What impels them? No one knows. Macdonald does not go so far as to suggest that they plan their journeys intelligently. But he does detect intelligence elsewhere in the animal world. Wild boar, which arrive in the orchard in December, are, he says, “hugely intelligent”. His grounds for believing this are that they eat large quantities of fruit and then excrete the seeds “complete with fertiliser”. So they play a vital role in propagating the next generation of fruit trees. It seems a desperate argument, unless you drastically redefine “intelligence”. As things stand, we seem to be the only intelligent beings, and, as Orchard vividly shows, our evolution has upset a perfectly balanced ecosystem.