Rat Control in Alberta

A rat control program, administered and coordinated by Alberta Department of Agriculture, has kept Alberta essentially free of Norway rats (Rattus norvegicus) since 1950. A control zone, 29 x 600 km, along the eastern border prevents rats from moving into Alberta from the east. Sporadic rat infestations within the interior of Alberta are reported by concerned citizens and eradicated by government personnel. Strong support for the program by citizens and local governments was developed through public education and information. The program has been successful for a variety of reasons including geography, climate, legislation, availability of warfarin, the relatively small size of the infested area, grass roots support, lack of complacency, and the personnel involved. Norway rats were introduced to the east coast of North America about 1775 and gradually spread westward over most of the continent, their distribution being closely associated with the habitation of man (Hall and Kelson 1959). Rats entered eastern Saskatchewan about 1919 and extended their range to the northwest at about 24 km (15 mi) per year (W. Lobay unpubl. data). Rats were first reported on the eastern border of Alberta in 1950, and would have continued to spread westward were it not for a rat control program that halted their advance and continues to maintain an essentially rat-free Alberta to date--more than 33 years later. This paper describes the evolution, history, and current status of the rat control program in Alberta, and discusses factors which contributed to the success of the program. Data were obtained from Alberta Department of Agriculture (ADA) annual reports, 1949-73, ADA Plant Industry Division annual reports, 1974-81, and from the files of J.B. Gurba, Head, Crop Protection Branch, ADA. THE EARLY YEARS, 1950-53 Norway rats were first discovered on a farm near Alsask on the eastern border of Alberta during summer, 1950 (Fig. 1). The discovery was made by field crews from Alberta Department of Health, engaged in studies of sylvatic plague (Yersinia pestis) in Richardson's ground squirrel (Spermophilus richardsonii). Provincial authorities were initially concerned that rats might spread plague throughout Alberta, although they were also aware of the economic destruction caused by rats. Consequently, the Alberta government decided to halt or at least slow the spread of rats to the west. In 1950, responsibility for rat control was transferred from Alberta Department of Health to ADA, Field Crops Branch, much to the distress of some senior officials in the former department. ADA was probably the better choice to administer a rat control program because the affected area was predominantly rural, and ADA specialized in extension and was better staffed and organized in rural areas. Existing legislation also authorized ADA to control pests of agriculture. The Agricultural Pest Act of Alberta, 1942, authorized the Minister of Agriculture to designate as a pest any animal that was likely to destroy crops or livestock. The act further stipulated that every person and every municipality had to destroy and prevent the establishment of designated pests. (A municipality is a local government within Alberta and includes cities, towns, and counties or comparable rural governments). Where pest control was not considered adequate, the provincial government could carry out the necessary measures and charge the costs to the landowner or municipality. Thus, legislation that mandated control of pests by every person and every level of government was in place before rats ever entered Alberta, and became effective when rats were declared a pest in 1950. An amendment to the act in 1950 further required that every municipality appoint a pest control officer (PCO). William Lobay, Supervisor, Crop Protection, ADA, originally conceived the idea of a buffer control zone to prevent rats from spreading into Alberta, and was initially responsible for organizing, supervising, and administering the program during 1950-53. Most people in Alberta had had no contact with rats and, consequently, did not know what rats looked like or how to control them. Thus, the government's initial response was to educate the public, outline program objectives, and obtain support from local governments and residents. ADA encouraged local municipalities to appoint PCOs and agreed to: a) coordinate and supervise the rat control program, b) aid any local programs undertaken by any organization, c) provide printed material for information and education campaigns, d) provide poisons to local PCOs, and e) provide additional assistance (financial, equipment, etc.) to any municipality where such support would significantly aid in the extermination of rats. 1984, Proceedings Eleventh Vertebrate Pest Conference (D.O. Clark, Ed.). Printed at Univ. of California, Davis, Calif. 64 Fig. 1. Distribution of Norway rats in eastern Alberta, 1950-58. Preserved rat specimens were distributed to ADA offices to aid in the identification of rats in the 1950s. In 1951, five provincial PCOs whose primary responsibility was weed inspection, provided training and assistance to municipal PCOs. Inspectors from Saskatchewan Department of Health, familiar with rats and rat control, also assisted with training. Conferences on rat control were held in six towns in eastern Alberta and 2000 posters and 1500 mimeographed pamphlets, "Rat Control in Alberta, 1951", were distributed to elevators, railway stations, schools, post offices, and private citizens. "Rat Control in Alberta, 1951," advocated destruction of rats, elimination of rat harborages and food supplies, and rat-proofing of buildings, principles which are still valid and basic for rat control today. Recommended toxicants were red squill, antu, barium carbonate, zinc phosphide, 1080, thallium sulfate, arsenic, strychnine alkaloid, and warfarin. In 1951, warfarin was still a new and relatively untried toxicant. By fall 1951, 30 rat infestations had been confirmed along 180 km of Alberta's eastern border, and in 1952, rats were active along 270 km of border. Most infestations were within 10 to 20 km of the border although rats had penetrated 50 to 60 km westward in three areas (Fig. 1). Alberta did not have the expertise to control rats and probably could not have developed the expertise in time to halt the movement of rats to the west. Thus, a private pest control firm was contracted to control rats until ADA could develop an effective program. During June 1952-July 1953, 63,600 kg of 73% arsenic trioxide tracking powder was used to treat 8,000 buildings on 2,700 farms (24 kg/farm; 8 kg/building) in an area 20 to 50 km wide and 300 km long between Medicine Hat and Provost (Fig. 1). Tracking powder was blown underneath all permanent buildings within the control zone. While only permanent buildings were supposed to have been treated, some temporary structures were treated as well. Tracking powder was exposed in some areas where the treatment was haphazard or where temporary buildings were moved or torn down. In addition, some residents were not informed that arsenic was being used, and some, allegedly, were told that the tracking powder was only harmful to rodents. Consequently, some nontarget poisoning of livestock, poultry, and pets occurred for at least the first 2 to 4 years after treatment. As a precaution, ADA sent letters to all residents in the control zone each year through 1955, warning of the dangers to humans, livestock, and pets. The poison-proofing program was expensive, costing $152,670 (Canadian) for 1952-53, of which 74% was for tracking powder. Annual cost of rat control did not exceed this figure until 1978. Consequently, the poison-proofing program was discontinued because the cost was considered to be too high