The impact of roadworks on the ranging behaviour of European badgers (Meles meles)

Abstract

The European badger (Meles meles), one of Ireland’s most iconic native species, acts as a wildlife reservoir of Mycobacterium bovis, the causative agent of tuberculosis in cattle. Badgers have been implicated in the spread of the disease to cattle in Ireland and the UK. To understand the dynamics of a disease and to control it successfully, a complete picture of ranging behaviour of the carrier species is required. Much of our knowledge of ranging behaviour in badgers derives from studies of high-density populations. There is concern that environmental disturbances, such as major roadworks, can increase movements between badger social groups, resulting in increased TB breakdowns in cattle herds. The ranging of a medium-density Irish badger population was monitored before, during and after a major road upgrade and realignment project, using GPS tracking collars. Using the GPS data, I estimated badger home range size, nightly distances travelled and the distance and frequency of extra-territorial excursions. My results show that the road upgrade and realignment project had a very limited effect on the ranging behaviour of badgers, and that territoriality in the area was not disrupted. Roadworks of this nature are therefore unlikely to result in increased TB breakdowns in cattle herds. However, my analyses highlight that there was greater connectivity between social groups than suggested in the literature. I show that badgers made frequent extra-territorial excursions throughout the year. I illustrate that some dispersing badgers travelled long distances through unexpectedly large areas. I describe a previously unrecognised type of ranging behaviour, super-ranging, found in 22% of male badgers. Super-rangers held enlarged territories that encompassed two or more traditional social group territories. All of these behaviours have the potential to increase contact between badgers from different social groups and have implications for disease transmission. My findings can be used to better understand and model the epidemiology of disease, and to formulate more effective and efficient TB control initiatives, such as vaccination of badgers. Finally, this research greatly enhances our understanding of badger ecology, by contributing to knowledge of medium-density populations, and gives a more detailed picture of dispersal in badgers than has been obtained before.