With grouse moors offering a sound capital investment and in the UK, the only country in the world to offer the practice of driven grouse shooting, it is becoming increasingly important to track the grouse and the impact of medicated grit. Fenbendazole, the wormer used in the grit, if correctly applied, will help keep parasite burdens down and maintain the health and thereby the population of Red Grouse. Correct and good management of red grouse will increase the chances of breeding waders and black grouse being present so this question on the impact of medicated grit is an important issue.
The GWCT (Game and Wildlife Conservation Trust) have flagged up that red grouse are possibly becoming resistant to Fenbendazole, with indications of an increase in the Strongyle worm which causes poor breeding success and periodic population crashes in the grouse. Managing the worm burden rather than trying to eradicate the problem must be the way forward, supplying the medicated grit timely, otherwise the treatment may be back firing as the resistance becomes established. It is hard to track and control exactly how much grouse visit the grit piles and also how much each will take on board together with others developing resistancy. Treatment success does vary hugely and the dose rate varies from bird to bird and from moor to moor.
The past few years, however, have shown that treating with medicated grit indicates the grouse population densifying with good winter survival rates and it is certainly having a positive impact. It is only recently that there is the concern of the developing resistance so advice to manage and feed intermittently rather than an attempt to eradicate and feed all the time is in place.
Indications from the Langholm Moor Demonstration Project suggest the levels of the nematode worm Trichostronglyus tenuis are below the thresholds considered to be a problem for grouse. With dedicated routine sampling of worm eggs in grouse to take place each year and the additional awareness of possible resistance to the medication, the grouse population looks to be steady. The GWTC recent report suggests that direct dosing the grouse could be considered and be most effective when high worm infection is expected (usually spring) with impact of medicated grit being positive in keeping worm burdens at a low level.
Excellent support from the Grouse Technical Services group within GWTC is available and they offer basic disease and population monitoring services, will do worm counts, advise on medication and improving grouse health. The Red Grouse population is being carefully managed and controlled.