HarveyHenkelmann; Wikipedia

Why should an animal that wants to avoid being eaten have a bright white patch on its rump?

Rabbits are one of the many animals that have the apparently contradictory features of carefully camouflaged coats and hugely conspicuous rump patches that appear when the animals flee predators.

Dirk Semmann, an evolutionary biologist at the University of Göttingen in Germany, thinks he has the answer to this puzzle — and the evidence to back it up. Other theories hold that rump patches are warning to other animals, are sexually selected, or serve to show a predator that they have been spotted.

Semmann’s research suggests that these spots actually confuse predators because of their very noticeable nature. By focusing on the bright spot, the would-be predator ignores the larger body of the animal. Then, when the rabbit executes a sharp turn, the spot disappears and the predator has to readjust to focus on the camouflaged coat, losing vital seconds.

“The idea first appeared when I was running,” says Semmann. “I met this rabbit; it was always running and turning at some point. That got me thinking about the problem.”

To test his theory Semmann had 24 people play a video game in which they attempted to follow a ‘rabbit’ with or without a flashing tail — indicated by coloured circles that blended into the background or white circles that stood out — as it made a sharp turn.

Although the ‘hunters’ were good at making the correct decision within 0.5 seconds in both cases, the presence of a ‘tail’ significantly reduced their number of correct calls. Semmann’s conclusion, presented in Newcastle, UK, at the Behaviour 2013 conference, is that there is a direct benefit to rump patches: they make a rabbit more likely to survive a hunt.