Parasitic robot controls turtle it's riding by giving it snacks

In preparation for becoming humanity's overlords, robots have started controlling turtles. By first getting the reptiles to associate a red light with food, the shell-attached robots can dictate where the turtle moves around a tank, creating a rather unusual parasitic relationship. Even with the huge progress made in recent years, robots still have some serious limitations. Making their motion robust enough to survive the rigours of daily life is an ongoing battle, as is the puzzle of providing them with enough energy to avoid spending hours recharging. Nature, on the other hand, can do this easily.