B. Cooke comments that similarities between patterns in the lynx data and the "spatiotemporal patterns" produced by the simulation model used by Ranta et al. "appear to be superficial and exaggerated by their analytical methods." He states that "a cross-correlation coefficient is a meaningful measure of synchrony only when the population data are stationary" and that it "seems an inaccurate measure of synchrony for populations that cycle in phase and then suddenly snap out of phase."

In response, Ranta et al. agree that "nonstationarity is certainly an aspect to be taken into account" and state that the lynx data and the simulation results are stationary. Their reanalysis of the data "so that this linear trend [nonstationarity in the 15-year sliding-window analysis] is removed ... shows that synchrony of fluctuation over time remains, although some details change." Also, "the use of a time window larger than 15 years, or moving the window in increments larger than 1 year, does not change [their] conclusions."

The full text of these comments can be seen at www.sciencemag.org/cgi/content/full/281/5382/1415a