Density estimation for an urban population of the field mouse

Abstract

W skaźniki zagęszczenia m iejskiej populacji myszy polnej Jacek GOSZCZYŃSKI Goszczyński J., 1979: Density estim ation for an urban population of the field mouse. Acta theriol., 24, 31: 417—419. The density of the field mouse Apodemus agrarius (Pallas, 1771) was estimated twice during the course of a year, using the Petersen index, in one of the green spaces of Warsaw. The densities obtained, 88 and 39 individuals/ha, are higher than those given for areas outside towns. The biotic and abiotic factors responsible for such high densities are discussed. [Agricultural Univ., Dept. Game Management, Rakowiecka 26/30, 02-528 Warszawa]. The aim of the study was to estim ate the density of the field mouse, Apodemus agrarius (Pallas, 1771) in a habitat formed by one of urban green areas. Papers so far published on such habitats have either been faunistic in character (Sumiński, 1922; Chudoba et a I., 1961) or supplied inform ation on relative density (Andrzejewski et al 1978). In order to estim ate possible epidemiological or trophic role of this species in a town it is necessary to have an idea about its real den­ sities. The study area was situated in the Greek Orthodox cem etery in W arsaw, lying w ithin the limits, but outside the centre of the city. The cem etery is adjoined by extrem ely busy streets, a housing settlem ent and a park. Density estim ates were carried out in the southern part of the cem etery in June and October 1977. The area is covered by trees more than 80 years old, and a dense herb layer which is sim ilar to the Tilio-Carpineturn habitat in resipect of species composition and struc­ ture. The southern part except for its centre is rarely visited by humans and the herb layer only rarely m own in certain parts. live traps were placed in a basic grid (40X40 m) over the w hole of the southern part of the cem etery, occupying an area of 5.25 ha. A total of 42 trapping sites were set up and tw o traps placed on each of them. The trapping cycle consisted of 6 (June) and 7 (October) inspections of the traps, during w hich the m ice w ere marked and released. The traps were inspected tw ice daily in June and once daily in October. The last two inspections of each trapping cycle were used to estim ate the percentage of marked mice. The number of all individuals present in the area was estimated by the Petersen index* (Petersen, 1896). In order to reduce the rodents, habituation to traps to a minimum (and to avoid constantly catching the same individuals) the traps were moved round the basic trapping sites during in