Scientists have long known that certain pesticides, industrial chemicals and heavy metals have a detrimental impact on the reproductive health of a wide range of species (including humans) by disrupting the endocrine system. As exposure to, and the effects of, ‘endocrine disrupters’ are likely to be more pronounced in wild species with a short gestation period and life-cycle we have chosen to develop non-invasive tools based upon faecal steroid analysis to monitor the reproductive status of the short-tailed field vole (Microtus agrestis). This approach is hoped to eventually provide a sensitive means of detecting environmental disturbances that could adversely affect humans, livestock and wildlife by establishing the the field vole as a terrestrial biomarker. Faecal steroid hormone analysis has already been demonstrated as being a convenient and reliable means of diagnosing reproductive state in a large range of mammalian species (including gazelle, rhino, macaque and mice), however, as of yet little is known regarding the hormonal changes that occur during pregnancy in M. agrestis.