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While there is irrefutable evidence for the transfer of bovine TB between badgers and cattle, the mechanisms of transfer are not clearly documented. In order to reduce such transfer, it is obviously important to understand how infection takes place.
With such questions in mind, data from a study of free-ranging badgers was combined with detailed records of paddock use by cattle. Each study badger was carrying a personal GPS unit on a tailored collar, so their movements could be monitored to within a few meters. The paddock use of the cattle was recorded on a daily basis. The data were combined, using mapping software, such that a daily log could be constructed for badger and cattle activity.
The level of badger activity was determined for each paddock, in the presence and absence of grazing cattle. Badgers were found to avoid paddocks containing cattle. In addition, although the badgers showed preferences for some paddocks over others, even the preferred paddocks were usually avoided when cattle were present.
These findings do not correspond with British studies (Boehm et al. 2009), which showed British badgers and cattle meet frequently in pastures. It is unclear why British and Irish badgers appear to show these behavioural differences. It may, potentially, relate to differences in the grazing systems studied, the density of badger populations in Britain and Ireland or individual badger behaviour patterns.
This study demonstrates that free-ranging Irish badgers avoid entering paddocks when there are cattle present. Therefore it seems unlikely that direct contact between grazing cattle and healthy badgers under a paddock grazing system is a major route of bovine TB transmission in Ireland. Future strategies for controlling cross-infection between badgers and cattle may need to focus on the behaviour of badgers with advanced generalised TB, indirect contact between badgers and cattle or contact between badgers and cattle in farmyards or farm buildings.
Further Reading
Oral badger vaccine field trial under way in Ireland
Author
David J Kelly: djkelly[at]tcd.ie
Photo credit
Jason Venus