Fluctuations in population abundance in two anurans from Central Serbia

We monitored the population size of the agile frog (Rana dalmatina) and the common toad (Bufo bufo) from 2011 or 2012, respectively, to the year 2017 at a syntopic breeding site in the vicinity of Belgrade. Adult R. dalmatina population size had minor fluctuations during the years of study (from 351 to 108 frogs). On the contrary, the adult B. bufo population was widely fluctuating towards decline (from 1158 to 141 toads). In both species, population fluctuations were not significantly related to variation of meteorological parameters (air temperature, humidity, precipitation). Density dependence effects on population size were not detected in either species. Apart from possible effects of climate change, the indicated trend towards decline of the monitored B. bufo population could also be the outcome of common population fluctuations or of increasing anthropogenic impact (vicinity of settlement and agricultural land). More years of monitoring more than one population are required to obtain precise information. Nevertheless, our results seem to be coherent with other studies that recommend conservation action for this species