Population regulation in snowshoe hare and lynx populations: asymmetric food web configurations between the snowshoe hare and the lynx

Proceedings of the National Academy of Science USA (1997) 94:5147-5152.
Communicated by Sir Robert May, Oxford, UK.

Abstract

The snowshoe hare and the Canadian lynx in the boreal forests of North America show 9-11 yrs density cycles. These are generally assumed to be linked to each other because lynx are specialist predators on hares. Based on time series data for hare and lynx, we show that the dominant dimensional structure of the hare series appears to be three while that of the lynx is two. The 3-dimensional structure of the hare time series is hypothesized due to a 3-trophic level model in which the hare may be seen as simultaneously regulated from below and above. The plant species in the hare diet appear compensatory to one another, and the predator species may, likewise, be seen as an internally compensatory guild. The lynx time series are, in contrast, consistent with a model of donor-control in which their populations are regulated from below by prey availability. Altogether our analysis suggest that the classic view of a symmetric hare-lynx interaction is too simplistic. Specifically, we argue that the classic food chain structure is inappropriate: the hare is influenced by many predators other than the lynx, while the lynx is primarily influenced by the snowshoe hare.

Key words: statistical modeling, generalized additive models, population dynamics, dimension