Incredible Journeys Exploring the Wonders of Animal Navigation

The ancient Chinese philosopher Laozi (also written Lao Tzu) supposedly wrote that “A journey of a thousand miles begins with a single step”. But as writer David Barrie shows with Incredible Journeys, before we can even take that step, every journey starts with navigation: where are you and where are you going? Animals of all stripes can make incredibly long journeys, usually without getting lost. This wonderful popular science book explores the remarkable diversity of strategies they employ to find their way.

The bulk of the book is divided over 25 short, very readable chapters in two parts: non-map and map-based navigation, with a short third concluding part containing the last two chapters. Each chapter ends with a fascinating or peculiar case study, anecdote, or passage that could not be comfortably fitted in the main story. Barrie deftly moves between summarising findings from academic papers, introducing classic studies and pioneering scientists, and first-hand reporting when he joined researchers in the field.

Humans are visual creatures and Barrie describes how both humans in the past and indigenous people today still rely on the sun and stars for navigation. Landmarks are of course other common features to use, though few people can match the perceptiveness of Inuit navigating the barren snowy landscapes of the Arctic. More unusual cues are characteristic smells and sounds, or the presence of birds near land. Barrie also goes into some of the neurobiology of human navigation, looking at the role of the brain’s hippocampus. Many more details on human navigation can be found in Wayfinding, published around the same time. And for those who want to try their hand at natural navigation, Tristan Gooley and others have turned this into a mini-genre.

Navigating the world comes with its own terminology and some helpful illustrations show earth’s magnetic field, or how the sun’s path across the sky changes during the seasons. Surprisingly though, basic terms such as azimuth and latitude-longitude are not pictured. Determining longitude, i.e. east-west position, was long a problem, even after the invention of the first navigational aids such as compasses and maps. The story of how it was cracked is told in The Illustrated Longitude and the author’s own Sextant.

The human story is just a side-show, however, because where this book really shines is its coverage of animal navigation. Barrie mentions well-known examples, such as bees and their famous waggle dance (heavily borrowing from The Dancing Bees), the ability of many insects to observe polarised light (we here meet the specialised area in insect eyes that Land also described in Eyes to See), or the migrations of the monarch butterfly (see also Chasing Monarchs). Many other mechanisms and behaviours will be unfamiliar even to most biologists and Barrie mines the primary literature for some delightful examples.

What to think of dung beetles navigating in straight lines by the faint light of the milky way? Or the ant’s in-built mental odometer which allows it to count steps (see the forthcoming Desert Navigator), the importance of smell in fish, or spiny lobsters trudging along the sea bottom in a straight line for hundreds of kilometers? Then there is the contested but increasingly well-supported idea that pigeons might be using low-frequency sound (infrasound) generated by natural processes such as wind, waves, and earthquakes. And insects, such as the Australian Bogong moth or the silver ‘Y’ moth in Europe can migrate thousands of kilometres. In closing the book, Barrie remarks that during its writing, he was struck dumb time and again by the extraordinary skills animals show while navigating. His writing instills the same in the reader, to the point that if some of these examples do not leave you in awe, you need to check you still have a pulse.

I have so far studiously avoided mentioning the two bigger topics that take up quite a bit of space in this book: bird navigation and the role of Earth’s magnetic field. Birds have been particularly well studied (see for example Long Hops or the thorough The Avian Migrant, classics such as The Migration Ecology of Birds and Bird Migration, or the very recent A Season on the Wind), and there are plenty of examples given here of the globe-spanning excursions that birds are so well-known for. Magnetoreception remains a mysterious topic so far: clearly, animals can navigate using geomagnetism, but a well-defined sense organ is not obviously present. Barrie shortly summarises the leading ideas and, as with the rest of the book, he does an admirable job distilling complex topics into clear and enthralling writing.

Animal migration is a massive topic and Barrie is upfront about only scratching the surface here. Students and practising scientists are well advised to check out textbooks such as Animal Migration and Migration: The Biology of Life on the Move. On the other side of the spectrum, the illustrations here are lovely, but if you really want to marvel at what technology has revealed, check out Where the Animals Go. But how does Barrie’s book compare to other popular science books? Notably, there is Gould & Gould’s Nature's Compass, published in 2012. It covers many of the same topics, but the authors, being biologists, provide more technical detail, no doubt better suiting readers with a background in biology. Heinrich’s The Homing Instinct is perhaps more comparable in level, but migration forms only part of his book, with “animals making a home” being the other topic covered. Incredible Journeys is thus perfect as an entry-level book for a general audience and, with its kaleidoscopic coverage of topics, is a spell-binding read.