Difficulty in Visual Sex Identification: a Case Study on Bank Voles

Abstract The present study aims at quantifying the error in visual sexing of live-trapped bank voles and evaluating if animal body weight and experience of field workers affected the ability to determine the sex of voles. The error in sex attribution involved 25.6% of non-reproductive individuals, pointing out the need to validate the field sex identification. Body weight of voles did not affect the ability of trappers to visually discriminate the sex of animals. Field workers had similar percentages of error independently of their expertise in vole sexing but they also showed a sex-bias in wrongly sexed individuals.