Comparison of estimates of numbers obtained by the methods of release of marked individuals and complete removal of rodents

Comparison of Estimates oiNumbers Obtained by the Methods of Release of Marked Individuals and Complete Removal of Rodents [With 7 Tables & 2 Figs.]The number of marked rodents present on a given day was estimated, taking into consideration not only their capture on that day, but also making use of information on their captures in preceding and following days (Calendar of catches method).These estimated numbers were compared with those estimated by means of the regression method when carrying out complete removal of the rodents in the same area.The mean difference in estimated numbers for resident individuals was 20.2%, and for all individuals caught in the study area 25.6°/o.It was demonstrated that there were differences in trappability among individuals from the same population and that entry of other individuals from the surrounding area takes place into the capture area.I. INTRODUCTION, STUDY AREAS The aim of the study was to compare estimates of the numbers of rodents obtained by two different methods.With the first method numbers were estimated on the basis of release of marked individuals, with the second, on the basis of complete removal of rodents.Investigations were made in the following areas: 1. in a forest and a meadow near the Field Station of the Institute of Ecology at Dziekanów Leśny.The wooded areas were composed of the following associations: Pino-Quercetum, Vaccinio myrtylli-Pinetum subass.molinietosum, Tilio-Carpinetum, Carici elongatae-Alnetum.The meadow formed a complex of the following associations: Glycerietum maximae, Caricetum elatae, Carici-Agrostetum, Stellario-Deschampsietum. 2. in the Mazurian Lake District near the Field Station of the Institute of Ecology at Mikołajki, in wooded areas consisting of Vaccinio myrtylli-Pinetum associations and several variants of the Pineto-Quercetum association. 3. on the "Crab-apple" island situated in Lake Beldany (Mazurian Lake District), where the following forest associations were distinguished: Solid-Franguletum, Circaeo-Alnetum, Tilio-Car pine turn 2 ).