Interactions between intrinsic and extrinsic mechanisms in a cyclic species: Testosterone increases parasite infection in red grouse

Linzi J. Seivwright, Stephen M. Redpath, François Mougeot, Fiona Leckie, Peter J. Hudson

Research output: Contribution to journalArticle

46 Scopus citations

Abstract

Field studies of mechanisms involved in population regulation have tended to focus on the roles of either intrinsic or extrinsic factors, but these are rarely mutually exclusive and their interactions can be crucial in determining dynamics. Experiments on red grouse Lagopus lagopus scoticus have shown that population instability can be caused both by the effects of a parasitic nematode, Trichostrongylus tenuis, on host production or by changes in testosterone influencing aggressive behaviour and recruitment. We experimentally tested for an interaction between testosterone and T. tenuis in free-living male grouse. A total of 123 grouse were caught in autumn, treated with an anthelmintic to remove parasites, and then given either testosterone or empty, control, implants. After one month grouse were re-infected with a standard dose of parasites. We show that males with increased testosterone levels had greater parasite intensities than controls after one year. We discuss possible physiological and behavioural mechanisms linking testosterone and increased parasite intensity, and the implications for our understanding of complex, unstable population dynamics.

Original languageEnglish (US)
Pages (from-to)2299-2304
Number of pages6
JournalProceedings of the Royal Society B: Biological Sciences
Volume272
Issue number1578
DOIs
StatePublished - Nov 7 2005

All Science Journal Classification (ASJC) codes

  • Biochemistry, Genetics and Molecular Biology(all)
  • Immunology and Microbiology(all)
  • Environmental Science(all)
  • Agricultural and Biological Sciences(all)

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