53. An introduction to the science of animal navigation

I recently enjoyed giving an online talk for students at the University of Kentucky. You might find it interesting if you want a very quick introduction to this fascinating subject!

48. How can creatures without brains remember where things are?

You might well suppose that the ability to keep track of where things are depends on having a brain of some kind - or at least a nervous system

But you would be wrong. Not only can single-celled organisms find their way towards things they need (like food) and away from things they don’t like (such as too much heat), but some of them can also remember locations. This is of course a key navigational task.

One fascinating class of single-called critters - with the unappetising name of slime moulds - has long been known for its ability to build highly efficient transport networks. As I mentioned in Incredible Journeys/Supernavigators, these giant, unicellular organisms can even solve a problem that has taxed the brains of human engineers: how to create the most efficient rail network connecting a number of cities and towns of different sizes.

Until now it has not been entirely clear how slime moulds achieve these feats. But a new study reveals how these apparently simple organisms can ‘remember’ the things that most matter to them.

Slime moulds are in the business of building tubes for moving nutrients around (just as railroads are used for moving people or goods). It seems that they respond to the presence of food by expanding the diameter of the tubes they build. The richer the source, the bigger the tube leading to it. Information about nutrient locations is therefore encoded directly in the physical structure of the tube network. It is a kind of associative memory.

As the researchers put it, ‘nutrient location is stored in and retrieved from the networks’ tube diameter hierarchy’. Their findings help to explain ‘how network-forming organisms like slime molds and fungi thrive in complex environments’. Since slime moulds and fungi are now known to perform a wealth of vital tasks, this is an important discovery.
What’s more, it may prove helpful to human network designers.

45. How to make electronic navigation more engaging - and rewarding

Many navigators are worried about the consequences of our increasing reliance on automatic navigation systems - especially the ‘turn-by-turn’ apps based on GPS that are now embedded in every cell phone and every vehicle.

There’s plenty of evidence (which I discuss in Incredible Journeys/Supernavigators) that the passive use of these apps impedes the development of the mental maps that enable us to find our way around most efficiently.

There are even those who think that we may endanger our overall cognitive health by using them too much. And there’s no doubt that these apps impoverish our lives by discouraging us from taking an active interest in the world around us.

But nobody seriously thinks we can turn the clock back. Navigational apps are here to stay because they make life so much easier - and sometimes (though not always) safer.

The question is whether they can be tweaked so as to reduce or eliminate some of their drawbacks.

An interesting new study (Clemenson, G.D., Maselli, A., Fiannaca, A.J. et al. Rethinking GPS navigation: creating cognitive maps through auditory clues. Sci Rep 11, 7764 (2021). https://doi.org/10.1038/s41598-021-87148-4) examines the virtues of a different kind of app - one that does seem to help people develop a better grasp of the layout of their surroundings.

Instead of relying on the usual turn-by-turn directions, some participants in the new study followed a virtual, auditory compass (based on the Soundscape app - originally designed for visually-impaired users) in order to locate various goals dotted around the Microsoft campus. The compass indicated the straight-line route to each goal, and the user then had to navigate actively around any obstacles (like buildings) that stood in the way.

The authors acknowledge that the sample size was small, but they insist that - in contrast to a standard turn-by-turn app - the Soundscape virtual compass helped participants who were new to the campus develop a better sense of its geography.

They argue that “using auditory beacons to navigate can lead to greater explorative behavior and the formation of more accurate mental maps of the surrounding environment when compared to turn-by-turn navigation. Thus, demonstrating that it is possible to use GPS technology and promote learning through active navigation.”

They conclude that an auditory beacon is “a sensory augmentation that helps us create a stronger connection with our environment.”

This is a promising development, and I hope we’ll soon see more research of this kind. But I wonder whether the mass market navigational platforms will take heed of the new findings - and whether users are ready to embrace a more active approach to navigation than they have got used to. We’ll have to wait and see.

31.Joshua Slocum on the joys of celestial navigation

One of the things that bothers me about our ever-increasing reliance on technology is the way it distances us from the natural world.  Yes, yes – it makes life easier in all sorts of ways and it would make no sense to turn our backs on it, but all that convenience does come at a cost.

This is especially true of GPS.  Have you ever had had the slightly weird experience of allowing the in-car ‘satnav’ to lead you astray on a journey to a place you knew perfectly well how to find?  We’re so beguiled by its extraordinary accuracy and reliability that we daren’t challenge its authority.  GPS can be disabling – reducing us to a state of child-like dependence and making us behave like complete idiots.  In fact it actually weakens our ability to navigate naturally, as recent research has confirmed (see earlier post).

The Inuit peoples of Northern Canada worry that young people who have become reliant on GPS can’t safely find their way around in the Arctic wilderness and easily get lost – which is no joke up there.  Their elders, by contrast, just using natural cues like the sun and stars, landmarks of all kinds, the wind, the shapes of snow drifts, and the behaviour of the wildlife, can find their way in almost any weather.  Apparently they never get lost even if they sometimes have sit tight for a while when there’s a complete ‘white out’.

Over the last 20 years GPS has come to dominate marine navigation almost completely.  Integrated electronic navigation systems based on GPS are now installed even on small boats.  Basically they offer a ‘moving map’ display on which the vessel is represented by a little boat-shaped icon.  

Linked to the GPS – and maybe also to radar and other instruments – these ‘Electronic Chart Display and Information Systems’ (ECDIS) have taken all the hard work out of navigation.  With a click of a mouse you can find out how far you have to go to reach your destination, what the best course is, how long it’ll take to get there, how much current is against you and much else besides.  

It’s quite brilliant but it’s also totally infantilising.  You’re turned into a mere consumer of navigational information with no part at all in the complex business of generating it.  A glance at the display tells you exactly where you are – and  you don’t even have to raise your head to look at the world outside.

Maybe that’s fair enough if you’re a professional seaman who just needs to get safely from A to B by the fastest route, but there’s something a bit sad about recreational sailors relying on GPS and ECDIS – as they increasingly do.  After all, what’s the point of going sailing, if not to be experience the wonders of the natural world?   (I leave aside the point that exclusive reliance on electronic navigation aids is actually very risky - a subject I might come back to one of these days.)

The sea is the last great wilderness and there are few things more rewarding than to find your way across it with a sextant in your hand.  To fix your position in mid-ocean by taking sights of unimaginably distant stars is a truly sublime experience.  

As the first single-handed round-the-world yachtsman, Joshua Slocum (1844-1908), said after finding the Marquesa Islands just where he expected (using the old lunar distance method for finding longitude):

To cross the Pacific Ocean … brings you for many days close to nature, and you realize the vastness of the sea. Slowly but surely the mark of my little ship’s course on the track-chart reached out on the ocean and across it, while at her utmost speed she marked with her keel still slowly the sea that carried her. On the forty-third day from land,… the sky being beautifully clear and the moon being ‘in distance’ with the sun, I threw up my sextant for sights. I found from the result of three observations, … that her longitude by observation agreed within five miles of that by dead-reckoning.

29.Bats with maps?

Bats suffer from big PR problems. They are traditionally associated with all kinds of bad things - from vampires and the devil, to rabies and COVID-19. And many people think they’re ugly too, though I think this Egyptian fruit bat is actually very cute.

But one thing is beyond doubt: bats are very clever.

Many of them fly by night and have astonishing powers of echolocation, while others are day-flyers that rely on their excellent eyesight. Some bats migrate over large distances. And they’re all very good at navigation.

A new study from Lee Harten et al. at Tel Aviv University sheds light on the Egyptian fruit bat’s impressive navigational skills - and in particular, whether they make use of a ‘cognitive map’.

As I explain in Incredible Journeys, the cognitive map has been the Holy Grail of animal navigation studies ever since it was first proposed back in the 1940s by the great Berkeley psychologist, Edward Tolman.

Because rats sometimes use shortcuts when searching for food rewards in mazes - entirely novel routes that they have never used before - Tolman thought they might be making use some of some kind of ‘cognitive map’ on which they stored information about the layout of their surroundings.

This was a very controversial idea because rats were then thought capable only of learning fixed routes based on trial-and-error (otherwise known as ‘stimulus-response’ or ‘S-R’ learning). Acquiring map-like knowledge couldn’t easily be explained in S-R terms, so it seemed impossible - according to the prevailing behaviourist orthodoxy.

Tolman was attacked on all sides and his opponents came up with all sorts of alternative explanations for the behaviour of the rats - some of which were pretty bizarre. But when cognitive neuroscience took off in the 1960s, it became possible to monitor what was going on in the brains of living experimental animals. And many discoveries made since the 1970s have born out Tolman’s hypothesis.

To cut a long and complicated story short, there’s now abundant evidence that various mammals - including rats, mice and human beings - have brain circuitry that allows them to form cognitive maps of their surroundings, though there’s still plenty of room for debate about how these work in practice.

What is less clear is whether any other animals have the same abilities, though there are some scientists who would make that claim - even for insects like honey bees.

Bats of course are mammals and it would be quite surprising if they were any less gifted navigationally than, say, rats or mice. After all, they navigate over much larger distances - and they are obliged to do so in three dimensions!

The new study is interesting because it provides pretty solid evidence for the first time that fruit bats really do use cognitive maps.

Using GPS trackers, Harten et al. mapped every single journey taken by 22 young bats (‘pups’) starting with their first excursion outside the nest and continuing every night thereafter for five months.

The pups gradually extended their home ranges until these reached a mean area of about 60 square km. Sometimes they undertook exploratory flights which took them beyond into unfamiliar territory. When they detected new sources of food, they would return to them later on to feed.

The striking finding was that the pups - like Tolman’s rats - often performed impressive shortcuts. These were defined as routes in which at least 50% of the animal’s journey was novel (i.e. the pup passed no closer th100m to any location it had previously visited).

You may wonder whether these shortcuts were just chance events. Well, they certainly looked intentional.

The paths the pups followed were almost as straight as their regular ‘commuting’ routes to familiar sources of food, and they were much straighter than their exploratory flights. Moreover, the pups headed straight for their targets right from the outset of these flights. Some of the lengthier shortcuts (described by the researchers as ‘long-cuts’) occurred at the end of exploratory flights. These sometimes involved navigating for many kilometers over unfamiliar territory.

And out of the 246 short- and long-cuts that were observed, hardly any was predictable on the basis of a randomised (‘random-walk’) movement strategy.

Could the pups have been following a scent trail?

There is plenty of evidence that homing pigeons make use of olfactory cues to find their way back to their roosts - especially when taken to distant and unfamiliar locations (though this is still the subject of some debate). But Harten et al. found no correlation between wind direction and navigational straightness. On this basis they judged it unlikely that the bats were relying on olfaction, though they could not rule it out completely.

What about echolocation then?

The researchers note that the bats’ echolocation system has quite a limited range - for example, they can detect a large tree only when it is within 50 m.

Harten et al. also found no evidence that the bats were making the kind of errors that would be expected if they were relying on ‘path integration’ or DR to make their shortcuts.

So they concluded that the bats must have been relying primarily on their acute vision to perform these navigational feats.

But of course good eyesight alone isn’t enough.

Harten et al. believe that, before setting off, the bats look around them and use the spatial arrangements of distant landmarks (such as high-rise buildings) to judge where they are and the heading they need to follow to reach their goal.

And since the bats are not following the same routes again and again, they must have some way of storing the different locations of these landmarks (as well as their varied appearances) in a form that doesn’t depend on any fixed point of view.

So, it really does look as if they must have some kind of cognitive map, though it will be interesting to see how other experts react to the new study.

21.Mother and father goose lead the way…

You’ve probably seen geese flying in a tight V-formation, and you may have wondered why.

It seems that the upwash from the wings of the lead bird gives a bit of extra a lift to the birds following on either side, and thus reduces their energy consumption - an effect that continues down the line to the tails of the V. That really matters on a long migratory journey, but the lead bird obviously has to work a bit harder than the rest. So it came as no surprise when some recent studies showed that birds took turns in taking the lead, thus sharing the extra burden.

But something slightly different emerged from a fascinating new study.

Researchers attached lightweight GPS trackers and accelerometers to wild white-fronted geese belonging to four family groups setting out on their long migration from the Netherlands to northern Russia. This meant that they could not only see exactly where each bird was in the formation, but also how fast they were flapping their wings.

It turned out that only the parents ever took the lead. Usually the father, but sometimes the mother - depending on the wind conditions. The mothers had to flap their wings faster when they were out in front, but the fathers apparently did not need to.

It makes good sense for the parents to take on this leadership role, because it increases the chances of their offspring surviving the rigours of the long journey - and thus having a chance to pass on their genes to future generations (so-called ‘kin selection’).

But this system probably also helps the young, first-time migrants to learn the route they need to follow in future, where best to stop for refuelling, how best to avoid dangers - and indeed how to fly most efficiently.

In groups of homing pigeons, less experienced birds follow more experienced flock members, and this helps them to learn routes. Further experiments will be needed to see whether this is also true of young migratory geese.

19.Young cuckoos are even cleverer than we thought…

A couple of weeks ago I wrote about the amazing journeys undertaken by adult Mongolian cuckoos - like Onon in this picture.

Here I talk very briefly about a fascinating new study, just published in the journal Nature. It reveals that young cuckoos - making their very first migratory journey all the way from Russia to Southern Africa - can somehow tell when they have been moved 1800 km to the east of their proper route. And, just like experienced adult birds, they can change course to compensate for this displacement.

It’s the first time such an ability has been clearly demonstrated in young birds and it leaves us wondering how they solve a problem that we humans only cracked a few hundred years ago.

18.My interview for the Stratford Literary Festival

I was lucky to be interviewed by the novelist Clare Clark who asked extremely good questions. I hope my answers measured up to them!

17.Amazing cuckoos

There’s no better way of getting a sense of what migratory birds can do than to look at the maps that record their journeys.

The Mongolian Cuckoo Project has been using tracking devices to follow the amazing journeys of cuckoos returning home from Southern Africa in recent weeks. Do please visit their excellent website to see the achievements of Onon, Bayan and the other birds. It’s a real model of public engagement in science.

Quite apart from the extraordinary distances the birds have been covering, I’m struck by the close similarity between the routes they have been following. It would be fascinating to know exactly how they perform such impressive navigational feats.

Presumably, like many other migratory birds, cuckoos have a sun and star compass as well as a magnetic one. And when they have made their first migratory journey, it’s safe to assume that they use familiar landmarks to help them retrace their route. But of course there are no landmarks over the ocean!

And cuckoos face a special problem. Their unusual lifestyle means that when they first head south, they must do so alone - because their parents will have left before them.

So how on earth do they find their lonely way over thousands of miles of land and ocean to the areas in Africa where they pass the winter months? Some kind of genetic program must be involved. But how does that work? We just don’t know.

One last thing: why not lend your support to this brilliant project by following this link?

15.How do dogs find their way home?

Dogs seem to have a built-in magnetic compass…

13.How birds steer by the light of the stars...

Polaris (aka the Pole Star) stands in the sky vertically above the North Pole (not quite exactly, but near enough). That means that if you were at the North Pole during the long Arctic night and looked directly overhead you’d see Polaris. And if you were anywhere else in the northern hemisphere, facing towards Polaris, you would be looking due north (true, not magnetic). Though, as I explain in the video, thanks to the phenomenon of ‘precession’, this would not always have been the case, nor will it be in the not-too-distant future.

If you know where true north is, you can set a course in any direction. No wonder Polaris used to be called ‘Stella Maris’ - or the ‘star of the sea’. In the Middle Ages, the same term (which can also be translated as ‘the star of Mary’) was applied to the Virgin Mary, whose sky-blue cloak is emblazoned with a star in many medieval paintings. Mary was likened by the theologian Alexander Neckham (1157-1217) to the Pole Star, standing at ‘the fixed hinge of the turning sky’ by which the sailor at night directs his course. As I wrote in SEXTANT, ‘Polaris must have seemed a perfect symbol for the Mother of God, the immaculate spiritual guide and intercessor’.

https://upload.wikimedia.org/wikipedia/commons/5/5a/Star_Trails_Shoreline.jpg

But, as I explain in this video, birds are not human and they don’t use Polaris. Instead, they wisely attend to the rotational pattern of stars around it - something on which they can always count. To illustrate this, here’s a long-exposure photograph of the northern sky in which you can see the circular paths traced by each star. Polaris itself appears as a stationary dot at the centre of the pattern. The same principle would also work in the Southern Hemisphere, which is handy because there is no southern equivalent of Polaris: the southern celestial pole lies in a rather blank patch of sky, at least for the present!

12.The amazing journey of the blackpoll warbler...

Here is the first of what, if I have the energy, will be a series of short videos introducing some fascinating aspects of animal navigation. It relates to a tiny American bird: the blackpoll warbler.

These birds normally only weigh about 12 g and even when they fatten themselves up for their long migratory journey they only put on another 5 g. I think you’ll be as amazed as I was to discover what they can do.

The original research on which this story is based can be found here: DeLuca, W. V., Woodworth, B. K., Rimmer, C. C., Marra, P. P., Taylor, P. D., McFarland, K. P., ... & Norris, D. R. (2015). Transoceanic migration by a 12 g songbird. Biology letters, 11(4), 20141045.

11.Francis Chichester learns to navigate...

Sir Francis Chichester (1901-1972), best known today for his solo single-handed voyage around the world in the yacht Gipsy Moth IV, first learned to navigate in the air. In fact, he was a pioneering aviator (the first to fly solo across the Tasman Sea from east to west) and he only took to sailing towards the end of his career.

Chichester was to become an expert navigator, but, like the rest of us, he had to learn. Here’s his entertaining account of how, in 1929, he flew a Gipsy Moth aircraft from Liverpool to North Devon, not long after he had acquired his solo license (‘Bradshaw’, I should explain, was the standard railway handbook of the day):

The aeroplane was so knew that it had not yet been fitted with a compass. I was ‘flying by Bradshaw’, following the railway lines across the country, and I wondered if I could fly by the sun. The sky was overcast…I climbed up into the cloud, and proceeded until I had passed through a 9,000-feet layer of it to emerge at 10,000 feet in brilliant sunshine over a snowy-white field of cloud. Not only had I no compass, but no blind flying instruments at all…After flying along for half an hour by the sun, I climbed down through the 9,000-feet layer of cloud. I then wanted to find out how accurately I had carried out this manoeuvre, and I used a sound principle of navigation. I fixed my position by the easiest method available – I flew round a railway station low down, and read the name off the platform. By some extraordinary fluke I was right on course. I probably uttered for the first time the navigator’s famous cry ‘Spot on!’

From The Lonely Sea and Sky, Chapter 7. (Hodder and Stoughton, 1964)

10.Barry Lopez on polar bear navigation

In his classic work, Arctic Dreams, Barry Lopez occasionally refers to the remarkable navigational abilities displayed by animals of the far north. Polar bears for example:

“ Bears make use of mountain passes, ravines, and other features of the land in such a way as to suggest that these are traditional routes…

” Beyond using celestial clues and a knowledge of prevailing winds and currents, which reliably guide Eskimos across the angular topography of shifting sea ice, no one knows how bears find their way. But they consistently travel directly to aggregations of seals; they return to core denning and breeding areas every year; and they find their way unerringly to the coast from hundreds of miles offshore. This would be astonishing enough if they only did it on land, where there are perennial landmarks, but they also do it at sea, where a frozen landscape is created anew each year, which can change from one day to the next… In some areas of stable ice, bears may travel for weeks without seeing a break in the continuity of the sharp blue line of the horizon…” [from Chapter 3, Tôrnâssuk.]

Maybe, as Lopez suggests, the bears do indeed use celestial cues, like the azimuth of the sun. Maybe they also know about prevailing winds or currents. It’s equally possible that they use their acute sense of smell. Lopez also speculates that the bears make use of maps in their heads - or cognitive maps - but I’m not sure the evidence really supports such a claim. Perhaps they are just good at DR? In any case, the secrets of polar bear navigation are one more mystery to add to my growing personal list of puzzles!

8. a video introducing ‘Incredible Journeys’ (‘Supernavigators’ in North America)

This is a 15-minute version of a video I made recently as an introduction to some of the main themes of the book. I hope you enjoy it!