Testing the role of parasites in driving the cyclic population dynamics of a gamebird

• Published in: Ecology letters Vol. 9; no. 4; pp. 410 - 418
• Main Authors: Redpath, Stephen M, Mougeot, François, Leckie, Fiona M, Elston, David A, Hudson, Peter J
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01.04.2006; Blackwell Publishing Ltd
• Subjects: Animals; autumn; breeding; Experiment; Female; Food Chain; Galliformes - growth & development; Galliformes - parasitology; game birds; grouse; Host-Parasite Interactions; Lagopus lagopus scoticus; Male; parasites; parasitism; Population Density; Population Dynamics; population regulation; red grouse; Reproduction; Seasons; spring; Trichostrongylus tenuis; unstable dynamics
• ISSN: 1461-023X; 1461-0248; 1461-0248
• DOI: 10.1111/j.1461-0248.2006.00895.x

The role of parasites in regulating populations has been the subject of debate. We tested whether parasites caused population cycles in red grouse by manipulating parasite intensities in four, paired 1 km² study areas during cyclic population declines over 4 years. Parasite reductions led to (1) larger grouse broods, (2) higher population densities in both autumn and spring, (3) reduced autumn population declines in one of two regions, and (4) reduced spring declines, but only in the first year. We infer that a single trophic interaction between a parasite and its host does not explain cyclic dynamics in spring breeding density in this species, although it contributed to the start of a cyclic decline. Another process was operating to drive the populations down. Together with our other results these findings emphasize that both trophic and intrinsic processes may act within populations to cause unstable dynamics.