Sicily has a four-legged early warning system for Mount Etna. It has a beard, it eats gorse, and it is beating several million euros of monitoring equipment by half a day. The shepherds have known this for as long as anyone has kept goats on that mountain. The herd tells you. No drama about it, no bleating, no rearing up and pointing at the summit. They simply decline to go up the hill that morning, and if the goats will not go up, neither do you. Oldest volcano warning system in Europe. Costs nothing. Runs on scrub. For most of history the scientific response to this has been a polite nod and a change of subject. Then in 2011 a German turned up with a box of trackers. Martin Wikelski of the Max Planck Institute of Animal Behaviour has an unfashionable habit of asking local people what they already know before deciding they are simple. He collared goats living year-round on the slopes and started logging where they went, and when, and how fast. On 4 January 2012 the data went peculiar. The animals turned down the high pastures they use every day of their lives, all of them, and headed for the trees. The seismometers were quiet. The gas monitors were quiet. In a control room in Catania, a great deal of very expensive equipment was reporting a perfectly ordinary Wednesday. That evening Etna started throwing lava and ash into the sky. Six hours. The same signature has now turned up before eight major eruptions, and at the extreme the goats move fourteen hours ahead of the mountain. Ahead of the tremor. Ahead of the gas. Ahead of everything the volcanologists are paid to watch. Nobody knows how they do it. The best guess is sulphur dioxide and hydrogen sulphide venting beforehand at concentrations no human nose could ever find, which would mean the animals are smelling the future and declining to comment. Wikelski's own summary is that they know in advance, we have no idea how, but they do. The institute says there is not yet enough data for a formal warning system. More eruptions, more animals, more species. Which is the correct scientific answer and a very funny one, since the shepherds reached sufficient confidence somewhere around the Bronze Age and have been acting on it every day since. Rome had geese who saved the city by making a racket when the Gauls came over the wall, and honoured them for it every year afterwards. Etna has their spiritual successors, doing the same job by refusing to walk uphill. We have a word in English for a man who behaves like a goat. It means he eats anything, wrecks anything, and understands nothing. The goat currently outperforms a seismograph.