I think that you can test the deviation about the ratio 1:1 for male:female from your data set. Using Chi square to test that for your collected data. Otherwise, i do not think that there is a specific ratio assigned for each region especially if the population is fluctuated based on environmental and physiological parameters and it is going to be changed from time to time. Then, if you said under natural conditions, this is a huge question. I hope to find my answer as helpful.