Badger (Meles meles) contact metrics in a medium-density population

Badger territoriality maintained despite disturbance of major road construction

Road ecology has traditionally focused on the impact of in-situ and functional roads on wildlife. However, road construction also poses a major, yet understudied, threat and the implications for key aspects of animal behaviour are unknown. Badgers (Meles meles) have been implicated in the transmission of tuberculosis to cattle. There are concerns that environmental disturbances, including major road construction, can disrupt badger territoriality, promoting the spread of the disease to cattle. To address these knowledge gaps the ranging behaviour of a medium-density Irish badger population was monitored using GPS-tracking collars before, during, and after a major road realignment project that bisected the study area. We estimated badgers’ home range sizes, nightly distances travelled, and the distance and frequency of extra-territorial excursions during each phase of the study and quantified any changes to these parameters. We show that road construction had a very limited effect on ranging behaviour. A small increase in nightly distance during road construction did not translate into an increase in home range size, nor an increase in the distance or frequency of extra-territorial excursions during road construction. In addition, suitable mitigation measures to prevent badger deaths appeared to ensure that normal patterns of ranging behaviour continued once the new road was in place. We recommend that continuous badger-proof fencing be placed along the entire length of new major roads, in combination with appropriately sited underpasses. Our analysis supports the view that road construction did not cause badgers to change their ranging behaviour in ways likely to increase the spread of tuberculosis.

Does Mycobacterium tuberculosis var. bovis Survival in the Environment Confound Bovine Tuberculosis Control and Eradication? A Literature Review

Bovine tuberculosis (bTB) is one of the globe's most common, multihost zoonoses and results in substantial socioeconomic costs for governments, farming industries, and tax payers. Despite decades of surveillance and research, surprisingly, little is known about the exact mechanisms of transmission. In particular, as a facultative intracellular pathogen, to what extent does survival of the causative agent, Mycobacterium tuberculosis var. bovis (M. bovis), in the environment constitute an epidemiological risk for livestock and wildlife? Due largely to the classical pathology of cattle cases, the received wisdom was that bTB was spread by direct inhalation and exchange of bioaerosols containing droplets laden with bacteria. Other members of the Mycobacterium tuberculosis complex (MTBC) exhibit differing host ranges, an apparent capacity to persist in environmental fomites, and they favour a range of different transmission routes. It is possible, therefore, that infection from environmental sources of M. bovis could be a disease transmission risk. Recent evidence from GPS-collared cattle and badgers in Britain and Ireland suggests that direct transmission by infectious droplets or aerosols may not be the main mechanism for interspecies transmission, raising the possibility of indirect transmission involving a contaminated, shared environment. The possibility that classical pulmonary TB can be simulated and recapitulated in laboratory animal models by ingestion of contaminated feed is a further intriguing indication of potential environmental risk. Livestock and wildlife are known to shed M. bovis onto pasture, soil, feedstuffs, water, and other fomites; field and laboratory studies have indicated that persistence is possible, but variable, under differing environmental conditions. Given the potential infection risk, it is timely to review the available evidence, experimental approaches, and methodologies that could be deployed to address this potential blind spot and control point. Although we focus on evidence from Western Europe, the concepts are widely applicable to other multihost bTB episystems.

Extra Territorial Excursions by European badgers are not limited by age, sex or season

European badgers (Meles meles) in medium and high density populations show strong territorial behaviour. Territories in these populations are contiguous, well-marked and often unchanging over many years. However, badgers do not always stay within their territorial boundaries. In our medium-density population, most individual badgers made extra-territorial excursions (ETEs) throughout the year. ETEs were most frequent between April and September and least frequent in December and January (the period of winter lethargy). Male badgers made longer and more frequent ETEs than females (especially between January and March, and in autumn). Breeding females made longer and more frequent ETEs than non-breeding females in November. While these peaks correspond with the main mating seasons, mating activity does not explain ETEs throughout the year. The shorter, but more frequent, ETEs in summer months may serve a monitoring purpose, rather than simply providing additional mating opportunities with badgers from outside the 'home' social group. We found that young badgers did not make regular ETEs until the summer of their second year. If badgers could be vaccinated as cubs, this would reduce any potential risk of TB spread during ETEs.

Individual and seasonal variation in contact rate, connectivity and centrality in red fox (Vulpes vulpes) social groups

Examining temporal variation in social connectivity and relating this to individual behaviour can help understand the role of individuals within social groups. Although red foxes are solitary foragers, they form social groups at higher population densities. To investigate the effects of season, sex and status on social connectivity in red fox social groups, we set camera traps for four consecutive seasons to record contact rates and social network metrics at food patches in seven fox territories. Higher food availability was associated with higher contact rates. Individual contact rates peaked in different seasons depending on sex and social status. Dominant foxes held central network positions in all seasons but there was no consistent pattern in social connections within territories, suggesting a greater influence of features such as group size and composition on network structure than seasonal behaviour. Increased extraterritorial movements by males during winter contributed to a significant reduction in local network connectivity. Female network strength did not vary with season, suggesting that females play an important role in maintaining year-round group cohesion. These data advance our understanding of canid social systems, the benefits of group-living in solitary foraging carnivores, and the impacts of management interventions for an ecologically important species.

Dispersal patterns in a medium-density Irish badger population: Implications for understanding the dynamics of tuberculosis transmission

European badgers (Meles meles) are group-living mustelids implicated in the spread of bovine tuberculosis (TB) to cattle and act as a wildlife reservoir for the disease. In badgers, only a minority of individuals disperse from their natal social group. However, dispersal may be extremely important for the spread of TB, as dispersers could act as hubs for disease transmission. We monitored a population of 139 wild badgers over 7 years in a medium-density population (1.8 individuals/km2). GPS tracking collars were applied to 80 different individuals. Of these, we identified 25 dispersers, 14 of which were wearing collars as they dispersed. This allowed us to record the process of dispersal in much greater detail than ever before. We show that dispersal is an extremely complex process, and measurements of straight-line distance between old and new social groups can severely underestimate how far dispersers travel. Assumptions of straight-line travel can also underestimate direct and indirect interactions and the potential for disease transmission. For example, one female disperser which eventually settled 1.5 km from her natal territory traveled 308 km and passed through 22 different territories during dispersal. Knowledge of badgers' ranging behavior during dispersal is crucial to understanding the dynamics of TB transmission, and for designing appropriate interventions, such as vaccination.

Bovine Tuberculosis in Britain and Ireland - A Perfect Storm? the Confluence of Potential Ecological and Epidemiological Impediments to Controlling a Chronic Infectious Disease

Successful eradication schemes for bovine tuberculosis (bTB) have been implemented in a number of European and other countries over the last 50 years. However, the islands of Britain and Ireland remain a significant aberration to this trend, with the recent exception of Scotland. Why have eradication schemes failed within these countries, while apparently similar programs have been successful elsewhere? While significant socio-economic and political factors have been discussed elsewhere as key determinants of disease eradication, here we review some of the potential ecological and epidemiological constraints that are present in these islands relative to other parts of Europe. We argue that the convergence of these potential factors may interact additively to diminish the potential of the present control programs to achieve eradication. Issues identified include heterogeneity of diagnostic testing approaches, the presence of an abundant wildlife reservoir of infection and the challenge of sustainably managing this risk effectively; the nature, size, density and network structure of cattle farming; potential effects of Mycobacterium bovis strain heterogeneity on disease transmission dynamics; possible impacts of concurrent endemic infections on the disclosure of truly infected animals; climatological differences and change coupled with environmental contamination. We further argue that control and eradication of this complex disease may benefit from an ecosystem level approach to management. We hope that this perspective can stimulate a new conversation about the many factors potentially impacting bTB eradication schemes in Britain and Ireland and possibly stimulate new research in the areas identified.

Super-ranging. A new ranging strategy in European badgers

We monitored the ranging of a wild European badger (Meles meles) population over 7 years using GPS tracking collars. Badger range sizes varied seasonally and reached their maximum in June, July and August. We analysed the summer ranging behaviour, using 83 home range estimates from 48 individuals over 6974 collar-nights. We found that while most adult badgers (males and females) remained within their own traditional social group boundaries, several male badgers (on average 22%) regularly ranged beyond these traditional boundaries. These adult males frequently ranged throughout two (or more) social group’s traditional territories and had extremely large home ranges. We therefore refer to them as super-rangers. While ranging across traditional boundaries has been recorded over short periods of time for extraterritorial mating and foraging forays, or for pre-dispersal exploration, the animals in this study maintained their super-ranges from 2 to 36 months. This study represents the first time such long-term extra-territorial ranging has been described for European badgers. Holding a super-range may confer an advantage in access to breeding females, but could also affect local interaction networks. In Ireland & the UK, badgers act as a wildlife reservoir for bovine tuberculosis (TB). Super-ranging may facilitate the spread of disease by increasing both direct interactions between conspecifics, particularly across social groups, and indirect interactions with cattle in their shared environment. Understanding super-ranging behaviour may both improve our understanding of tuberculosis epidemiology and inform future control strategies.

Seasonal variation in daily patterns of social contacts in the European badger Meles meles

Social interactions among hosts influence the persistence and spread of infectious pathogens. Daily and seasonal variation in the frequency and type of social interactions will play an important role in disease epidemiology and, alongside other factors, may have an influence on wider disease dynamics by causing seasonal forcing of infection, especially if the seasonal variation experienced by a population is considerable. We explored temporal variation in within-group contacts in a high-density population of European badgers Meles meles naturally infected with Mycobacterium bovis (the causative agent of bovine tuberculosis). Summer contacts were more likely and of longer duration during the daytime, while the frequency and duration of winter contacts did not differ between day and night. In spring and autumn, within-group contacts peaked at dawn and dusk, corresponding with when they were of shortest duration with reduced potential for aerosol transmission of pathogens. Summer and winter could be critical for transmission of M. bovis in badgers, due to the high frequency and duration of contacts during resting periods, and we discuss the links between this result and empirical disease data. This study reveals clear seasonality in daily patterns of contact frequency and duration in species living in stable social groups, suggesting that changes in social contacts could drive seasonal forcing of infection in wildlife populations even when the number of individuals interacting remains similar.

Assessment of listing and categorisation of animal diseases within the framework of the Animal Health Law (Regulation (EU) No 2016/429): bovine tuberculosis

Bovine tuberculosis has been assessed according to the criteria of the Animal Health Law (AHL), in particular criteria of Article 7 on disease profile and impacts, Article 5 on the eligibility of bovine tuberculosis to be listed, Article 9 for the categorisation of bovine tuberculosis according to disease prevention and control rules as in Annex IV and Article 8 on the list of animal species related to bovine tuberculosis. The assessment has been performed following a methodology composed of information collection and compilation, expert judgement on each criterion at individual and, if no consensus was reached before, also at collective level. The output is composed of the categorical answer, and for the questions where no consensus was reached, the different supporting views are reported. Details on the methodology used for this assessment are explained in a separate opinion. According to the assessment performed, bovine tuberculosis can be considered eligible to be listed for Union intervention as laid down in Article 5(3) of the AHL. The disease would comply with the criteria as in Sections 2, 3, 4 and 5 of Annex IV of the AHL, for the application of the disease prevention and control rules referred to in points (b), (c), (d) and (e) of Article 9(1). The main animal species to be listed for bovine tuberculosis according to Article 8(3) criteria are several mammal species, as indicated in the present opinion.