SUPPORTING ONLINE MATERIAL Cyclic dynamics in a simple vertebrate predator-prey community

• Main Authors: Olivier Gilg, Ilkka Hanski, Benoît Sittler
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Arctic; Arctic Fox; Arctic hare; Long-tailed Skua; muskox; snowy owl
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.407.2547; http://www.helsinki.fi/~ihanski/Articles_by_others/Science_Gilg_SOM_1087509s_new.pdf

In our model (main article), the numbers of lemmings predated by the arctic fox, the long-tailed skua and the snowy owl were calculated based on the functional and numerical responses of the predators presented in Fig. 1 (main article). All these species feed mostly on lemmings, which account for>90 % of their diet when lemming densities are>1 ind./ha. At lower lemming densities, the main alternate prey are birds (ptarmigan, waders and passerines) for the snowy owl, small birds, fishes, invertebrates and berries for the long-tailed skua, and arctic hare, muskox carrion, birds, eggs, invertebrates and berries for the arctic fox (O. Gilg et al. in prep.). Below, we present a more detailed description of the methods used to calculate (i) the functional and (ii) numerical responses of these predators to the lemming density, (iii) the fieldestimated parameter values (Table S1), and (iv) how we implemented the numerical responses in the model (the functional responses were simply added to the prey equation as presented in the main article). Additionally, we describe (v) how we estimated the lemming density at snowmelt (N’) based on the density of winter nests for 1988-2002 and on direct live-trapping for 1998-2002. We present (vi) the empirical support for lack of space or food limitation in lemming dynamics. We