Continuously Variable Proportional Circle Map

This image, taken from http://www.ugandatravelguide.com/mountain-gorillas-bwindi/gorilla-tourism-bwindi.html, illustrates gorilla populations in Bwindi. The size of each circle is proportional to the population present in the location. The text that accompanied this graph tells us that the overall population of gorillas in the region is 300, however, no frame of reverence is provided to judge the population of a particular circle.