Methods of Laboratory Toxicological Investigations on the Common Vole (Microtus arvalis [Pallas])¹

Abstract

This paper reports on some laboratory methods for evaluating the toxicity of rodenticides to the common vole. Test conditions including the experimental animals used, their housing, feeding and handling (measuring body weight, marking of the individuals, route of administering the toxicant), test materials and observations are presented. New toxicants were screened simultaneously on white rats and on voles. For each compound, the following data were determined: a) the acute (single dose) approximate LD50 (= ALD50), b) the acute (single dose) LD50, as well as the multiple dose toxicity for anticoagulants, c) the approximate 5‐day LD50 and d) the 5‐day LD50. For the determination of a) and c), about 6 animals were used. The LD50 values were determined by giving 6–8 doses to each of 10 rats and 4 doses to each of 4–6 voles. A brief report is given on the determination of the joint toxic action of the 2 chemicals. Rodenticidal formulations were tested on voles in various no‐choice and choice feeding tests. No‐choice tests with compounds having an acute toxicity were carried out for 24 h, those with anticoagulants for 5 × 24 h and those with narcotics for 2 × 24 h. The corresponding periods for choice tests were 2 × 24 h, 5 × 24 h and 4 × 24 h, respectively. Preference and repellency tests were also carried out. The stability of a rodenticide in baits exposed to weather, as well as the effectiveness of fumigants on solid carriers were investigated under simulated environmental conditions.