The Study of animal communication has a long and colorful history. In the 1950s Dutch biologist Niko Tinbergen collected stickleback fish and carefully observed how they interacted. He noticed that the abdomen of male fish would flush bright red during breeding season, as the fish built nests and established their territories. This color served as a warning signal to rivals—so much so that Tinbergen found that territorial males would lunge at any object with a similar hue, including wood blocks he held outside their tank and even a mail van passing by the laboratory window.