A monopoly win isn't always good — what happens when one species takes over

Snake Island, Christmas Island, and Ireland's Saltee Islands, all show what happens when ecological balance tips and a single organism becomes just a little too successful

Christmas Island: during the annual red crab migration, millions of crabs emerge at the same time, halting road traffic and covering the ground in a thick carpet of crabs

Islands are nature’s laboratories — small, isolated, and prone to evolutionary experiments that would never be allowed on the mainland.

Remove a few predators, limit the competition, and suddenly one species can find itself running the entire neighbourhood. Around the world there are islands effectively governed by crabs, mice, snakes, penguins, and rabbits. These places are often amusing and even occasionally alarming. They show what happens when ecological balance tips and a single organism becomes just a little too successful.