Badger Programme

CONSERVATION CONTEXT

Threats facing species such as changing landscapes and climate change are often seen at the scale of populations and species by the time their impacts are considered a concern for conservation. However, ultimately it is how individuals respond to changing habitat conditions or climate change, and how their responses ramify through their society, that reveal insights necessary to understand the processes underlying these threats, and therefore how we might go about tackling them.

The Badger Project has proven invaluable in collecting a wealth of fundamental life history data on the badgers of Wytham Woods and beyond for 35 years, providing a model for behaviour, ecology and evolution. The unprecedented detail of our records now enable us to formulate a truly comprehensive understanding of badger socio-ecology, where the generalist badger provides a model on how other species may respond to the challenges they face.

APPROACH

Badger trapping

Since 1987, we have undertaken 3-4 systematic trap – release sessions each year at Wytham Woods. We catch badgers in specially designed traps, set over-night and checked each morning. Captured animals are then sedated to enable us to weigh, measure and sample them before being returned to their site of capture. Any animal new to our regime is given a unique identifying tattoo (usually as a cub), allowing us to track life-histories individually thereafter. Crucially, we take a small blood sample, which provides DNA for a wide range of genetic analyses, as well as supporting studies on hormones, diseases and immunological responses. A proportion of badgers are also occasionally fitted with tracking devices to enable us to follow their movement patterns. Throughout we have carefully attended to the welfare of our study badgers, both from an ethical standpoint, and also to minimize disruption of their natural behaviour. For this purpose we have pioneered blood tests for measuring physiological stress that have proved useful not only for badgers, but also for other wildlife, and even to monitor the stress levels of athletes and executives.

Badger society

Our understanding of badger society has important implications for how badgers re-organise their society after management interventions, such a TB culling or sett closures for development. Our work on badger social behaviour has revolutionised understanding of how badgers interact with each other both within and between groups. Our tracking approach started with conventional VHF and GPS systems, and we developed active RFID location tags (security tags detected by base-stations in the field). We then invented a magneto-inductive underground tracking system, in collaboration with Prof. Andrew Markham at Oxford University’s Department of Computer Science. This new technology transformed our understanding of the activity within badger setts underground. For instance, badgers don’t simply forage through the night, but return for a nocturnal ‘siesta’, using peripheral, shallow chambers, whereas they use deeper chambers by day. This technique has also led to our understanding that badgers in different body-condition exhibit different activity budgets in relation to prevailing weather. Our video-surveillance has revealed grooming partners, and how badgers anoint themselves with subcaudal gland secretions. We found that badger latrines act as social media sites, where information is exchanged, but do not provide hard borders to territories. Ultimately we find that badger setts are not exclusive breeding cliques, nor do members engage in any substantive cooperative behaviour. Instead it seems they are simply groups of individuals acting as they might at low density, but forced together to co-share a common subterranean den.

Badgers and TB

The involvement of badgers in the transmission of bovine tuberculosis (bTB) in cattle in the UK, and attempts to control the disease in cattle by killing badgers, has been among the most controversial issues in wildlife disease management globally. Our research on badgers in Wytham Woods and rural landscapes in Gloucestershire and Wiltshire, led to the perturbation hypothesis, and documented the individual behavioural responses of badgers in populations subjected to culling, and interpreted these in the context of a large-scale experiment, the randomized badger control trial (RBCT). The evidence for perturbation is strong, and provides both an explanation for why attempts to control bTB in cattle by killing badgers have generally been unsuccessful, and why they continue to be unpromising. David Macdonald was invited by the Badger Trust to write a commentary in their report ‘Tackling Bovine TB Together: Towards Sustainable, Scientific and Effective bTB Solutions’

Genetics and mate choice

Most recently in 2022, a badger genome was created by the Wellcome Sanger Institute (Darwin Tree of Life Project) using blood samples of three of our study animals from Wytham Woods, an individual badger plus both of its parents. This reference genome allows new exploration in evolutionary ecology and genetics, such as the effect of climate change in wildlife populations at a molecular level. By combining the vast amount of badger population data with the new reference genome, we start to answer intricate questions such as whether early-life adversity affects individual badgers in later life and whether this is linked to epigenetic patterns, where gene expression is affected by environmental factors rather than altering the genetic code itself.

Until the early 2000s, assigning parentage to badgers and establishing a genealogy, was impossible due to the coarseness of genetic fingerprinting techniques available at that time. Later, advances using ‘microsatellites’ (a detailed form of genetic fingerprinting), allowed us to piece together the population family tree, which revealed unexpectedly high levels of extra-group paternity in this population. We also found that while they avoid inbreeding, they are otherwise not picky about mate choice. Combining genetics with immunology, we explored whether in badgers the ‘Major Histocompatibility Complex’ (MHC) plays a part in mate choice selection. The genetic diversity attainable through out-breeding was expected to be beneficial to the ability of individuals to resist internal parasites and infections, yet this too proved to be far from clear-cut, with certain MHC genes conferring an advantage against certain pathogens.