Effects of culling on badger Meles meles spatial organization: implications for the control of bovine tuberculosis

Abstract

Summary1. The incidence of bovine tuberculosis (TB) in British cattle has risen markedly over the last two decades. Failure to control the disease in cattle has been linked to the persistence of a reservoir of infection in European badgers Meles meles , a nationally protected species. Although badger culling has formed a component of British TB control policy for many years, a recent large-scale randomized field experiment found that TB incidence in cattle was no lower in areas subject to localized badger culling than in nearby areas where no experimental culls occurred. Indeed, analyses indicated that cattle incidence was higher in culled areas. 2. One hypothesis advanced to explain this pattern is that localized culling disrupted badgers' territorial behaviour, potentially increasing the rate of contact between cattle and infected badgers. This study evaluated this hypothesis by investigating badger activity and spatial organization in 13 study areas subjected to different levels of culling. Badger home ranges were mapped by feeding colour-marked baits at badger dens and measuring the geographical area in which colour-marked faeces were retrieved. 3. Badger home ranges were consistently larger in culling areas. Moreover, in areas not subjected to culling, home range sizes increased with proximity to the culling area boundary. Patterns of overlap between home ranges were also influenced by culling. 4. Synthesis and applications. This study demonstrates that culling badgers profoundly alters their spatial organization as well as their population density. These changes have the potential to influence contact rates between cattle and badgers, both where culls occur and on adjoining land. These results may help to explain why localized badger culling appears to have failed to control cattle TB, and should be taken into account in determining what role, if any, badger culling should play in future control strategies.

A long-term observational study of the impact of badger removal on herd restrictions due to bovine TB in the Irish midlands during 1989–2004

“…The role of the badger, has been examined in several large field trials, including the east Offaly project (EOP, during 1989(EOP, during -1995 [2][3][4] ; and the four area project (FAP, 1997(FAP, -2002 [5,6] in Ireland and the Randomized Badger Culling Trial (RBCT, 1998(RBCT, -2006 [7][8][9][10][11][12] in the United Kingdom. In each of these studies, levels of bovine TB in cattle were lower in areas subject to extensive proactive badger culling compared to matched reference areas where culling was either very limited (EOP, FAP) or not undertaken (RBCT).…”

Culling and cattle controls influence tuberculosis risk for badgers

“…These detrimental effects of badger culling were attributed to disruption of badgers' territorial organization and expansion of ranging behavior, which were documented in and around culling areas. This social perturbation potentially increased contact with cattle (5), but is likely to have also influenced contact rates within the badger population (5,6). Whereas epidemiological models usually assume that depressing host population density will reduce disease transmission through lower contact rates, social perturbation could lead badger culling to generate only small reductions, or even increases, in rates of disease transmission, with concomitant effects on infection prevalence (7).…”

Joint Spatio-Temporal Modeling of Mycobacterium bovis Infections in Badgers and Cattle – Results from the Irish Four Area Project

“…In badgers when spatial correlation of disease persisted over both stages the direction of clustering changed. Even when spatial correlation of disease was not present in both stages, the geometry of where badger setts were located did change Tuyttens et al 2000;Woodroffe et al 2006). The changing geometry may also be due in part to edge effects, caused by immigration of badgers back into an area, as stated in Section 2.…”