L. Forró szerk.: Miscellanea Zoologica Hungarica 12. 1998 (Budapest, 1998)

Horváth, Gy.: Population dynamics and trappability of four rodent species in a forest habitat

Fig. 3. Population size estimates of four rodent species in 1995-1996, as estimated by the D-model of the JOLLY computer programme (with 95 % confidence interval values shown as bars) to the demographic decline of this species only: the other three species were also found in very small numbers in the area until August 1996. The rise in population density was late that year, starting only as late as in August, which meant a three-month delay in comparison with the preceding years. This temporal shift of changes in population sizes is well represented by the estimation output values of the D model. The accuracy of the estimation was tested by calculating the coefficient of variation of population sizes (Table 1). Values were not within the limits of acceptability in the case of A. sylvaticus, with figures ranging well above 20%. Table 1. Coefficient of variation (cv[%]) of population size estimates of four rodent species in 1995-1996, based on the D-model 1995-1996/Months A. flavicollis A. sylvaticus A. agrárius C. glareolus July 20.84 49.47 14.02 19.72 August 15.04 35.47 9.23 17.41 September 13.60 34.77 7.01 18.03 October 15.92 34.16 6.39 21.08 February 25.93 30.08 19.74 29.09 March 29.97 42.38 25 29.16 April 43.90 42.57 25 50.74 May 42.52 42.24 35.08 June 32.70 47.41 July 17.90 61.01 45.6 26.66 August 17.25 41.92 20.96 27.56 September 13.49 38.63 10.37 22.04 October 11.98 41.49 7.67 24.05 November 13.46 43.03 7.78 20.02