An approach to the edge effect in proof of the validity of Dice 's assessment lines in small‐mammal censusing

Abstract

Summary A second fieldwork for the sake of solving the edge‐effect subject was carried out in almost the same ways and plans in summer of 1971 in succession to that of 1970. It was found out that the population density was reduced to two‐thirds, but the data were sufficient to form the subsequent conclusions: The initial population estimated by the removal census method turned out to be well compatible with the numbers of survivals and emigrants of marked voles calculated by Jolly 's method. The natural, entire home ranges of both sexes reached by determining observed range length and width with 24 voles, selected on rigid conditions, agreed with those of the range‐conservative type in 1970 in both acreage and elliptic shape. In the majority of the select specimens, considered to reveal the natural ranges, the random distribution in number of captures per station within range was proved by means of I σ so far as such capture density as treated here is concerned. On the ground of the empirical evidence, the above range size approached by the routine observational method could be made surprisingly accordant with the range size in terms of r ‐values calculated by Wierzbowska 's method. From these proofs, the validity of Dice 's assessment lines makes evident, and besides, it could be further substantiated by use of Marten 's notion of mouse‐equivalents through the mediation of Wierzbowska 's method. Consequently, I have largely come to the conclusion that Dice 's assessment lines stand on justifiable basis from theoretical and empirical angles.