Living with Mammals survey

Quality Control

Records are submitted voluntarily by members of the public with a wide range of expertise. Sightings are not verified and species may be misidentified (with a specific risk: high in the case of mouse or vole species, and low in the case of badger or hedgehog, for example). For medium-sized species, confidence in identification is medium to high, apart from polecat sightings which could be ferret or polecat/ferret hybrid. Taxonomic coverage is biased towards more visible species (larger and/or diurnal ones). Small differences in survey effort at night or around dawn/dusk may strongly affect counts. All records have been checked using the NBN Record Cleaner.

Method steps

1. The data are from a public-participation survey: data are collected by volunteers at sites (chosen by participants) within 200m of a building or wholly within a town or city (e.g. large civic parks). Nature reserves and urban farms are excluded. Direct observations of mammals or of field signs are recorded and counts of the maximum number of individuals seen together at one time in a particular week given. Records are submitted online by the participants or sent in on paper forms and added by the survey coordinator.

Records are collected from sites in the ‘built environment’ (defined as within 200m of a building) anywhere in Great Britain. The distribution of records mirrors the distribution of returns (i.e. sites are not randomly selected), which in turn matches the distribution of built land. The majority of survey sites (and hence records) are located by a post code from which a six-figure grid reference is derived The majority of survey sites (and hence records) are located by a post code from which a six-figure grid reference is derived.