The kinds of animals that live on island can help scientists figure out how those islands formed. The presence of amphibians, freshwater fish, and orangutans in Borneo, for example, indicate that an island was once attached to the mainland, because those kinds of creatures rarely cross large stretches of water.
Reptiles seem especially hearty in the face of long-distance ocean journeys. Salt-water doesn’t bother them, and they can go for long stretches of time without drinking anything. That probably explains how so many big tortoises and iguanas made it to the Galapagos Islands.
Wondering how life gets to secluded islands brings up another interesting question: Is there such a thing as a secluded island? Most specks of land on our planet have at least something living on them. But a volcano eruption, among other natural disasters, can wipe out life on an island, giving scientists a window into the colonization process. Krakatoa is one famous example. When the Indonesian volcano blew in August, 1883, it was one of the most violent volcanic eruptions ever recorded. The blast wiped out 75 percent of the land area of its island. Since then, scientists have carefully watched life rebound there.
Creatures that live on islands are especially vulnerable to extinction, because they often get used to life without predators. Modern-day movements of globe-trotting people has threatened island populations around the world in recent decades. As a result, island biogeography – the study of distributions of plants and animals on islands – is becoming an increasingly important type of conservation research.
And it’s not just islands in the sea that researchers are interested in. Secluded parks and mountaintops can act just like islands for species that need to get from place to place. Even people can be tools for the study of island biogeography. We host all sorts of parasites and bacteria, which migrate from person to person. Which means we might need to reassess the popular saying: “No man is an island.”