Humans have explored the entire face of the planet, but we haven’t done so alone. Animals and plants came along for the ride, some as passengers and other as stowaways. Today, these hitchhikers pose one of the greatest threats to the planet’s biodiversity, by ousting and outcompeting local species.
Islands are particularly vulnerable to invaders. Cut off from the mainland, island-dwellers often evolve in the absence of predators and competitors, and are prone to developing traits that make them easy pickings for invaders, like docile natures or flightlessness.
Two years ago, I wrote about the ability of invasive predators to change entire island landscapes. In the Aleutian archipelago that runs between Alaska and Russia, Arctic foxes have turned some islands from grassland to tundra by killing the seabirds whose droppings provided the islands’ only fertiliser.
Now, we return to the ill-fated Aleutians to discuss another study that shows how the actions of immigrant predators can even domino into the surrounding waters. This time, the stars are not foxes, but that other ubiquitous opportunist – the brown rat.