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

1. Characterising patterns of animal movement is a major aim in population
ecology, and yet doing so at an appropriate spatial-scale remains a majorchallenge. Estimating the frequency and distances of movements are of particularimportance when species are implicated in the transmission of zoonotic diseases.
2. 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 (755km231 ; 2008-2012; 1,935 capture-events; 963 badgers) to
investigate movement patterns in badgers, and undertook a comparative meta
analysis using published data from 15 European populations.
3. The dispersal movement (>1km) 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 2.6km., the upper 95%ile was 7.3km and the longest recorded
was 22.1km. 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.
4. We used a subsampling approach to demonstrate that the appropriate minimum
spatial-scale to characterise badger movements in our study population was
80km243 , 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.
5. 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.