Second-generation rodenticides and polecats (Mustela putorius) in Britain.

In Britain, polecats Mustela putorius hunt around farm buildings, especially in winter, and, as a result, may be secondarily exposed to rodenticides by eating contaminated prey. This paper reports the first survey of second-generation rodenticides in polecats. Twenty-nine adult polecats which had been killed either accidentally on roads (24) and in traps (4), or had died of an unknown cause (1) were collected during 1992-1994. The livers of 24 animals and the stomach walls of the remaining five, for which the livers were not available, were analysed for difenacoum, bromadiolone, brodifacoum and flocoumafen. In total, rodenticide residues were detected in 31% of the polecats analysed. Residues were found in seven of the 24 livers (29%) and in two of the five stomachs analysed (40%). Difenacoum was detected most frequently (28% of animals), and was the only rodenticide in the stomach, while bromadiolone and brodifacoum were detected in only 10% and 3% of polecats, respectively. Flocoumafen was not detected in any animals. More than one rodenticide occurred in the livers of two animals; one contained difenacoum and bromadiolone, the other also contained brodifacoum. There was no sex bias in the proportion of animals containing rodenticides. Animals with detectable residues came from more than one county and were collected only during January-April in each year.