Factors influencing molehill distribution in grassland: implications for controlling the damage caused by molehills

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The authors examined the possibility of controlling molehill distribution by using management procedures that alter the availability of earthworms, the principal food of moles (Great Britain), as an alternative to using poisons and traps. They monitored abundance of molehills and earthworms over two years in an acid grassland where treatments of pesticides, grazing (by rabbits), soil pH, herbicide, and fertilizer were imposed. In the experimental area (4,608 m2), 1,062 molehills formed, each with an average area of 0.14 m2, meaning a disturbance rate equivalent to 3.2% of the soil surface over two years. Peak molehill production occurred in spring and autumn, with a few hills formed at other times of year. Molehill production in grazed areas was one-third that of hay meadows. Half as many molehills formed in unlimed as limed plots. Significantly fewer molehills formed in areas where grass species were removed (herb-rich) than in areas where no species were removed. Insecticide, molluscicide, and fertilizer application had no significant effect on molehill production. The treatments that had fewer molehills also had fewer earthworms, indicating that molehill production was decreased, indirectly, through the treatments reducing food availability. Reducing the number of molehills through management procedures that decrease earthworm availability offers an alternative to lethal control of moles. This decrease could be achieved by allowing or encouraging soil pH to fall (e.g., withholding lime application, using acidifying nitrogen fertilizers), by creating herb-rich swards, or by preventing plant biomass from accumulating for long periods. These methods would be more applicable to gardens, sports fields, and nature reserves than to farms, where conflicts with normal farming practices make them difficult to implement.

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ELECTRONIC FILE - Zoology