DEFRA does not have data on the size of the UK rat population.
Data on rodent infestation in domestic dwellings are obtained from the English House Condition Survey (EHCS). The detailed findings for 2001 are summarised in the report ‘Rodent infestations in domestic properties in England, 2001’. The EHCS only provides an estimate of the proportion of dwellings with rat infestations inside or outside. It does not provide definitive data on numbers of rats.
The 2001 report indicated that there may be a higher occurrence of rats within urban and rural areas when compared to suburban areas.
In May, DEFRA published an interim report on rodent presence in domestic properties from the EHCS data for 2002-03 and 2003-04. The key findings were that the occurrences of rats in these years are not significantly different from those observed in 2001.
A further detailed report is anticipated for publication in spring 2009.