20-YEAR EXAMINATION OF THE HABITATS OF AN URBAN NORWAY RAT, RATTUS NORVEGICUS BERK. (MAMMALIA: MURIDAE) POPULATION

Abstract:
In 1971-72 a large-scale, city-wide campain against Norway rat was carried out by Bábolna Bio in Budapest. The rat infestation rate of premises fell to an average level below 0.5%. Subsequently a complex maintenance program was undertaken. This comprised preventive and curative measures based on data collection of reports or regular surveys as well as targeted placements of poisonous baits. In baits as active ingredients coumatetralyl and, since 1990, bromadiolone selectively acting anticoagulant compounds were used. Annual rat infestation rates further decreased having attained a minimum 0.08 % yearly level in 1998. The habitat preference of Norway rat in various urban biotops of Budapest was studied. A categorization and code system complex habitats and micro-habitats was elaborated. Since 1978 a computer-assisted, database of rat occurrences in different habitats has been established, and data from a 20-year period (1978-1997) are presented here. Simultaneously with a declining Norway rat occurrences, the overall pattern of habitat preference did not change. Apartment buildings were primarily preferred by rats followed in the order of incidences by family houses, non-food industrial units, public services and open fields, food industrial units and, finally, by public institutions complex habitats. Courtyards and surroundings were frequently inhabited sites, often with extensive underground burrow systems. The rodents colonized different parts of the sewerage system, and in buildings they preferred cellars. Noticable fluctuation of rat incidences were characteristic first of all for family house complex habitat and for the micro-habitat group of the sewerage system.