Investigation into the use of field edges by small mammals on the Writtle College Estate margins generally served to expand a habitat already present and did not add a habitat type to the existing situation. It was also noted that during the four trapping sessions the fields were ploughed earth or contained immature crops. Fig. 1. Total numbers of animals captured in sections with and without uncultivated margins. Fig. 2. Numbers of Wood Mouse, Bank Vole and Common Shrew captured in autumn and spring. Fig. 3. Numbers of mammals from the different locations within the uncultivated margins. Essex Naturalist (New Series) 21 (2004) 77