L. Forró szerk.: Miscellanea Zoologica Hungarica 12. 1998 (Budapest, 1998)
Horváth, Gy.: Population dynamics and trappability of four rodent species in a forest habitat
cold March, rodent populations suffered a serious drop in numbers by spring 1996. The MNA values demonstrate well that in the period before August much fewer individuals were captured than in the previous year, and even the September maxima were lower. A. agrárius was the most frequently trapped species in autumn 1996, but with a much lower maximum than in 1995. For this 15-month period significant rank correlation values were obtained in the case of four species-pairs. Changes in numbers were less similar in A. flavicollis vs. A. sylvaticus (R s = 0.55, p < 0.05). The abundance trend of C. glareolus was similar to that of A. agrárius (R s = 0.63, p < 0.02), and identical significance level was shown for the positive correlations between abundances of the pairs C. glareolus vs. A. flavicollis and A. agrárius vs. A. flavicollis, respectively (for both: R s = 0.67-0.71, p < 0.01). In 1997 two abundance maxima could be observed in both A. flavicollis and C. glareolus, which do not coincide in the two species (Fig. 2). A. flavicollis reached its demographic maximum in May-June and September, while C. glareolus was the most abundant in July and October. A. agrárius was caught in high numbers in February-March, but by the end of spring its numbers had declined, to increase again only in the autumn to the extent that this species had the highest MNA in September. Throughout the year A. sylvaticus was trapped in very low numbers. As revealed by Spearman rank-correlation, population demographic trends of A. flavicollis and A. sylvaticus were the most similar to each other during this year (R s =0.85, p < 0.01). At a lower significance level, the population changes of A. agrárius ran nearly synchronously with those of A. flavicollis (R s =0.64, p < 0.05). As opposed to the 15month period, no significant rank-correlation values were obtained for the A. agrárius vs. C. glareolus and the A. flavicollis vs. C. glareolus species-pairs, which can also be seen on the MNA curves. In cases of higher numbers of C. glareolus in the area, the other two species were represented at a low abundance level. The trend of changes in population sizes estimated for the 1995-1996 period using the D model of the JOLLY programme is similar to the MNA trend, with actual values of the estimation being higher (Fig. 3). The sudden autumn population growth of A. agrárius can be clearly seen, which collapses by next spring. However, spring and summer in 1996 did not lead
