Which animal acts like a bulldozer?

In the sands of tropical reefs lives a tiny little fish called a goby. Gobies would make a tasty snack for passing predators, so to keep from being eaten, they live in holes dug into the bed of the reef. There’s just one problem: gobies can’t dig holes with their tiny fins! Fortunately, there is a solution: gobies live with a roommate called a bulldozer shrimp!

Bulldozer shrimp use their massive claws to push sand and rocks out of the way, just like a bulldozer does, and they never stop digging, but they’re also mostly blind and can’t see approaching predators. Gobies have good eyesight but can’t dig holes. So gobies and bulldozer shrimp work together.

The goby sits at the mouth of the hole it shares with the bulldozer shrimp and keeps an eye out for predators. The bulldozer shrimp moves back and forth, shovelling rocks and sand from the hole. But as it moves, it keeps one of its antennae on the goby so that it can find the hole again. If a predator approaches, the goby shivers a warning and the bulldozer shrimp knows to duck back into the hole, with the goby right on its tail!

The gobies snatch up passing prey that pass by the hole, but the shrimp eats from a patch of algae grown next to the hole, which is easy to find and close enough that the shrimp doesn’t get lost. But if the blind shrimp does stray too far from the hole, the goby will swim out and guide it back to safety!