. The Canadian field-naturalist. January-March, 1954] The Canadian Field-Naturalist 11 THE EFFECT OF AND OIL ON MUSKRATS ''' L. E. Wragg Madison, Wisconsin. Introduction IN 1946, the Ontario Department of Lands and Forests initiated a study of muskrat numbers in the 800-acre Dundas Marsh, part of a game preserve near Hamilton, Ont. In this marsh in 1944, game overseer G. Beattie and other interested naturalists estimated the muskrat population at 5,000. In August, 1945, under supervision of the Hamilton Department of Health, a 3% solution of in fuel oil and kerosene was sprayed a
. The Canadian field-naturalist. January-March, 1954] The Canadian Field-Naturalist 11 THE EFFECT OF AND OIL ON MUSKRATS ''' L. E. Wragg Madison, Wisconsin. Introduction IN 1946, the Ontario Department of Lands and Forests initiated a study of muskrat numbers in the 800-acre Dundas Marsh, part of a game preserve near Hamilton, Ont. In this marsh in 1944, game overseer G. Beattie and other interested naturalists estimated the muskrat population at 5,000. In August, 1945, under supervision of the Hamilton Department of Health, a 3% solution of in fuel oil and kerosene was sprayed at one gallon per acre over the southern border of the marsh and nearby ravines to control mosquitoes. The following winter interested naturalists saw fewer than 30 houses in the marsh. The popular explanation of this decrease was expressed by an editorial article which appeared in the Hamilton Spectator in the summer of 1946. "... Parks Board officials stated today it had been brought to their at- tention that the spray was killing the musk- 1) From an thesis submitted to the Department of Zoology, University of Toronto. 2) Received for publication October 27, 1952. rats in the marsh. For years the marsh has been the breeding grounds for muskrats in this district. After breeding in the marsh they journey up the streams into a wide area around Hamilton and provide farmers and trappers with a fairly lucrative source of in- come. Their numbers however are reported decreasing due to death from the spray- ed on the marsh ..." Observations A four month study of the area in 1946 showed the habitat apparently excellent with no reason to believe food shortage, drought, pollution, severe winter, predation, or migra- tion was responsible for the decline that had occurred. apparently had no effect. Less than 1/5 the marsh was sprayed, and this only once in 1945. The following year it was sprayed three times but the muskrat population in- creased. Effect on othe
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