Local amphibian populations at the edge of a species range are possibly of greater conservation concern than any other amphibians group. They experience greater demographic fluctuation than populations at the core of the range. We detected the most suitable distribution range of R. macrocnemis by maximum entropy (MaxEnt) method at the end of the southeastern edge of natural distribution range to find out which environmental variables have a significant role in determining the distribution pattern of this species in marginal populations. According to the map constructed, three important variables had a high contribution to species presence as land cover (63.4%), annual precipitation (27%), and precipitation of coldest quarter of the year (5.4%) variables. Then, we described new methods for estimating detection probability for terrestrial frogs, specifically R. macrocnemis. Finally, we estimated the population size of mountain frogs by calculated detection probability. Our repeated capture–re-capture (RCR) results suggest that the estimated detection probability for R. macrocnemis is: p = 0.052 . Thus, the total average number of R. macrocnemis obtained from the 17 habitat sites is 982.5 adults (range: 708–1211 adults). In conclusion, the population estimates by detection probability index are generally much higher than densities reported for the Mountain frog populations than visual encounter estimation about 50.5 adults (range: 37–63 adults).
