The results of studies conducted by the sanitary and epidemiological service in the Voronezh region from 1959 till 2013 were analyzed. Records of small mammals (SM) were carried out by snap traps with wire hooks for baiting. Standard bait (black bread pieces flavored with sunflower oil) was used. Traps were placed in lines. The numbers of SM were calculated as a percentage of animals fallen into 100 traps per day. The data obtained were analyzed using conventional statistical methods, including the method of standard deviations.