Responsive robotic prey reveal how predators adapt to predictability in escape tactics

To increase their chances of survival, prey often respond to predators by being unpredictable when escaping, but the response of predators to such tactics is unknown. We programmed interactive robot-controlled prey to flee from an approaching blue acara predator (Andinoacara pulcher), allowing us to manipulate the predictability of the preys initial escape direction. When repeatedly exposed to predictable prey, the predators adjusted their behaviour before the prey even began to escape: prey programmed to escape directly away were approached more rapidly than prey escaping at an acute angle. These faster approach speeds compensated for a longer time needed to capture such prey during the subsequent pursuit phase, and predators showed greater acceleration when pursuing unpredictable prey. Collectively, these behaviours resulted in the preys predictability having no net effect on the time to capture prey. Rather than minimising capture times, predators adjust their behaviour to maintain an adequate level of performance.