If you’ve ever tried to eat lunch in an urban park you might know this already, but ecologists have shown that squirrels get a lot more cocky when there are loads of them around. Tommy Parker of the University of Missouri-Columbia studied squirrels in several parks in Baltimore, as well as Lafayette Park in nearby Washington DC – the single place with the highest density of grey squirrels in the world. What’s more, it’s bang opposite the White House: “It’s hard to do science with all the secret service guys around,” Parker says.

The results showed that squirrels, like people, get more pushy in crowded urban areas. Parks with the highest squirrel densities witnessed more squirrel-on-squirrel brawls, and the rodents were also less nervous of people. “The Lafeyette squirrels are very aggressive and not wary at all,” says Parker. “You could walk directly up to them and they would just lean on your shoe.” Yet another reason not to loiter near the White House, then…