Animals that live in the city are usually less wary of humans than their rural counterparts. Most people think the boldness comes from experience: since the majority of humans are rather harmless, the critters learn to go about their business without fear. But the truth turns out to be far more interesting, at least for Australian swans. Turns out the city birds are genetically different from their country counterparts. Australian researchers looked at two groups of swans. One population lived on a pond in the center of Melbourne. The second hung out just 30 kilometers away in a more bucolic setting, surrounded by far fewer humans. The researchers measured what they call each bird's "flight initiation distance": basically, how close could a human get before the swan would just fly away? "We found that the flight initiation distance for the swans at the urban environment was only 13 meters, and on average at the non-urban environment it was 96 meters. So that's like an 83 meter difference, a really big difference in how wary these swans are at the two habitats.