Efficacy of trapping during the initial proactive culls in the randomised badger culling trial (original) (raw)
Related papers
Impact of culling on relative abundance of the European badger (Meles meles) in Ireland
European Journal of Wildlife Research, 2012
The European Badger (Meles meles) has been implicated in the epidemiology of bovine tuberculosis in cattle populations in the Republic of Ireland. Badger populations have been subject to a culling regime in areas with chronic histories of bTB cattle herd breakdowns. Removal data from 2004 to 2010 were used to model the impact of culling on populations in areas under capture. Additionally, changes in field signs of badger activity were used as an index of abundance to support, or otherwise, the outcomes of the removal models. Significant reductions in standardised badger captures over time were found across three large study areas (total area, 1,355 km 2). Assuming that all inactive setts were vacant, an overall linear trend model suggested that badger captures had decreased by 78 % for setts with 6 years of repeated capturing operations. Given the uncertainty associated with the relationship between sett activity and badger presence, we repeated the linear modelling using two 'what if' scenarios. Assuming that individual badgers were missed on 10 % or 20 % of occasions at inactive setts, the estimated decline over 6 years is lowered to 71 % or 64 %, respectively. The decline profile consisted of a steep initial decrease in captures within the first 2 years, followed by a more gradual decrease thereafter. The number of active openings at setts (burrows) declined significantly in all three areas; but the magnitude of this decline varied significantly amongst study areas (41-82 %). There was a significant increase in the probability of setts becoming dormant with time. The removal programme was more intense (mean, 0.45 badgers culled km −2 year −1) than previous experimental badger removals in Ireland but some captures may be attributed to immigrant badgers as no attempt was made to limit inward dispersal from areas not under management. Results from this study suggest that significant reductions in badger density occurred in the areas where management had taken place. Since other nonculled badger populations in Northern Ireland and Britain exhibited stable population trends, we attribute the reduction in relative abundance to the culling regime. Further studies of the dynamics of this reduction are required to quantify how it is counteracted by immigration from populations outside of culled areas.
Factors affecting European badger (Meles meles) capture numbers in one county in Ireland
Preventive Veterinary Medicine, 2013
Understanding factors affecting the number of badgers captured at and around badger setts (burrows) is of considerable applied importance. These factors could be used to estimate probable badger densities for bovine tuberculosis (bTB) control and also for monitoring badger populations from a conservation perspective. Furthermore, badger management and vaccination programs would benefit by increasing the probability of efficiently capturing the target badger populations. Within this context, it was investigated whether badger capture numbers can be estimated from field signs and previous capture histories. Badger capture records (initial and repeated capture numbers at a sett) from a large-scale removal program (405 km(2), 643 setts) were used. Univariable count models indicated that there were a number of significant potential predictors of badger numbers, during initial capture attempts. Using a multivariable zero-inflated Poisson (ZIP) model of initial captures we found that badger capture numbers were significantly affected by sett type, season, year, and the number of sett entrances in active use. Badger capture numbers were also affected by the total previous catch during repeated capture events and by the number of previous capture attempts. There was a significant negative trend in badger captures across events. Measures of the ability of these models to estimate badger captures suggested that the models might be useful in estimating badger numbers across a population; however the confidence intervals associated with these predictions were large.
Journal of Mammalogy, 1999
Estimates of abundance of medium-to-large mammals by traditional mark-recapture models may be unreliable because quantity and quality of trapping data are low. The proposed closed-subpopulation model provides a flexible framework to increase the amount of data used for estimation of demographic parameters, by taking into account characteristics of the population and using ancillary non-trapping data. This model defines a subsection of the population that is known to be alive and within the study area during a certain period, regardless of which animals were actually caught. Population size is estimated from the proportion of animals in this closed subpopulation that were actually captured. We used this model to estimate size of a partly culled population of Eurasian badgers (Meles meles). Number of badgers included in the closed subpopulation was maximized by using data from trapping, road-traffic accidents, and radiotelemetry, and by assuming that no additions occurred to the population of young between trapping occasions. Probabilities of capture varied by season and age-class but not sex, trapping, or radio-tagging. Population estimates appeared reliable because estimated number of times individual badgers were trapped in a year corresponded with observed frequencies and estimated size of the young and adult popUlations corresponded favorably with estimates based on a mark-resight procedure.
Evaluation of indices of abundance for an unexploited badger population
The Southwestern Naturalist
We evaluated indices of relative abundance for North American badgers(Taxidea taxus) on the Rocky Mountain Arsenal, Adams Co., Colorado by comparing scent-station visitations, spotlight surveys, headlight surveys, road mortality, and a trapping index to a minimum density estimate of 0.27 badgers/km2. Live capture, although time and labor-intensive, provided a minimum relative density estimate and a trapping index to relative abundance. We captured 15 of 18 (83%) badgers during July and August 1990. Twelve of 21 (57%) captures of badgers were in traps scented with Carman's Canine Call, which may have potential for increasing capture success. If badgers are captured to estimate relative density or a trapping index, we suggest standardizing lures and seasons, and reporting if badgers were targeted or captured incidentally.
PLoS ONE, 2012
Estimates of population size and trappability inform vaccine efficacy modelling and are required for adaptive management during prolonged wildlife vaccination campaigns. We present an analysis of mark-recapture data from a badger vaccine (Bacille Calmette-Guérin) study in Ireland. This study is the largest scale (755 km 2 ) mark-recapture study ever undertaken with this species. The study area was divided into three approximately equal-sized zones, each with similar survey and capture effort. A mean badger population size of 671 (SD: 76) was estimated using a closed-subpopulation model (CSpM) based on data from capturing sessions of the entire area and was consistent with a separate multiplicative model. Minimum number alive estimates calculated from the same data were on average 49-51% smaller than the CSpM estimates, but these are considered severely negatively biased when trappability is low. Population densities derived from the CSpM estimates were 0.82-1.06 badgers km 22 , and broadly consistent with previous reports for an adjacent area. Mean trappability was estimated to be 34-35% per session across the population. By the fifth capture session, 79% of the adult badgers caught had been marked previously. Multivariable modelling suggested significant differences in badger trappability depending on zone, season and age-class. There were more putatively trap-wary badgers identified in the population than trap-happy badgers, but wariness was not related to individual's sex, zone or season of capture. Live-trapping efficacy can vary significantly amongst sites, seasons, age, or personality, hence monitoring of trappability is recommended as part of an adaptive management regime during large-scale wildlife vaccination programs to counter biases and to improve efficiencies.
The impact of sett disturbance on badger Meles meles numbers; when does protective legislation work?
Biological Conservation, 2004
Meles meles numbers have been reported from long-term studies on local populations and national surveys in Britain. One theory proposed to explain this population change, is that increased protective legislation has led to reduced levels of persecution, allowing the population to expand. In the present study, we show that the badger population in Northern Ireland has not increased in parallel with the British population, and investigate whether sustained high persecution levels are responsible. As legal protection of badgers in Northern Ireland was not increased at the same time as in Britain, a simultaneous decrease in persecution would not be expected. We test two hypotheses: (i) where there is no change in the level of sett disturbance, the number of social groups will remain unchanged and, (ii) if sett disturbance affects group size, those groups suffering from most disturbance will be smallest. We demonstrate that badger sett disturbance affects both social group size and the number of social groups, thus influencing overall badger density. We also show that high levels of sett disturbance are constraining the growth of the Northern Ireland badger population and discuss what lies behind the apparent failure of the protective legislation in this country.
2020
Summary 1. Conservation issues and a potential role in disease transmission generate the continued need to census Eurasian badgers Meles meles , but direct counts and sett counts present difficulties. The feasibility of estimating social group size and population density of badgers by quantifying their use of latrines was evaluated. 2. The number of latrines, or preferably the number of separate dung pits, which were known from bait-marking to be used by members of a social group, was positively correlated with adult group size estimated from mark-recapture studies at Woodchester Park and North Nibley (south-west England). In the latter study area both latrine-use measures were also significantly associated with total group size (i.e. including cubs and adults). 3. In spring 1997 and 1998, we quantified latrine use along strip transects, following linear features across four and five areas, respectively, in England, where badger density in summer was known from mark-recapture/resigh...
Distribution of the badger (Meles meles L.) in the Netherlands, changes between 1995 and 2001
Abstract: In 2000-2001 a national distribution survey of the badger (Meles meles) was undertaken. The survey was to contribute to the interim evaluation of the badger protection plan of the Ministry of Agriculture, Nature Management and Fisheries of the Netherlands. The execution of this protection plan started in 1984. The outcomes of this survey are presented in this article. The following aspects are described: (1) the historic development in the distribution, (2) the occupation rate of suitable badger habitat, (3) the development of settlement types, (4) the merger of subpopulations, (5) the continuity of occupation, (6) the output of translocations, and (7) the number of disappeared setts and the disturbances registered. In addition, a comparison is made with the results from the surveys of 1960, 1970, 1980, 1990 and 1995. The collected data originated mainly from fieldwork. For every 1-km square, the more than incidental use of badger setts was recorded. Earlier research (1995) on the habitat of the badger qualified 15% of the research area (about 25,000 km 2 ) as suitable. In 2001, badgers occupy about 25% of the suitable habitats available to them. The northern and eastern parts of the study area had a relatively low occupation-rate, i.e. 4 to 5 times lower than the rate for the middle and south, where the three largest populations are located. The increase of distribution in the north and east, however, was twice as much as in the middle and the south. In the Netherlands 4,400 badger setts have been recorded since 1960. During the survey more than 2,500 locations (57%) were visited. In the period 1995-2001, the distribution area of the badger increased with almost 30%. The distribution area of the nine splinter populations even increased by 48%. A decrease of 17% was recorded for the 25 dispersed populations. The average distance between the core populations existing from 1980 onwards decreased from 28 to 21 kilometres. For the period 1995-2001, in the regions of Gelderland-Veluwe and Zuid-Limburg the 18% increase in distribution area remained below the national average (29%). The large population in Gelderland-Veluwe even hardly grew (1%). The much smaller population in the Reest valley, at the border of the provinces of Drenthe and of Overijssel, did not grow at all. In the region of Gelderland-Achterhoek, the growth was minimal if the contribution from translocations is excluded. The continuity in occupation increased. Since 1960, of the 1-km squares remained occupied in the following year of survey (n=2,536). 1,402 1-km squares were at least occupied once by badgers. Of these, 257 were new in 2001, whereas 253 1-km squares remained vacant after initial occupation. Continuous occupation since 1960 occurred in 115 1-km squares. The remaining 892 1-km squares were occupied more than once, but not continuously. The three main distribution areas, Gelderland-Veluwe, Maasvallei and Zuid-Limburg, showed an increase of occupied 1-km squares of 36%. This is well above the national average of 29%. These large populations cover 84% of the badger distribution in the Netherlands. The increase must be credited almost entirely to the growth of the Meuse valley population. In the period 1990-1995, the increase of 1-km squares occupied by the three largest populations was 4% below the national average, i.e. 12%. In this period, the growth is concentrated in Zuid-Limburg. In the period 1987-2001, the translocation of badgers contributed at least 4% (37 km 2 ) to the total distribution of 2001. In this period, 210 badgers were translocated from enclosed release sites at 26 locations in seven provinces. At least 202 setts disappeared between 1995 and 2001, representing about 8% of the locations visited. One in five was occupied in 1995. The amount of destroyed setts decreased with almost 40% in comparison with the period of 1990-1995.
Exclusions for resolving urban badger damage problems: outcomes and consequences
PeerJ, 2016
Increasing urbanisation and growth of many wild animal populations can result in a greater frequency of human-wildlife conflicts. However, traditional lethal methods of wildlife control are becoming less favoured than non-lethal approaches, particularly when problems involve charismatic species in urban areas. Eurasian badgers (Meles meles) excavate subterranean burrow systems (setts), which can become large and complex. Larger setts within which breeding takes place and that are in constant use are known as main setts. Smaller, less frequently occupied setts may also exist within the social group’s range. When setts are excavated in urban environments they can undermine built structures and can limit or prevent safe use of the area by people. The most common approach to resolving these problems in the UK is to exclude badgers from the problem sett, but exclusions suffer a variable success rate. We studied 32 lawful cases of badger exclusions using one-way gates throughout England t...