Many species of animals on islands are larger than related species on the mainland. Scientists hypothesize that this phenomenon, called island gigantism, evolved in response to the scarcity of competitors and predators on islands. Reduced competition and predation allows species to exploit more resources and frees them from the need to hide in small refuges. The graph shown here compares the average carapace (shell) length of mainland and island tortoises. Summarize the results, then use the data to predict whether the surface area to volume ratio is higher in mainland or island tortoises.