Genetic, social and maternal contributions to Mycobacterium bovis infection status in European badgers (Meles meles).

Within host populations, individuals can vary in their susceptibility to infections and in the severity and progression of disease once infected. Though mediated through differences in behaviour, resistance or tolerance, variation in disease outcomes ultimately stems from genetic and environmental (including social) factors. Despite obvious implications for the evolutionary, ecological and epidemiological dynamics of disease traits, the relative importance of these factors has rarely been quantified in naturally infected wild animal hosts. Here, we use a long-term capture-mark-recapture study of group-living European badgers (Meles meles) to characterize genetic and environmental sources of variation in host infection status by Mycobacterium bovis, the causative agent of bovine tuberculosis (bTB). We find that genetic factors contribute to M. bovis infection status, whether measured over a lifetime or across repeated captures. In the latter case, the heritability (h2 ) of infection status is close to zero in cubs and yearlings but increases in adulthood. Overall, environmental influences arising from a combination of social group membership (defined in time and space) and maternal effects appear to be more important than genetic factors. Thus, while genes do contribute to among-individual variation, they play a comparatively minor role, meaning that rapid evolution of host defences under parasite-mediated selection is unlikely (especially if selection is on young animals where h2 is lowest). Conversely, our results lend further support to the view that social and early-life environments are important drivers of the dynamics of bTB infection in badger populations specifically, and of disease traits in wild hosts more generally.

Living with roommates in a shared den: Spatial and temporal segregation among semifossorial mammals.

Positive interspecific interactions in animal communities (i.e. den sharing) have long been overlooked in animal ecology. The assessment of spatiotemporal overlap among species living within the same burrow system is paramount to explain their strategies of interspecific coexistence. We studied spatiotemporal behavioural patterns of coexistence among four den-sharing mammal species (i.e. the crested porcupine Hystrix cristata, the Eurasian badger Meles meles, the red fox Vulpes vulpes and the European pine marten Martes martes), inhabiting a hilly area of central Italy. Intensive camera trapping (September 2015-September 2018) was used to estimate the interspecific overlap of both temporal and spatial activity patterns for all species combinations. An extensive nocturnal temporal overlap was recorded among all the species, except the diurnal pine marten. However, crested porcupines were mostly active in the darkest nights, whereas bright moonlight enhanced the hunting success of the red fox. Activity of badgers was limited in bright nights only during cold months, when predation pressure and poaching risk were the highest. Crested porcupines avoided spatial sharing outside the den with both nocturnal carnivores, particularly during the winter, when its cubs are in the den. Overlap in ranging areas and activity rhythms between the red fox and the Eurasian badger may be promoted by a remarkable food niche partitioning. Conversely, spatiotemporal overlap between red foxes and pine martens suggested a significant interspecific spatial partitioning, due to the overlap in feeding habits. Den-sharing represents a form of positive interspecific interaction which may limit energy waste and increase local species diversity and densities. Species using the same burrow system may show both spatial and temporal niche partitioning throughout the year, thus allowing a non-competitive coexistence.

What do European badgers (Meles meles) know about the spatial organisation of neighbouring groups?

European badgers (Meles meles) live in groups. Although they can distinguish between a member of their own group, a member of a neighbouring group and a stranger, their ability to understand that neighbouring individuals belong to different groups inhabiting different places, and possibly to build up some representation of the spatial organisation of neighbouring groups remains to be shown. In this study, we conducted a pilot homing experiment to test such ability. Radio-collared badgers were displaced to the home ranges of neighbouring groups and their homing performances were compared to those of badgers displaced either to the periphery of their own group's home range or beyond the neighbouring home ranges. When released in their own home range, badgers homed rapidly and efficiently, whereas when released beyond the neighbouring groups' home ranges (whatever the distance) they did not home. In contrast, badgers released in the home range of a neighbouring group performed some random search there, before returning to their setts quite efficiently. These results suggest that badgers may consider their neighbours as members of different groups inhabiting different places close to their own home range, but their ability to build up some spatial representation of neighbourhood relationships could not be demonstrated.

Perturbing implications of wildlife ecology for disease control.

Britain's Randomised Badger Culling Trial provides robust evidence of the role badgers have in transmission of Mycobacterium bovis to cattle. Culling badgers perturbed their social structure, and brought positive and negative effects for bovine tuberculosis incidence in cattle, leading to the conclusion that culling could not make a meaningful contribution to disease control. The RBCT highlights the complexities of disease transmission in social animals and the importance of host ecology for controlling wildlife diseases.