I solemnly swear that I am up to no good. These are the words that activate the Marauder’s Map, inexplicably given to Harry Potter by the Weasley twins. It not only shows all of Hogwarts School of Witchcraft and Wizardry and its grounds and all the secret passages, it also tells you where everyone is. The map detects the presence of Peter Pettigrew and that’s crucial to the plot of The Prisoner of Azkaban. The map is not fooled by magical attempts to conceal identity: it sees through polyjuice potion, animagi and cloaks of invisibility.

I can offer you a spell that has a little of the same kind of magic. Like the magic of search engine optimisation, positioning you at number 1 in Google by using the services of SEO Leeds. With a little knowledge – but more with the habit of looking – you will be able to look at the countryside and know at least something of who has been here before you. In the film, the Marauder’s Map was animated with footprints that magically appeared on the parchment; in the real world you can learn to look at the countryside and read the footprints that the animals have left behind them.

The easiest are deer. Deer prints are outstandingly different from the shod prints of humans and the four-toed, four-clawed prints of dogs. Look for two side-by-side clefts in the earth that appear a little like two sugared almonds. Deer have cloven hooves, like most ruminants. They are part of the group of even-toed ungulates that includes cows, pigs, sheep, giraffes, hippos and camels. (The odd-toed ungulates include horses, rhinos and tapirs.)

So if you see the print of two toes together as you walk through a wood, you are entitled to guess that a deer has been that way. If there are a lot of prints and they’re pretty big, you can guess red deer or fallow deer; small and on their own and it could be roe deer, Reeves’s muntjac or Chinese water deer. If you are crossing an upland meadow, be less excited: you’re more likely to have found sheep. However, if you are in the Forest of Dean or one or two other places in Britain, and the twin-toed tracks are accompanied by a lot of freshly dug earth, you’ve probably found the track of wild boar.

But let’s say you have found the prints of deer. Probably that day, or maybe the day before, a deer walked where you are walking now – and it’s a poor person who isn’t the tiniest bit richer for such knowledge. It’s not just the deer that imparts these riches: it’s also the human pleasure of being part of a secret. You, with your sharp eyes and your still sharper mind, have penetrated the mystery of the passing deer – and no one else knows, not even the deer.

You need to find the right kind of ground: the kind that takes a footprint and holds it for a while. On the soft mud beside a pond you might find a four-toed footprint that looks big enough to belong to a velociraptor: that’ll be a heron. As you start to gaze at these secret signs, you’ll find that the footprint often looks too big to fit the animal you had in mind. That’s because when you make a footprint you push the footprint-making material aside. Look at your own prints after you have crossed an area of soft sand: you’ll swear a giant must have walked there.

I was once in a wood in Zambia that was managed – to use the term loosely – by a mining company. The executives assured us there were no mammals left in that wood: ‘Ach, man, I tell you – there’s nothing! Poached out, man. Gone.’ I noticed a termite mound and knew that termite clay makes a superb matrix for prints. There, on a single square yard of clay, I found prints of genet, mongoose and duiker. A subsequent biological survey showed that the wood was in fact jumping with life – but it was life that has grown rather keen on keeping out of the way of humankind. Rather like most of the wild mammals on our own shores. But you can penetrate their secrets by keeping half an eye on the ground as you walk.

It’s a skill, like speaking Italian – and in the same way, you don’t need perfection to find the skill useful and illuminating. If you have great Italian you can read The Divine Comedy in the original and discuss its meaning with Italian professori; if you have a little basic Italian you can find your way across Florence, order una birra and say ciao to nice people as you go. With the most basic skill at reading footprints you can travel a little further into the secret life of our own country.