Population Densities of Small Mammals in Open Field Habitats in South Sweden in 1964-1967

Abstract

The abundance of small mammals was investigated in an abandoned field and in a pasture in southern Sweden in 1964-67 by removal trapping with trap lines. Microtus agrestis was the most common small mammal in both habitats. It was most abundant in the abandoned field where it increased after a crash during spring 1964 with less than 5 animals per ha to a peak in autumn 1966 with about 60 animals per ha. During summer 1967, after a new crash, there was a very rapid increase to about 50 animals per ha. Apodemus sylvaticus was most abundant in the pasture with a peak density of 5 animals per ha. Sorex araneus showed greatest density in the abandoned field, varying between approx. 3 and 10 animals per ha. In the rodent species there were pronounced peaks in October while the lowest density was normally found in March-April. S. araneus showed peaks either in October or in the middle of the summer. Pe3loMe H4ccxIegOBanacb 'mCJeHHOCTb MeJIKHX MjieKOIIHTaioIUIHX Ha 3a6poLiieHHbIx IIOJI5X H Ha naCT6Hiuax B IONCHOIR IJIBeIHH B 1964-67 rogax MeTOAOM UOBTOPHOrO OTJIOBa. Microtus agrestis HaH6oJIee o6bIHbIEA BHA B o6oix MeCToo6HTaHHIfX, OH HaH6OJIee MHOrO'IcJIeHeH Ha 3aneKH. fnocnie BCnaIIaIUK BeCHOA 1964 roga IIJIOTHOCTb XCHBOTHbIX CTana HH)Ie 5 3K3/ra, oceHbWO 1966 r. oHa so3pacJIa xro 60 3K3/ra. JIeTOM 1967 r. IIJOTHOCTb 6bICTpO yBenJiaWIHnCb np1MepHO Ao 50 3K3./ra. Apodemus sylvaticus HaH6onIee o6HIneH Ha naCT6HTie c MaKCHMaJIbHOil IJIOTHOCTbO 5 3K3.fra. Sorex araneus HMeeT HaHBbICMYIO HIIOTHOCTh Ha 3anJ1ew 3-10 3K3/ra. Y rpMl3yHOB 3aperHctpHposaH 3aMeTHM161 HH1X 'IHCJIeHHOCTH B OKTI6pe H MHHHMajibH6 H qHCjieHHOCTh B MapTe-aInpeJie. S. araneUs HMeeT 1IHK qiCJceHHOCTH JIH60 B OKTI6pe, irn6o B cepeARHe JIeTa. Manuscript accepted October 1967.