The main sources of introduction are fish-breeding farms and medical and biological institutes, which are using this species in their own experiments. Several populations of R.ridibunda have been found in the city since that time.
Reproduction occurs only in the warmest years.
Similar processes occur in Nizhny Tagil - a city with heavy industrial contamination. Anecdotal reports date the appearance of this species in the city to 1978. During a survey in 1988, only one population was found in the city. Now, the lake frog inhabits 14 sites in the city area and reproduction has been noted in 10. The situation in Nizhny Tagil differs from that in Ekaterinburg as R.ridibunda is displacing native species of amphibia.