The effectiveness of barriers to badger Meles meles immigration in the Irish Four Area project

Abstract

This study's objective was to estimate the permeability of barriers to badger immigration during the Irish Four Area project. These barriers were at the boundaries of removal areas, where there was proactive culling of badgers. Data from the last 3 years of the study were used. Each length of barrier was allocated a space within the removal area. These were further sub-divided into spaces of 0-2, 2-5 km and sometimes of more than 5 km from the edge of the removal area. It is assumed that all, or some, of the badgers caught within these spaces came across the barriers. The barriers were one of the following: external buffers, sea, rivers and political boundaries. The total lengths of the barriers in all areas were: external buffer 128.5 km; sea 70.9 km; river 78.6 km; political 32.2 km. We assume three scenarios: (1) all badgers caught in the final 3 years were immigrants, (2) 75% were immigrants or (3) 50% were immigrants. We test these scenarios using chi-square tests, applying internal buffers of 1 km to counter movements of badgers across zones. Using this approach and multivariate analysis, we found that the permeability of barrier types varied, with sea and external buffers being the most effective barriers. The combined capture data are further examined by the sex ratio in each range, and then the sex ratio in total. Equal numbers of males and females were found, but the source populations were probably predominantly female. If badger management options are to achieve maximum benefits, then the field effectiveness of such barriers needs to be understood.

Fine-scale landscape genetics of the American badger (Taxidea taxus): disentangling landscape effects and sampling artifacts in a poorly understood species

“…American badger's tolerance for fragmentation and overall high gene flow differs greatly from the more well-studied European badger (Meles meles) populations in the United Kingdom and Ireland. In European badgers, multiple authors have recorded evidence for restricted dispersal owing to both natural (that is, rivers; Sleeman et al, 2009;Frantz et al, 2010b) and anthropogenic (roads; Clark et al, 1998;Frantz et al, 2010a) barriers, as well as strong fine-scale IBD created by philopatry within dense populations (Pope et al, 2006;Frantz et al, 2010a). American badgers, in contrast, do not avoid large roads (Apps et al, 2002), do not form social groups and occur at lower densities than UK badger populations, so the difference in gene flow patterns likely stems from their disparate ecologies.…”

How many Eurasian badgers Meles meles L. are there in the Republic of Ireland?

“…The removal areas were separated from matched "reference areas" by rivers or other natural boundaries or buffer areas ( Fig. 1; Sleeman et al 2009). Information about variations in sett type and sett occupancy are also examined.…”

Joint Spatio-Temporal Modeling of Mycobacterium bovis Infections in Badgers and Cattle – Results from the Irish Four Area Project

“…In an area isolated by natural boundaries, the spatial process discontinues at the boundaries as noted in Henley (1981). However, there was some permeability in the FAP and limited immigration of badgers into the removal areas occurred during the study period (Griffin et al 2005;Sleeman et al 2009). Thus the problem of edge effects arises and for counties Cork, Donegal and Kilkenny this was limited to the first 2 years for the most part while in Monaghan it continued throughout the study period (Griffin et al 2005).…”

“…As stated in Kelly and More (2011), the culture method used underestimates the true infection prevalence. Badger setts are at best incompletely culled out via snare traps (Sleeman et al 2009) and thus the same sett may form part of the data for both stages 1 and 2. There is also evidence that setts are not persistently infected (or for that matter, not repopulated).…”