Response of an arctic predator guild to collapsing lemming cycles

Abstract

Alpine and arctic lemming populations appear to be highly sensitive to climate change, and when faced with warmer and shorter winters, their well-known high-amplitude population cycles may collapse. Being keystone species in tundra ecosystems, changed lemming dynamics may convey significant knock-on effects on trophically linked species. Here, we analyse long-term (1988-2010), community-wide monitoring data from two sites in high-arctic Greenland and document how a collapse in collared lemming cyclicity affects the population dynamics of the predator guild. Dramatic changes were observed in two highly specialized lemming predators: snowy owl and stoat. Following the lemming cycle collapse, snowy owl fledgling production declined by 98 per cent, and there was indication of a severe population decline of stoats at one site. The less specialized long-tailed skua and the generalist arctic fox were more loosely coupled to the lemming dynamics. Still, the lemming collapse had noticeable effects on their reproductive performance. Predator responses differed somewhat between sites in all species and could arise from site-specific differences in lemming dynamics, intra-guild interactions or subsidies from other resources. Nevertheless, population extinctions and community restructuring of this arctic endemic predator guild are likely if the lemming dynamics are maintained at the current non-cyclic, low-density state.

Figure 1.

Predator–prey dynamics in northeast Greenland during the period 1988–2010: (a) collared lemmings, (b) stoat-depredated lemming nests, (c) snowy owl nests, (d) long-tailed skua nests and (e) the fraction of arctic fox dens used for breeding. Upper panels show numbers per hectare or fractions during the study period, whereas the lower panels show the continuous wavelet transform of the log- or arcsine-transformed time series. Heat colours denote the power of the spectra, and bold contour lines enclosing the red coloured spectrum denote significant periodicity. The cone marks the area of influence.

Figure 2.

Generalized additive model (GAM) plots of predator reproductive response to high-arctic collared lemming densities on Traill Island (1988–2010) and Zackenberg (1996–2010). Densities are numbers per hectare. Blue colours indicate data from Traill Island, whereas red colours indicate data from Zackenberg. Shaded areas are the 95% confidence limits for the site-specific GAMs with 2 degrees of freedom. The F-statistics and p-values for the specific GAMs are given in each plot, while D shows the deviance explained.