Mountain hares, louping-ill, red grouse and harvesting: complex interactions but few data

Abstract

First paragraph: Our recent paper examined the impact of a large-scale field manipulation of mountain hare density on the dynamics of ticks, louping-ill and red grouse (Laurenson et al. 2003). We found that hares were an important host for ticks and for the transmission of louping-ill, and that tick burdens and louping-ill seroprevalence in grouse declined when hare densities were reduced, in comparison to a control. In addition, the number of young grouse produced per adult bird increased, but no effect on grouse density was found. Our model of the system showed that the dynamical decline in louping-ill can be accounted for through the decline of both ticks and the process of non-viraemic transmission. Cope, Iason & Gordon (2004) make two broad sets of observations on this study. First, they comment on the limitations of the controls. Secondly, they make minor modifications to an existing model of nematode-driven grouse cycles, replicating previously published research (Hudson et al.2002) and use it to confirm the same finding that louping-ill virus may be expected to dampen grouse cycles. Combined, the authors use these observations to argue that a policy of reducing mountain hare density to keep grouse moors economically viable has not been proven and go on to imply that louping-ill may even improve the economics of grouse harvesting.