Estimation of rat population (Rattus norvegicus) and reducing their number in the urban environment

In the paper the authors consider traditional, modern and promising (at the stage of development and testing) methods of urban Rattus norvegicus population monitoring and activities on its numbers reduction. The analysis of rodent population assessment methods showed the absence of a universal method for determining urban rats number, which would take into account both ecological and biological characteristics of the species and the characteristics of a particular city, the territories of which may differ significantly in the ratio of residential, recreational, industrial and other areas. The main recommendation for monitoring organization is to assess the direction of change in the number of urban rats, determine reduction or increase trends of its population. Measures to reduce rat numbers in urban areas are divided into technologies to reduce the capacity of their habitat (preventive methods) and the actual deratization. A variety of deratization methods and its simultaneous using is not enough for complete extermination of rats in urban environment. High ecological valence of the species, peculiarities of human habitat and vital activity (including safety of people and non-target groups of animals) and other factors with low degree of prognosis (predetermination) lead to the absence of effective universal models of rats elimination in the cities of Russia and abroad. According to population biology, the task of reducing the number is not just to reduce it, but to prevent the «explosion» – the moment when generations of young rats come into reproduction (for most regions – this is midsummer). Acting on the rat population twice a year (May, July), it is possible to stabilize its number at a relatively low level. The main difficulties in the standardization of measures and preparation of regulations for the control of rats number in the urban environment are listed.