Parasitic Worms and Population Cycles of Red Grouse

Many years before Charles Elton collected the detailed data on fur returns to The Hudson’s Bay Trading Company, or described the regular fluctuations in small mammal numbers, scientists and naturalists had observed and were proposing explanations for the cause of periodic crashes in numbers of red grouse known as “grouse disease.” MacDonald (1883) claimed “that it was more than eighty years since the alarm of grouse disease was sounded in this country,” implying that naturalists were starting to examine the phenomenon nearly 200 years ago. In 1873, The House of Commons established a Select Committee to consider the game laws of the United Kingdom and, since this had followed a year of particularly severe population collapse in red grouse numbers, they took exhaustive evidence on a wide range of possible causes of “grouse disease.” An examination of the letters in The Times and The Field shows that the debate over the cause of the population crashes was contentious and as heated as many of the recent debates over the causes of population cycles. Scientific studies were initiated by Cobbold (1873) who examined grouse killed during a population crash, published a pamphlet that described the presence of large numbers of “strongle worms,” and advocated the theory that the cause of grouse disease was wholly due to the presence of nematode worms. In 1905, the Board of Agriculture appointed a Committee of Inquiry on Grouse Disease to investigate the life history of the parasite and the causes of “grouse disease.” The extensive survey and detailed analysis was quite remarkable for the time, and was presented in a two-volume publication (Lovat 1911). The Committee surveyed grouse populations, undertook experiments and, after nearly 2000 dissections, came to the conclusion that “the strongyle worm, and the strongyle worm alone, is the immediate causa causans of adult ‘Grouse Disease.’“ The Principal Field Officer was E. A. Wilson, a gifted artist and scientist who was later appointed as the Scientific Director to Captain Scott’s Antarctic expedition on the Terra Nova. Unfortunately, Wilson never saw the production of the final report as he died with Scott during their return from the South Pole.