Rethinking badger maps to fight bovine tuberculosis

Bovine tuberculosis (bTB), caused by Mycobacterium bovis, remains a stubborn problem for farmers and public health officials in Ireland and the UK. Part of the difficulty comes from the European badger (Meles meles), which can carry and spread the bacterium in the landscape. For years, managers have often used the location of setts — badger burrows — as a shortcut to estimate where badgers live and how many there are. That approach assumes sett presence correlates closely with badger abundance, but that assumption has rarely been tested at scale. In new work led by Virginia Morera‐Pujol, researchers used data from Ireland’s national badger culling and vaccination programme (2019–2025) to separate, or decouple, the distributions of setts and of badgers themselves. Rather than treating sett maps as a direct stand-in for animal numbers, the team applied spatial point process modelling via log-Gaussian Cox processes to look for the different environmental and human influences on where setts sit and where badgers are actually found. The study asks a simple but important question: do setts and badgers respond to the same factors, or do they tell different ecological stories?

To answer that question the researchers modelled main sett locations and badger observations as separate spatial processes, using log-Gaussian Cox processes to capture how each responded to environmental and management variables. They considered landscape features and human interventions as potential drivers. The results showed clear differences. Sett densities were linked to terrain and vegetation: elevation, slope, and proximity to forest edges emerged as key predictors of where setts concentrate. By contrast, badger densities were more strongly associated with recent culling history and the availability of pasture, suggesting that where animals are present now reflects recent management and food resources more than the physical features that determine sett placement. The modelling outputs were checked for ecological realism using independent badger body weight data, and that validation supported the idea that sett and badger patterns are governed by distinct processes. Crucially, the team found a spatial mismatch: areas with many setts were not always the same places with high badger numbers.

Those findings matter for how bTB is managed. If setts and badgers do not line up, then relying on sett locations alone could lead to misdirected surveillance, vaccination, or culling efforts, wasting resources and possibly undermining disease control. The study highlights the need for refined metrics that separate the physical footprint of setts from the current distribution of animals, and for integrating independently derived wildlife distribution models into policy decisions. For Ireland and the UK, where eradication remains the goal, this work suggests a shift toward using multiple, validated models to guide interventions — combining landscape information, recent management history, and direct measures of badger presence. By decoupling sett and badger distributions, managers can design more targeted, sustainable approaches to reduce transmission risk while avoiding assumptions that could obscure where interventions will do the most good.