Table 2.

Cross-correlation coefficients with time lags of −1, 0 and 1 years calculated between Microtus voles (main prey of predators), and bank voles, water voles, pooled harvest and house mice, and common shrews.

(Coefficients in columns labelled ‘data’ are calculated from ln-transformed trapping index series of the respective species. Coefficients in columns labelled ‘residuals’ are calculated from residuals of autoregressive models fitted to the ln-transformed trapping series (AR(2) for Microtus voles, bank voles and common shrews, AR(1) for water voles and mice; see figure 2). Bold values indicate significant correlations according to Bartlett’s test. For the ‘data’ coefficients, significant positive values at time lag (0) indicate synchronously fluctuating populations. For the ‘residuals’ coefficients, significant positive values at time lag (0) indicate synchrony in population fluctuations independent of autocorrelation structure.)

		Microtus voles with time lag (year)
		−1		0		1
alternative prey species	n	data	residuals	data	residuals	data	residuals
bank vole	27	−0.44	−0.34	0.79	0.42	−0.28	−0.21
water vole	23	−0.31	−0.13	0.19	0.05	−0.05	−0.16
mice	27	−0.52	−0.33	0.13	−0.09	0.29	0.10
common shrewa	27	−0.51	−0.12	0.37b	0.22	0.11	0.15

^a Original trapping data detrended by fitting a second-order polynomial curve.

^b The cross-correlation coefficient fell 0.01 units short of statistical significance.