BSSUB · Behaviour and social structure of urban badgers

Final Activity Report Summary - BSSUB (Behaviour and social structure of urban badgers)

In recent years, badgers (Meles meles) have become increasingly common in towns and cities. Most citizens welcome the presence of badgers but their activities cause significant problems for a minority of householders. Our project investigated the behavioural biology and ecology of urban badgers, about which little was previously known. The information obtained will contribute to a management strategy aimed at preventing or resolving conflict between the needs of urban badgers and humans. The project united three techniques. Firstly, we used radio-telemetry to investigate the ranging behaviour and habitat use of individual badgers in the city of Brighton, UK. Secondly, we used microsatellite analysis, based on remotely collected DNA, to estimate social group size, social structure, sex ratio, overall population density and average genetic relatedness in the same badger population. Thirdly, we set up a large database containing locations of badger setts in four UK towns that have relatively high badger populations, namely, Hastings, Swindon, Yeovil and Brighton. We used these data to develop a statistical model relating the presence or absence of urban badger setts to particular habitat variables. Our most striking result is that urban badger populations can achieve remarkably high densities - amongst the highest population densities of badgers recorded anywhere in the world. Social group sizes were about the same as in comparable rural areas but the home ranges of urban badgers were unusually small, enabling a large number of social groups to occupy a relatively small area. Urban home ranges were also non-contiguous (i.e., separated in space) and, in contrast to rural badgers, there was no evidence of territorial behaviour. The most likely explanation of these findings is that human residents often deliberately feed urban badgers, enabling a social group of badgers to obtain all the food that they need within a relatively small area. Microsatellite analysis indicated outbreeding at a local scale but little genetic variability within the population. This suggests, as in rural badgers, breeding of several females in some groups and a high proportion (50%) of extra-group paternity (i.e., cubs are sired by a male from a different social group). Thus, there is genetic mixing between social groups of urban badgers, despite the fact that home ranges are often isolated in space from those of neighbouring groups. As regards the wider distribution of urban badgers, several parameters contribute to predicting the presence of setts in urban environments. These include factors such as habitat type, topography and availability of cover that have been found to correlate with the presence of setts in rural areas. However, we also found that urban badgers prefer areas of intermediate human population density, possibly because these combine a sufficiently low level of disturbance (e.g., from traffic, humans and dogs) with the availability of enough householders to ensure that some will provide food. From a management point of view, our results indicate considerable potential for human-badger conflict in urban landscapes. On the other hand, even in highly urbanised areas badgers still prefer to dig burrows and forage largely in 'natural' habitat, such as wasteland and patches of scrub, rather than in gardens, which they enter primarily to take advantage of food that is deliberately provided. These findings suggest that most of the problems associated with urban badgers develop as a direct result of provisioning of badgers by human residents, which both attracts the animals into close proximity with humans and enables high population densities to build up. In the wider context of urban ecology, the results indicate the importance of small pockets of wasteland and other non-intensively used habitat for sustaining wildlife.

Data: CORDIS, © European Union