THERE seems to be no limit to the resourcefulness with which insects, birds, fish and mammals navigate their way through the world.
Consider the desert ant. After meandering hundreds of metres from its nest, the ant manages to scuttle home in a straight line across unfamiliar ground. Honeybees use an internal clock and sensitivity to polarised light to remember the location of food, communicating it to their hive through their famous waggle dance. And there is the Arctic tern, taking a round trip from the north Atlantic to Antarctica of more than 70,000 kilometres.
David Barrie’s Incredible Journeys is brimful of such wayfinding wonders. But it is as valuable for what it reveals about our ignorance. No one knows how those terns stay the course across vast expanses of open ocean, nor how juvenile European cuckoos find their way to their wintering grounds in Africa for the first time without a guiding parent. Pigeons are known to have a keen sense of smell, but, despite decades of research, we can’t agree if they use it to navigate.
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The consensus is that many animals can sense Earth’s magnetic field, but how they use it remains unclear. “There are three radically different theories, any or all of which may prove to be correct,” writes Barrie, adding that “some entirely different mechanism… may be at work”.
Many biologists have spent their lives wrestling with these mysteries, and their obsessive ponderings and ingenious experiments are as fascinating as the behaviours they study. Take Rüdiger Wehner, one of the greatest authorities on the navigational abilities of ants. He made his breakthrough discovery – that they orientate using an inbuilt “sun compass”– by painting over parts of their tiny compound eyes and watching their response.
Matthias Wittlinger, intent on finding out how ants calculate distance, had the idea of attaching miniature stilts to some subjects and shortening the legs of others to see if this affected the length of their journeys. He found that his stilted ants overshot the nest while the amputees pulled up short, thus confirming his idea that they were counting their steps.
All this is enough to make anyone with the vaguest interest in science want to grab a magnifying glass and head for the desert. Thanks to the likes of Wehner, Wittlinger and Karl von Frisch (who deciphered the honeybee waggle dance), we now know a lot more about how animals get around and their acute sensitivity to their surroundings.
Barrie’s passion makes him an engaging guide, flitting from fact to anecdote like a butterfly hunting for nectar. He is no less animated about the skills of early humans, who explored most of our planet and colonised much of it “without the help of any tools, apart from their finely tuned senses and native wits”.
In the age of GPS, it is easy to forget that modern humans possess the same senses and wits, though we use them less and less. How our brains form the cognitive maps that allow us to remember routes and places is as mysterious – and in many ways as remarkable – as the migration of the Arctic tern or the dead reckoning of the desert ant.
Let’s hope that by the time spatial neuroscience has revealed more about our wayfinding faculties, we still know how to use them.
Hodder & Stoughton
