Most starfish look small, slow, and harmless. Crown-of-thorns starfish are different. They can grow up to two feet across, sprout up to 21 arms, and are coated in dense venomous spines. They eat coral - and they’re very good at it.
A crown-of-thorns starfish climbs onto a coral, pushes its entire stomach out through its mouth, and drapes it over the coral’s surface. The stomach digests the soft coral animal from outside. When the starfish moves on, all that’s left is the bare bone-white skeleton of the coral.
Normally a reef can handle a few. But every so often a population boom happens, and thousands of starfish swarm a single reef at once. They can strip the Great Barrier Reef of huge sections in months. Today, divers and underwater drones hunt them down one by one to keep numbers in check.
