| Abstract [eng] |
THE SPECIFIC STRUCTURE AND MIGRATION OF SMALL MAMMALS IN THE FLOODED MEADOWS OF THE NEMUNAS DELTA Agnė Janonytė The Nemunas Delta Regional Park (W. Lithuania) is characterized by exceptional habitat diversity. Flooded meadows on Rusnė Island border with non-flooded meadows and are separated by channels and dikes. Birds are well known in the area, as the site is enlisted as a habitat of the European importance and Ramsar site, but small mammals were scarcely investigated to date. Small mammals were trapped from June 2004 to October 2006. The total catch in both flooded and non-flooded meadows was 621 specimens. They belong to 10 species. The absolute dominant was root vole (M. oeconomus), with the share of 55% in the whole area. For the first time in Lithuania, the data on breeding of M. oeconomus were collected (32 cases). We found litter size differences according to the season and habitat. Totally, litter size of M. oeconomus in flooded meadows was 5.87±1.10 (2–11), while that in non-flooded meadows – 6.20±0.38 (3–10) embryo. In May, litter size was higher in flooded meadows – 10.0±1.0 vs. 7.75±0.63 embryo. Each year a part of the meadows is flooded and re-colonized. Migration is an inevitable process in small mammal ecology. Recolonization was found to be a progressive process, resulting in heterogeneous distribution of small mammals in the floodplain. From summer to autumn densities increased and specimens could be observed on larger distances from the non-flooded areas. After the water had retreated, the flooded meadows had to be recolonized by root voles. Harvest mouse (Micromys minutus) and striped mouse (Apodemus agrarius) were trapped only in autumn. M. oeconomus was even more dominating in the wet meadow – 73% from total catch. |
