Large-scale movements in European badgers: has the tail of the movement kernel been underestimated?

Characterizing patterns of animal movement is a major aim in population ecology, and yet doing so at an appropriate spatial scale remains a major challenge. Estimating the frequency and distances of movements is of particular importance when species are implicated in the transmission of zoonotic diseases. European badgers (Meles meles) are classically viewed as exhibiting limited dispersal, and yet their movements bring them into conflict with farmers due to their potential to spread bovine tuberculosis in parts of their range. Considerable uncertainty surrounds the movement potential of badgers, and this may be related to the spatial scale of previous empirical studies. We conducted a large-scale mark-recapture study (755 km(2); 2008-2012; 1935 capture events; 963 badgers) to investigate movement patterns in badgers, and undertook a comparative meta-analysis using published data from 15 European populations. The dispersal movement (>1 km) kernel followed an inverse power-law function, with a substantial 'tail' indicating the occurrence of rare long-distance dispersal attempts during the study period. The mean recorded distance from this distribution was 2.6 km, the 95 percentile was 7.3 km and the longest recorded was 22.1 km. Dispersal frequency distributions were significantly different between genders; males dispersed more frequently than females, but females made proportionally more long-distance dispersal attempts than males. We used a subsampling approach to demonstrate that the appropriate minimum spatial scale to characterize badger movements in our study population was 80 km(2), substantially larger than many previous badger studies. Furthermore, the meta-analysis indicated a significant association between maximum movement distance and study area size, while controlling for population density. Maximum long-distance movements were often only recorded by chance beyond the boundaries of study areas. These findings suggest that the tail of the badger movement distribution is currently underestimated. The implications of this for understanding the spatial ecology of badger populations and for the design of disease intervention strategies are potentially significant.

An assessment of injury to European badgers (meles meles) due to capture in stopped restraints.

As part of ongoing culling operations, European badgers (Meles meles) were captured using stopped restraints in winter (October to December 2005) and summer (May to June 2006) in the Republic of Ireland. A subset of these badgers, those caught during four consecutive nights, was examined postmortem to determine the frequency and severity of physical injuries resulting from capture in the restraints. The skin and the tissues underlying the restraint of 343 badgers were assessed for injury by visual examination. There was an absence of skin damage or only minor skin abrasions in 88% of badgers; an absence of subcutaneous tissue injury or only localized subcutaneous tissue injury in 69%; and an absence of muscle injury or only slight muscle bruising in 99% of badgers. Only 2% of badgers had cuts to the skin and 5.5% had extensive subcutaneous edema, whereas 1.2% had areas of hemorrhage and tearing of the underlying muscle. Our results show that the majority of badgers examined sustained minimal injuries attributable to capture in stopped restraints.

The importance of 'neighbourhood' in the persistence of bovine tuberculosis in Irish cattle herds.

Local persistence of infection is a key feature of bovine tuberculosis (bTB) among cattle herds in the Republic of Ireland. The aim of this study was to determine the relative importance of 'neighbourhood', specifically farm-to-farm spread and spread from wildlife, in the persistence of bTB by investigating herds having a bTB episode in 2006. A case-control study was conducted on the association between the occurrence of a bTB episode in 2006 and the occurrence of bTB in previous years among neighbouring herd(s) within 1 km, while controlling for each herd's bTB history and other risk factors. Neighbouring herds were grouped into three zones, based on distance, and bTB incidence measures summarised within each zone and by calendar year (2001-2005). The incidence of bTB was associated with an increased animal incidence in two subsets of neighbouring herds: (i) herds directly contiguous during the previous 2 years (attributable fraction=0.20), and (ii) herds at a distance of >25 m in the previous year (attributable fraction=0.19). Other predictors of bTB in a herd in 2006 included the occurrence of a bTB episode within that herd in any of the previous 5 years, herd size, and the number of animals purchased at age greater than 12 months. An infected wildlife source best explains the existence of a "neighbouring herd risk" for bTB at distances greater than 25 m. Further studies will be necessary to determine to what extent neighbouring herd risk within 25 m may be confounded by the same wildlife (badger) source.