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

Aoibheann Gaughran,Margaret Good,Enda Mullen,Nicola M Marples,Teresa Macwhite,David J Kelly,Peter Maher

doi:10.1002/ece3.5753

Abstract

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.

Highlights

Knowledge of ranging behavior and animal movement is important where infectious diseases are difficult to control (Conner & Miller, 2004)
Badger movements into and out of neighboring social groups are associated with increased preva‐ lence of TB in these groups (Riordan, Delahay, Cheeseman, Johnson, & Macdonald, 2011; Rogers et al, 1998)
The movement of badgers is of direct importance to the transmission of TB infec‐ tion both between individual badgers (O'Mahony, 2015; Weber et al, 2013) and between badgers and cattle (Eves, 1999; Griffin et al, 2005; Martin et al, 1997; Mullen et al, 2015; Woodroffe et al, 2009)

Summary

Introduction

Knowledge of ranging behavior and animal movement is important where infectious diseases are difficult to control (Conner & Miller, 2004). European badgers (Meles meles, Figure 1) are highly susceptible to Mycobacterium bovis, the causative agent of tubercu‐ losis (TB) (Gormley & Costello, 2003). In both Ireland and the UK, badgers have been implicated in the spread of M. bovis to cattle and in acting as a wildlife reservoir for bovine TB (Corner, Murphy, & Gormley, 2011; Godfray et al, 2013; Murphy, Gormley, Costello, O'Meara, & Corner, 2010). The organization of badgers into territo‐ rial social groups arguably limits the spread of TB because it lowers disease transmission rates between groups The movement of badgers is of direct importance to the transmission of TB infec‐ tion both between individual badgers (O'Mahony, 2015; Weber et al, 2013) and between badgers and cattle (Eves, 1999; Griffin et al, 2005; Martin et al, 1997; Mullen et al, 2015; Woodroffe et al, 2009)

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