Moles are not legally protected in the United Kingdom and are regarded as pests, causing damage to lawns and commercial and agricultural land. Mole tunnelling in freshly planted fields can compromise plant roots often causing plants to die, damaging harvest numbers. Mole hills cause damage to domestic lawn mowers and farm machinery, also causing contamination of grass used to make silage. Through the 19th and 20th century moles were trapped in large numbers for their pelts but today they are killed as pests. This is done by humane trapping. The use of strychnine hydrochloride for poisoning moles or any other animals is illegal.