The effects of parasitic infections on the population fluctuations of red grouse in the North of England.
1. The object of this study was to elucidate the role of parasitism in the population fluctuations of red grouse in the north of England.
2. Analysis of bag records from 52 estates demonstrated that 82% of grouse moors produce bag records that fluctuate in a regular manner.
3. The breeding success of female red grouse treated with an anthelmintic, to reduce an infection of the nematode Trichostrongylus tenuis, was significantly greater than a control group in two years.
4. The construction of a simulation model demonstrated that the evident effects of parasitism on breeding success could be an important mechanism generating the population cycles in red grouse.