The records of sewer baiting work for three London boroughs were examined to see whether there were locations that exhibited 'rat' (Rattus norvegicus) activity more often than would be expected by chance, a feature we dubbed 'hotspots'. More than 100000 baiting records were checked covering 15 years of the London Borough of Enfield (Enfield) and 5 years each of the London Borough of Barnet (Barnet), and the Royal Borough of Kensington and Chelsea (RBKC). The additional boroughs were included for comparison to see whether any effect observed was confined to Enfield or was a feature that could be found in both inner and outer city locations. Each borough was divided into kilometre squares corresponding with those found both on Ordnance Survey maps and also Thames Water Utilities Asset maps. The number of records per square were logged and then the number of positive records for all the manholes in that square on a year-on-year basis. We examined 350 km2 in Enfield, 377 km2 in Barnet and 66 km2 in RBKC. The data were subjected to a weighted analysis (i.e. allowing for the number of manholes per square and the varying total rat population from year to year). Some areas were shown to exhibit significantly higher amounts of activity than others suggesting that their distribution is not random and that there must be environmental and other factors, which make certain locations attractive to rats. Squares with very high activity, repeating year-on-year, 'hotspots', were found in all three boroughs, suggesting that the phenomena are widespread.
This is a long-term study that investigates the dynamics of a population of Rattus norvegicus (Berk) inhabiting a sewerage system in London. Thirteen years (1986/7-1998/9) of data from sewer baiting records were analysed (a total of 35,478 records). Manholes were baited with the anticoagulant Brodifacoum (0.005%) on a pinhead oatmeal bait base. Time series analysis was conducted on the data set to determine the underlying trend of the data and the population fluctuations about this trend. An exponential curve was found to give an accurate and realistic fit to the data and indicated that the rat population had decreased over the study period. Decomposition analysis indicated a 5-year cycle best described fluctuations around this trend.
Sewer Rats (Rattus norvegicus) are opportunist occupiers of parts of underground sewerage networks. Their occupation in part depends upon their ability to scavenge food particles from faecal matter in the sewer flow. Food Waste Disposal Units, also called Garbage Grinders or Waste Macerators, are relatively uncommon in the United Kingdom (UK) but may become more common as pressure is put on other methods of waste disposal. Since these units put undigested food into the sewer network, some assessment needed to be made on any potential impacts on the sewer rodent population. This is important since policy relating to the acceptance of waste disposal units (WDUs) was based upon outputs. A selection of WDUs were acquired and a series of standardised tests were performed on a variety of food groups to assess whether the output of these units would represent a potential food resource for rats in sewers.
These results are presented graphically in the text, and show that a large proportion of the output would be available to rats.
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