BIOLOGY AND CONTROL OF THE COAST MOLE, SCAPANUS ORARIUS ORARIUS TRUE, IN BRITISH COLUMBIA

Abstract

Coast moles were studied and trapped from 1935 to 1945 at Agassiz, British Columbia. They cause economic damage in the lower Fraser Valley by injuring growing crops and by covering up to 15 per cent of the surface of a field with their hills.The moles ate almost any arthropod, annelid, or molluscan that they captured, but earthworms comprised 93 per cent of the stomach contents. Adults ate nearly twice their weight in earthworms daily, or 100–150 grams, representing more than 100 worms. The populations of moles apparently varied in proportion to those of the earthworms.The moles mated from January to early March. The young were born in March or April. Yearling females had two embryos; 2-year-old females had three; and mature females had four. Of 940 trapped during the winters, 45 per cent were over 1, and 6 per cent were over 3 years old. The average weight of mature 74 males was 74.3 ± 5.6 grams; the average weight of 30 mature females was 69.8 ± 4.1 grams.Natural control was ineffective. The disastrous Fraser River flood of 1948 lowered the numbers significantly, but recovery was rapid.Artificial controls tested included: poisons, caustic irritants, explosives, flooding, earthworm poisons, combinations of chemical fertilizers and irrigations, mechanical and chemical barriers, commercial mole destroyers, poison gases, deterrents, and traps. Only the last two were of value; crude flake naphthalene was a deterrent, and the scissors type was the most effective trap. In heavy infestations as many as three moles per man-hour were trapped. Naphthalene was expensive but protected small plots for up to 6 weeks. For economic control by trapping an area of 300 to 500 acres should be trapped in one season. Smaller areas are quickly reinfested, since the moles travel up to 1 mile.