural chemicals on Badger numbers are discussed and quantified where possible. The possible effects of a continued fragmentation of the Badger population in Essex is reviewed. The need for further research on particular aspects of the problem, and the value of such data in understanding the population pressures facing the Badger elsewhere in Europe, are highlighted.     

Sett density as an estimator of population density in the European badger Meles meles

• 1 Estimations of European badger population density in the UK are usually based on surveys of numbers of main setts. However, this approach cannot be used in low‐density areas, such as the Mediterranean region, where no main setts can be defined. Therefore, an alternative method is needed to estimate badger density over large areas.
• 2 We reviewed the existing published information to evaluate whether badger density is correlated to the density of all setts in an area (not only the main setts) and to ask whether badger density can be predicted from total sett number throughout the geographical range of the species.
• 3 In multiple regression analysis, badger density and the size of the study area explained 73% of the variance in sett density. Badger density had a significant positive effect on sett density, while the effect of study area size was not significant. Therefore, total sett density can be used to obtain an estimation of relative badger density in all habitats and regions throughout the badger's geographical range, allowing comparative research.

     

张广才岭藏獾洞穴生境选择

2008年9月至2009年8月,在黑龙江省方正林业局新风林场,用不定宽样线法对藏獾洞穴生境选择进行研究,共记录了55组藏獾洞穴,藏獾洞口平均直径为(27.40±7.15)cm,洞深平均为(84.18±22.04)cm,倾角平均为(26.36±9.10)°,洞口总数=3.02个常用洞数+0.80个不常用洞数+0.56个废弃洞数。相对于对照样方而言,藏獾洞穴更偏爱选择位于郁闭度和植被盖度小,灌木密度大、距离近,乔木距离远,距水源和农田近、人为干扰距离远,坡度较缓的向阳中坡位的生境。资源选择函数模型为:logit(p)=246.980-1.059×植被盖度-0.703×距水源距离-1.403×坡度-45.005×坡向,模型的正确预测率为93.9%。     

Badger Meles meles setts–architecture, internal environment and function

Badger setts vary considerably in size, ranging from simple single-entrance burrows to complex tunnel systems hundreds of metres long with multiple entrances and underground chambers. Data from 19 excavated setts show that main setts are larger than other setts in terms of area and volume, and contain more chambers, nests and latrines; but setts of different sizes and types are built according to the same basic architectural principles. Little is known about the environmental conditions within setts, other than that temperature and humidity are constant in parts of a sett that are at least 7 m from the nearest entrance. Setts are used for breeding and as sleeping places and refuges, but a question remains as to the functional value of large setts. It is suggested that large main setts allow members of a social group to avoid one another underground, especially when breeding. Little is known about the use of other types of sett.     

The distribution of Eurasian badger, Meles meles, setts in a high-density area: field observations contradict the sett dispersion hypothesis

Are setts significant determinants of badger socio‐spatial organisation, and do suitable sett sites represent a limited resource, potentially affecting badger distributions? The factors determining diurnal resting den, or sett, location and selection by Eurasian badgers Meles meles L. were investigated in Wytham Woods, Oxfordshire. 279 sett sites were located. The habitat parameters that were associated with the siting of these setts were analysed and associations were sought between sett location and character and the body condition and body weight of resident badgers Habitat characteristics in the vicinity of setts were significantly different from randomly selected points. Badgers preferentially selected sites with sandy, well‐drained soils, situated on NW‐facing, convex and moderately inclined slopes at moderate altitude. There was no evidence that sett morphology (number of entrances, sett area, number of hinterland latrines) was affected by the surrounding sett site habitat characteristics. Mean body weight was significantly higher for badgers occupying territories with setts in sandy soils, situated on NW‐facing slopes, than in territories with less optimal sett characteristics. Contrary to the hypothesis that the availability of sett sites was limiting, and therefore that sett dispersion dictates the spatial and social organisation of their populations, the badgers were clearly able to excavate new setts. On our measures, these new setts were not inferior to old established ones, despite occupying subsequently exploited sites; the badgers utilising these new setts had neither lighter body weights nor poorer body condition scores. During the period of our study badgers have manifestly been able to dig numerous new setts; as satisfactory sites still remain available, this indicates that suitable sett sites have not yet become a limiting resource. There was no relationship between sett age and the characteristics of the site in which it was dug, as suitable sites were not limiting. Significantly, population expansion during the decade 1987–1997 was not constrained by lack of setts, rather the main proliferation in setts occurred after the population size had peaked in 1996. Some implications for the management and conservation of the Eurasian badger are considered.     

Predicting badger sett numbers: evaluating methods in East Sussex

Abstract. One way in which a species' numbers may be estimated without direct counting is to predict their dispersion and density from more readily available habitat measures, such as landscape variables measured from maps or vegetation variables measured in the field. We compare the power of ordination and regression techniques for predicting badger ( Meles meles L.) numbers at a local scale, using a land class system, map-read landscape variables and field-derived vegetation variables. Sett density was used as a surrogate of badger density. Multiple linear regression using vegetation and landscape variables together gave the most accurate prediction of sett density, while ordination techniques were of lesser value. The addition of vegetation variables to landscape variables did not substantially improve the power of ordination. Outlier Sett Density was predicted more accurately, and by different variables, to Main Sett Density. The relationship between badger ecology and habitat variables that were useful in predicting sett density is discussed.     

Foraging behaviour and home-range utilization in a suburban Badger (Meles tneles) population

The size and distribution of home ranges, and the dispersion of latrines, was investigated to describe the use of space and degree of territoriality within a population of Badgers ( Meles meles ) living in the suburbs of Bristol. The movement patterns of different age and sex classes were studied, along with seasonal changes in various measures of activity. Part of the study area was surveyed in detail to compare the Badger's use of space with a variety of habitat parameters, and to examine the predictability of their foraging behaviour. Many of the results are in contrast to earlier studies on rural Badgers. Range sizes were variable, and inconsistent over time, many group ranges were not contiguous and those that were overlapped. Territorial boundaries were not obvious and latrines were clumped around sett sites. Age- and sex-specific differences in movement activity were observed, along with an expansion of ranges in spring and a decrease in all forms of activity over the winter. Using multiple regression analysis, it was not easy to predict the foraging behaviour of suburban Badgers on the basis of 37 habitat variables sampled. There was some evidence of more structured foraging in the autumn, when more predictable food resources were available. The relevance of these observations to other studies on the ecology of Badger populations at varying densities and in different habitats is discussed.     

Fluctuations in the Dutch Badger Meles meles population between 1960 and 1990

The size of the Badger population in the Netherlands is estimated on the basis of sett surveys in 1960, 1970, 1980 and 1990. The numbers of used important setts were 588,640,405 and 606, respectively. So there were strong fluctuations especially due to the drop (-36%) in 1980. In 1990 the number of used important setts nearly returned to the level of 1960. However, there were important regional differences. There was a strong increase in areas with large woodlands, mainly in the central part of the country. In the south, with more traffic, farming and urbanization, the numbers remained 20–30% lower than in 1960, despite the fact that traditionally these were the best Badger areas. Only 25% of the important setts used in 1960 were still in use in 1990. The growth of the number of collapsed or lost setts increased considerably during those 30 years, indicating a rather large sett turnover probably due to disturbance or a related stress factor. Some possible causes of the fluctuations are discussed. It is recommended that a monitoring scheme be carried out every 2 or 3 years in some key areas, in order to get a better idea of the short-term fluctuation range of the population. For one-off, single-observation surveys, a simpler and more-robust sett classification is desirable, based on the number of intact holes, instead of on ‘main setts’.     

Distribution and population density of badgers Meles meles in Luxembourg

1. The distribution and density of Eurasian badgers Meles meles in Luxembourg was estimated by gathering information about the location of badger setts with a questionnaire survey, by visiting 708 setts in order to classify them as ‘main setts’ or ‘outliers’, and by estimating social group size by directly counting emerging badgers. 2. Badgers were found to be widely distributed in Luxembourg, with a minimum main sett density of 0.17 setts/km². Setts were sited preferentially in forest habitat. The mean minimum group size was 4.6 badgers. 3. The Luxembourg badger population was conservatively estimated to contain at least 2010 adult and young badgers (95% CI 1674–2347) in spring 2002, equivalent to a density of 0.78 adult and young badgers/km² (95% CI 0.65–0.91). This is moderate compared to most of continental Europe.     

Weather influences trapping success for tuberculosis management in European badgers (<Emphasis Type="Italic">Meles meles</Emphasis>)

European badgers (Meles meles) in Ireland and the UK are a reservoir for Mycobacterium bovis, the causative agent of bovine tuberculosis (TB). A number of interventions have been evaluated in attempts to control bovine TB within badger populations, and many of which rely on the capture of badgers. One strategy being implemented within Ireland is intramuscular vaccination using Bacillus Calmette-Guérin (BCG), as an alternative to badger culling. The success of vaccination as a disease control strategy depends on the ability to capture badgers and administer vaccines; thus, trapping success is crucial to effectively vaccinate the population (maximize vaccine coverage). A field vaccine trial was conducted in County Kilkenny, Ireland, from 2010–2013. We used data from this trial to evaluate the association between weather (precipitation and temperature data), badger sett characteristics, and badger trapping success. Approximately 10% of capture efforts resulted in a badger capture. Our results indicate that badger captures were the highest in drizzle, rain, and heavy rain weather conditions, and when minimum temperatures ranged from 3–8 °C. Badger captures were the highest at main setts (large burrow systems), and when sett activity scores were high (qualitative classes 4 or 5). Using local precipitation and temperature data in conjunction with observed sett characteristics provides wildlife managers with guidelines to optimize trapping success. Implementing capture operations under optimal conditions should increase the trapping success of badgers and allow for increased delivery of vaccines to manage bovine TB.     

Dynamics of tuberculosis in a naturally infected Badger population

The dynamics of bovine tuberculosis infection in a wild Badger population have been studied since 1981. Faeces are sampled regularly to determine the distribution of infection in the study area. Badgers in known infected social groups, plus the neighbouring groups, are periodically caught and subjected to full clinical and bacteriological examination to monitor the progression of infection within and between groups of Badgers. The interim results of this study are presented and discussed. During 5 years (1981–1985), the temporal spread of infection between social groups in the study area was slow and restricted. Some clinically affected Badgers have survived for long periods. Evidence of infection in individual Badgers indicates that pseudo-vertical (mother to cub) transmission may be important in the maintenance of infection in the Badger population. There is also evidence of horizontal transmission by bite wounding and aerosol infection. Badger mortality due to Mycobacterium bovis infection was low, and the prevalence of infection in male Badgers is greater than in females. The data accumulated so far show no apparent relationship between Badger population density and the prevalence of M. bovis infection, nor is there any evidence to support the hypothesis that M. bovis infection acts to depress Badger population density significantly below disease-free levels. Cattle and infected Badgers can co-exist for long periods without the disease necessarily being transmitted to cattle.     

Using the Mahalanobis distance statistic with unplanned presence-only survey data for biogeographical models of species distribution and abundance: a case study of badger setts

Aim Project‐specific data for biogeographical models are often logistically impractical to collect, forcing the use of existing data from a variety of sources. Use of these data is complicated when neither absence nor an estimate of the area sampled is available, as these are requirements of most analytical techniques. We demonstrate the Mahalanobis distance statistic (D²), which is a presence‐only modelling technique and does not require information on species absence or the sampled area. We use badger (Meles meles) setts as the basis for this investigation, as their landscape associations are well understood, and survey data exist against which to compare estimates of sett distribution and abundance. Location  England and Wales (151,403 km²). Methods We used stratified random samples of sett locations, and landscape variables that are known to be important for choice of badger sett location within a geographic information system at a cell resolution of 100 × 100 m. Landscape conditions at two scales were extracted, at and around sett locations, and the D² was used to classify all cells in England and Wales into a sett suitability model. Comparison of this sett suitability model with known main sett densities allowed estimates of main sett density to be made across England and Wales, with associated uncertainty. Results The sett suitability model was shown through iterative sampling and model evaluation using independent data to be stable and accurate. Main sett density estimates were biologically plausible in comparison with previous field‐derived estimates. We estimate 58,000 main setts within England and Wales, with 95% confidence intervals suggesting a value between 31,000 and 93,000. Main conclusions The D², which could be applied to other species and locations, proved useful in our context, where absence data were not available and the sampled area could not be reliably established. We were able to predict sett suitability across a large area and at a fine resolution, and to generate plausible estimates of main sett density. The final model provides valuable information on probable badger sett distribution and abundance, and may contribute to future research on the spatial ecology of badgers in England and Wales.     

The spatial distribution of badgers, setts and latrines: the risk for intra-specific and badger-livestock disease transmission

The spatial distribution of wildlife hosts and the associated environmental distribution of their excretory products are important factors associated with the risk of disease transmission between wildlife and livestock. At a landscape scale, heterogeneous distribution of a wildlife host will create regional hot spots for disease risk, while at the farm level, distributional patterns of wildlife excretory products as well as habitat use are of primary importance to the assessment of disease risk to livestock. In the UK, badgers have been implicated in the transmission of bovine tuberculosis to cattle. In this study, we focus on the spatial and social organization and habitat use of badgers as well as the distributions of their excretions at latrine and sett sites to assess intra- and inter-species (badger–cattle) disease risk. Across the study site, badger latrines and setts were found in prominent clusters, at distances of up to 250 and 200 m respectively. This was partly due to small-scale clustering of latrines around sett sites, so that disease risk may be higher within the vicinity of setts. The clustered distribution suggests that sites of high risk for TB transmission may be localised within farms. Exclusion of cattle from the few sett and latrine sites within their grazing pasture is therefore likely to provide an effective way of reducing the risk of disease transmission. We also found evidence of social sub-division within badger social groups based on differences in the use of main and outlier setts. This may contribute to localised clusters of infection within the badger population, resulting in heterogeneous patterns of environmental disease risk to the wider host community. A greater understanding of variation in host behaviour and its implications for patterns of disease will allow the development of more targeted and effective management strategies for wildlife disease in group-living hosts.     

Variation in resource presence, utilization and reproductive success within a population of European Badgers (Meles meles)

Variation in resource presence and resource utilization was investigated in a high density population of Badgers in Wytham Woods, Oxfordshire. Earthworms ( Lumbricus terrestris ) contributed the bulk of the diet. Differences between the diet of seven Badger groups were considerable and were most extreme during the summer. Earthworm biomass per habitat remained constant over at least 8 years, while biomass per group territory declined. Pasture fields and mature deciduous woodland (excluding beech-wood) constituted worm-rich, high quality, feeding areas. The combined relative proportion of the area of both habitats per group territory was a good predictor of total group consumption of earthworms and of the reproductive output per group, as measured by the number of independent young, while the dispersion of the two habitats determined the configuration of territories.     

Reproductive success of Tree Pipits Anthus trivialis in relation to habitat selection in conifer plantations

Aspects of the reproductive success of Tree Pipits Anthus trivialis were examined in relation to broad‐scale habitat and nest‐site selection in Thetford Forest, a coniferous plantation forest in eastern England. Three habitat classes were defined corresponding to previously reported densities of Tree Pipits: clearfell and recently planted stands (habitat class A: low density), stands 2–5 years old (B: high density) and stands 6 years or older (C: low density). The preference for 2–5‐year‐old stands indicated by higher densities was supported by the timing of territory settlement. Tree Pipits also showed distinct preferences for nest‐site characteristics that were relatively consistent across habitat classes and throughout the breeding season. At the ‘habitat scale’, results were consistent with the predictions of the ideal despotic distribution model. First clutches were laid significantly earlier in the preferred habitat class B. Overall nesting success (i.e. the proportion of nests producing fledglings), but not clutch size, also varied between habitats, being greater in habitat classes B and C than in habitat class A. The variation in overall nesting success between habitats was primarily driven by low nest survival rates during the laying/incubation period in clearfell and recently planted stands. Nest survival rates during the nestling period were lower in the preferred 2–5‐year‐old (and older) stands and declined over the course of the study. Preferences for nest‐site characteristics (at least for those that were measured) provided no apparent benefit to nest survival rates. Overall nesting success thus appeared to be determined at the habitat scale, perhaps because the broad differences in cover between habitats affected the likelihood of nest predation (the main cause of nest failure). It is suggested that the very low nesting success experienced by Tree Pipits in clearfell and new stands may be one factor in the species’ relative avoidance of this habitat and preference for 2–5‐year‐old stands.     

The role of the Badger (Meles meles) in rabies epizootiology and the implications for Great Britain

The occurrence of a wildlife rabies epizootic in Britain remains a very unlikely event, but it is important to examine all the possible consequences of such an event. Here, I examine the possible role of the European Badger (Meles meles) in such an epizootic. The population density of Badgers in Britain is much higher than that in Europe, and appears to have increased substantially over the last decade or so. The population parameters and epizootiology of rabies in the Badger are reviewed in comparison with the Fox (Vulpes vulpes) and other species. Mustelids appear to be very susceptible to rabies, with the smaller mustelids becoming aggressive, although Badgers do not appear to show heightened aggression when infected. Badger populations on the continent become severely reduced when rabies arrives in the area, and circumstantial evidence strongly suggests that Badgers can easily transmit the virus. Preliminary models support the idea that the Badger could be a very significant secondary host, especially in the initial rabies outbreak. The population recovery rate of the Badger suggests that it is unlikely to become a primary host, although short‐term epizootics in the Badger population are likely. The potential for controlling rabies in the Badger is also examined.     

Human‐modified habitats change patterns of population genetic structure and group relatedness in Peter's tent‐roosting bats

Although coloniality is widespread among mammals, it is still not clear what factors influence composition of social groups. As animals need to adapt to multiple habitat and environmental conditions throughout their range, variation in group composition should be influenced by adaptive adjustment to different ecological factors. Relevant to anthropogenic disturbance, increased habitat modification by humans can alter species’ presence, density, and population structure. Therefore, it is important to understand the consequences of changes to landscape composition, in particular how habitat modification affects social structure of group‐forming organisms. Here, we combine information on roosting associations with genetic structure of Peter's tent‐roosting bats, Uroderma bilobatum to address how different habitat characteristics at different scales affect structure of social groups. By dividing analyses by age and sex, we determined that genetic structure was greater for adult females than adult males or offspring. Habitat variables explained 80% of the variation in group relatedness (mainly influenced by female relatedness) with roost characteristics contributing the most explained variation. This suggests that females using roosts of specific characteristics exhibit higher relatedness and seem to be philopatric. These females mate with more males than do more labile female groups. Results describe ecological and microevolutionary processes, which affect relatedness and social structure; findings are highly relevant to species distributions in both natural and human‐modified environments.