Polecat predation on frogs and toads at breeding sites in western France

Surveys of eight radiotracked polecats (Mustela putorius) showed that they caught mainly male terrestrial anurans at spawning sites. Agile frogs Rana dalmatina formed 77.5%, whereas common toads Bufo bufo represented only 14.6% of preyed anurans. Throughout the breeding period, male anurans were found to be predominant, representing 64.8% of available agile frog and 60.7% of common toad populations in the four ponds studied. The number of male frogs was significantly higher in two ponds which were not exploited by polecats in 1990. Polecats preyed selectively on anuran males (electivity index D = 0.34 in agile frogs and D = 0.50 in toads). Thus, the intensive predation of polecats at spawning sites can influence the sex-ratio of anuran populations.