Insights into population ecology of red grouse from long-term studies

Abstract

Long-term studies have been the backbone of population ecology. The red grouse (Lagopus lagopus scoticus) is one species that has contributed widely to this field since the 1950s. Here we summarise how different mechanisms have been identified, tested and accepted or rejected at explaining population dynamics in red grouse. Red grouse research has combined long-term studies of marked individuals -with demographic studies over wide geographical areas and replicated individual- and population-level manipulations. A main focus has been on understanding the causes of population cycles in red grouse, and in particular the relative importance of intrinsic (behaviour) and extrinsic (climate, food limitation and parasite) mechanisms. Separate studies conducted in different regions initially proposed either the nematode parasite Trichostrongylus tenuis or changes in male aggressiveness in autumn as drivers of population cycles. More recent experiments suggest that parasites are not a necessary cause for cycles and have highlighted that behavioural and parasite-mediated mechanisms are interrelated. Red grouse studies have had an important impact on the field of population ecology, in particular through highlighting: (1) the impact of parasites on populations; (2) the role of intrinsic mechanisms in cyclic dynamics, and (3) the need to consider multiple, interacting mechanisms. As take-home message, we wanted to highlight the need to keep on conducting long-term and individually-based research to advance in our understanding not just of population dynamics, but also in other fields like micro-evolution, phenotypic plasticity or population genetics.