Rodenticides

The second-generation anticoagulants, brodifacoum, 

bromadiolone, difethialone, difenacoum and flocoumafen, are 

acutely toxic and have long biological half-lives. Therefore, in 

the ‘risk hierarchy’ they present the greatest risk to non-target 

animals and the environment. There is evidence that they may 

cause the deaths of non-target animals and they are widely 

present in the environment in the bodies of many non-target 

species, some of high conservation value such as barn owls, 

red kites, kestrels and peregrine falcons. They should be used 

only when other methods of achieving rodent control have 

been carefully considered and found to be unable to provide an 

effective solution to the rodent pest problem present at the site. 

It is not possible to rank these compounds in respect of risk. 

However, resistance to bromadiolone and difenacoum, among 

both Norway rats and mice, should be considered when deciding 

which of the five compounds to use.

In order to deter rodent infestations, sites should be cleared 

of all debris, rubbish, old machinery and equipment, unwanted 

stores of straw and hay, etc. Vegetation should be cleared 

around buildings to provide an open perimeter and immediate 

surroundings, so that natural predators can take rodents. If 

possible, areas around buildings may be laid to concrete, or 

other hard surfaces, to prevent rodent burrowing. Once again, 

the only non-target impacts of such operations will be on the 

other animals that rely on the materials taken away for cover and 

harbourage. For example, straw and hay bales are best removed 

during winter because they often provide breeding sites for barn 

owls