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Synchronization of animal population dynamics by large-scale climate


The hypothesis that animal population dynamics may be synchronized by climate1 is highly relevant in the context of climate change because it suggests that several populations might respond simultaneously to climatic trends if their dynamics are entrained by environmental correlation. The dynamics of many species throughout the Northern Hemisphere are influenced by a single large-scale climate system, the North Atlantic Oscillation (NAO)2,3, which exerts highly correlated regional effects on local weather4. But efforts to attribute synchronous fluctuations of contiguous populations to large-scale climate are confounded by the synchronizing influences of dispersal or trophic interactions5. Here we report that the dynamics of caribou and musk oxen on opposite coasts of Greenland show spatial synchrony among populations of both species that correlates with the NAO index. Our analysis shows that the NAO has an influence in the high degree of cross-species synchrony between pairs of caribou and musk oxen populations separated by a minimum of 1,000 km of inland ice. The vast distances, and complete physical and ecological separation of these species, rule out spatial coupling by dispersal or interaction. These results indicate that animal populations of different species may respond synchronously to global climate change over large regions.

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We thank O. Bjørnstad and W. Koenig for analytical advice; and T. Coulson and E. Ranta for comments. E.P. acknowledges the financial support of the National Science Foundation and the Environmental Consortium at Pennsylvania State University. M.C.F. acknowledges the financial support of the Danish National Science Research Council.

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Correspondence to Eric Post.

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Figure 1: Correlations between the NAO and local weather and population synchrony in Greenland.
Figure 2: Distance-dependent population synchrony and weather correlations.
Figure 3: Relation between the degree of pairwise cross-correlation between caribou and musk oxen populations and the ratio of the effect of the NAO on the dynamics of each population (r = 0.65, P < 0.001).


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