Rats in an Agricultural Landscape: Population Size, Movement and Control
thesisposted on 09.07.2010, 12:17 by Malcolm Brown
This research investigated the effects of coordinating rodent control across areas up to 400 ha, using conventional and alternative strategies, to see if it was possible to reduce rat numbers and to keep them at a lower level compared with uncoordinated control. The aims were to reduce the rat numbers, reduce the amount of rodenticide used over time and to reduce the risk of secondary poisoning of non-target animals. Rodenticide loads in rat carcasses were investigated using historical and new samples from Berkshire, Leicestershire and Yorkshire in order to quantify risk to non-target predators of rats. Movement was also studied to see if rats were moving into farmyards in the autumn and out in the spring as is generally assumed. Analysis of radio-tracking data showed that the majority of rats tracked stayed within a small home range, two moved and stayed away from the trap site and only one moved into a farmyard. Analysis of the movement of the rats caught in traps showed that the movement towards and away from farms was in roughly equal numbers. The rodenticide analysis showed that rats from areas of rodenticide resistance carried a far greater body load of poison than those from non-resistance areas. Thus resistance increases the risk of a predator or scavenger of rats ingesting a lethal dose more quickly in areas of rodenticide resistance. The coordinated rat control was broadly successful over a period of two to three years. Rat numbers varied greatly between Yorkshire and Leicestershire, with Yorkshire having the larger numbers. Rat control in the coordinated areas showed a decreasing trend over the period. Bait take also generally showed a decline over the period. The results revealed an apparent delayed synchrony in rat numbers between coordinated and uncoordinated areas in Yorkshire that requires further investigation to explain.