30.Darkness matters much more than you might think...

We’re only just starting to realise that our love affair with artificial light at night (ALAN) is bad not just for us, but also for many of the creatures with which we share this planet. Including, for example, the sandhopper.

But before I talk about the problems facing this remarkable crustacean, let me sketch in a bit of background about light pollution.

Paris was the first European city to introduce street lighting. That was in 1667, during the reign of Louis XIV - The Sun King. Very soon other major cities across Europe followed suit. (I’m not sure about Asia - I suspect that Edo was pretty well lit too and maybe even earlier than Paris. Does anyone know?)

Streetlights in those days were pretty dim - just candles or oil lamps. While they made nocturnal city life easier and perhaps a bit safer, they didn’t have much effect on the visibility of the night sky. In the countryside, the nights remained as dark as they had always been.

Things changed with the arrival of gas and electric lights in the 19th century. Cities could now be brilliantly illuminated. More light seemed to be an unqualified good, and few resisted its encroachments. Today of course we have many other kinds of lighting - like LEDs and fluorescent tubes.

ALAN is spreading rapidly across the face of the earth.  Everywhere you go, there are brilliantly lit office buildings, factories, airports, docks, military installations, car parks, apartment blocks and even private houses.

But ALAN is not restricted to built-up areas - it extends outwards along the roads that connect the cities and towns where we live. You can’t even escape it completely on the open ocean, where oil rigs, ships and fishing boats are often lit up like Christmas trees.

The problem is not just the direct glare of the lights themselves.

There is also the phenomenon of ‘skyglow’ caused by the scattering of light from clouds and dust in the atmosphere.

One of the sad consequences of ALAN is that most people on earth can no longer enjoy the wonder of a dark night sky with its thousands of stars - and they will never see the Milky Way.

Big cities generate so much light that the skyglow above them can sometimes be detected a hundred miles away or more. It is the most widespread form of light pollution and apparently now affects 23% of the earth’s surface between the latitudes of 75 degrees North and 60 degrees South. That includes many of the most important areas of biodiversity around the world. And it continues to spread rapidly.

Of all the many serious environmental problems we face, ALAN is actually the easiest to solve.

Better designed lights, properly shielded, pointing in the right direction, and only as bright as they need to be, would make a huge difference. Steps like these would not be expensive to implement. They would also save energy and reduce costs in the long run. (For more information about light pollution and how to combat it, visit the excellent website of the International Dark-Sky Association.)

In recent years scientists have begun to pay attention to the effects of ALAN, both on us humans and on other animals, as well as plants.

ALAN certainly has a disruptive effect on the internal clocks that govern many natural processes - including our own sleeping patterns.

It is a well-known menace to turtle hatchlings, as well as migratory birds. It may also be implicated in the decline of many insect species.

And now it looks as if ALAN is also making life difficult for the poor little sandhopper.

These animals live on sandy beaches and, as I explained in Incredible Journeys (Chapter 10), they are remarkable navigators.

In the evening they make their way to water’s edge to chomp on seaweed. In the morning they retreat up the beach and bury themselves in the damp sand to avoid getting dried out by the sun. Since they can easily get drowned, it’s important that they don’t go the wrong way.

Amazingly, sandhoppers have not one but two celestial compass systems that help them steer in the right direction - whether up or down the beach. One is based on the light of the moon and the other on the sun.

A new study (unfortunately locked behind a paywall) from D. Torres et al. looks at how skyglow affects the navigational ability of sandhoppers on the coast of the island of Anglesea, Wales.

They report that skyglow - though much weaker than direct light pollution - nevertheless disrupts the sandhoppers’ lunar compass system, making it harder for them to navigate safely at night.

Since many other animals use the stars and the moon to help them orient at night, it is a sure bet that ALAN is not just causing trouble for sandhoppers.

Torres et al. conclude that ‘a renewed focus on the ecological impacts of artificial skyglow is urgently needed’ in order to understand how it is affecting the world around us.

Yes indeed.

And in the meantime, please do think about how you can reduce your own light footprint!

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.

28.Green turtles aren’t perfect navigators - but they don’t have to be

Charles Darwin was one of the first scientists to speculate about how sea turtles navigate on the open ocean. It’s a fascinating question and two whole chapters of Incredible Journeys are devoted to it.

One of the experts I interviewed was Paolo Luschi whom I visited at the University of Pisa. Paolo has spent many years doing experiments on turtles in the field, and he warned me to be sceptical of claims that these animals - remarkable though they are - are brilliant navigators.

A fascinating new piece of research reinforces his point.

Graeme Hays and his colleagues (including Paolo) tracked 33 green turtles migrating from their nesting beaches on the remote Indian Ocean island of Diego Garcia to their habitual feeding grounds dotted around the western part of that vast expanse of sea. The turtles travelled anything from a few tens of kilometers to more than 4,000.

Several interesting things emerge from the analysis of their data.

Firstly, the animals very seldom went directly to their destination - sometimes they massively overshot and they often strayed wildly off track. Nevertheless, they were still able eventually to locate their targets.

Secondly, the turtles were mostly swimming in such deep water that they had no chance of seeing the seafloor beneath them (they don’t normally dive deeper than 50m). In these circumstances it would be hard for them to make use of underwater topography to guide them. However, when they got close to their destinations and entered shallower water, they were able to head fairly directly towards them. This suggests that they were making use of ‘landmark’ information - possibly acquired on previous trips.

This study also compared what the real turtles did with what they might have done based two different assumptions about how they navigate.

The first, stringent assumption was that the turtles are true ‘map and compass’ navigators - able, that is, both to work out where they currently are and where they need to go to reach their goal.

The second, much simpler one was that the turtles only had access to a compass of some kind that would enable them to maintain a steady course. This would of course give them no positional information.

When the actual tracks followed by the turtles were compared with the ‘virtual tracks’ that emerged from the simulations, it became clear that the turtles were not perfect map and compass navigators. They lacked ‘the ability to always locate small isolated targets with pinpoint accuracy’.

But, since they were still able to find their targets, it looks as if the turtles must have access to some kind of ‘map’, though plainly not a very detailed or precise one.

Such a map is very likely to involve geomagnetic cues, though other factors might also be involved. (Ken Lohmann’s studies of captive loggerhead turtle hatchlings have already shown their acute sensitivity to geomagnetic information - see Incredible Journeys chapter 22 for a summary.)

It’s also clear that the turtles don’t rely on following a single, fixed compass course. This makes very good sense as such a crude mechanism would make them vulnerable to the disturbing effects of ocean currents that deflected them from their proper course..

The researchers found no evidence that, in the final stages of their journeys, turtles were making use of olfactory information - either smells in the air or tastes in the water - carried to them from their target. This is quite surprising, especially as hints of such an ability have emerged from earlier research.

This new study illustrates an important principle. Evolution doesn’t favour the emergence of perfect systems of navigation (or anything else), when merely adequate ones will enable animals to survive and reproduce successfully.

Good enough is good enough!

26.New light on whale navigation

Dogs may be interesting, but whales are really fascinating!

In Incredible Journeys I wrote about the mysteries that surround the extraordinary navigational feats of humpback whales.

And I mentioned the possibility that whales might be making use of gravitational information.

How could that possibly work?

Well, roughly speaking, the idea is that these huge beasts may be able to track changes in their buoyancy resulting from alterations in the gravitational forces to which they are subject.

These changes may result from anomalies in the bedrock beneath the ocean, changes in latitude, or astronomical influences - like tidal forces and the varying distance between the earth and moon.

An ability to detect gravitational patterns in the submarine landscape would obviously be navigationally useful. And if the whales are also aware of changes in the earth-moon gravitational system, those could perhaps help them time the start of their migratory journeys.

Now some new research from Travis Horton and his colleagues has shed more light on these intriguing ideas.

Horton and his team have been sifting evidence about the migratory behaviour of humpbacks travelling between their calving grounds on the Abrolhos Bank (in the tropical seas off the coast of Brazil) and their feeding grounds far to the south, in the chilly waters of the South Georgia Basin.

The data come from old Soviet-era records of whale-hunting activities (bizarrely hidden for many years in a potato cellar!), and more recent satellite-based tracking studies.

These records, which stretch back 50 years or more, show that the whales have continued faithfully to follow the same migratory ‘corridor’ - despite the fact that the relevant geomagnetic and oceanographic conditions (eg currents and food availability) have varied greatly over that period.

As Horton et al. put it, ‘humpback whale migrations do not change in a changing ocean’.

After carefully analysing the tracking data, the team conclude that the whales follow ‘richly patterned and highly reproducible trajectories’. Moreover, these trajectories do indeed appear to reflect the varying gravitational forces to which the animals are subject.

They also found that the tracked whales fell roughly into two groups: those that tended to travel relatively fast and those that travelled at a more sedate pace.

Interestingly, eight of the nine ‘slow’ whales started their southbound migrations just before or during the first or last quarter of the moon. By contrast, eleven ‘fast’ whales head south near the full or new moon. Curiously, the whales that ‘sang’ swam more slowly than the non-singing ones. I wonder why?

While lending weight to the theory that the whales make use of gravitational information, this research certainly doesn’t rule out the possibility that the whales also make use of geomagnetic information - as several earlier studies have proposed. It does however suggest that they don’t rely exclusively on magnetic cues. And this would certainly make good sense if, as in this case, those cues are constantly changing.

25.How hunting dogs find their way ‘home’ in a forest

Here’s a link to a fascinating recent piece of research that explores the homing abilities of hunting dogs with a very well-developed sense of smell - so-called ‘scent hounds’.

Katerina Benediktova and her colleagues put ‘action cams’ and GPS-tracking collars on 27 hunting dogs and let them roam freely around a forest. (NB: the dogs were not passively moved to a new location like the animals in the earlier experiments we’ve considered.) They then analysed how the dogs found their way back to their owners - across no fewer than 622 trials at 62 locations.

(Even if you don’t want to get into all the details, it’s worth watching this video clip - it’s really fun!)

The team predicted that the dogs would either follow their own scent trail back to their owner (‘tracking’) or they would take shortcuts - a strategy they called ‘scouting’.

And that’s exactly what they found.

In 399 cases (almost 60%) the dogs used a simple tracking strategy to retrace their outward route. But in 223 cases (33%) they homed by a novel route. Somehow they ‘scouted’ out a completely new path that would take them back to their owners more quickly and directly.

How did they do that?

The research team have pretty well ruled out the possibility that the dogs made use either of the sun or polarisation patterns in the sky to help them set a course. They also believe that the wind direction would in most cases have made it very difficult for the dogs to ‘scout’ their way back to their owners using only their acute sense of smell.

But they did discover something quite new.

The ‘scouting’ dogs typically performed a short north/south run just before setting off for home - a so-called ‘compass run’.

Benediktova and her team think that these ‘compass runs’ reflect the dogs’ ability to detect the Earth’s magnetic field. They suggest that the runs may help the dogs’ recalibrate their DR (or ‘path integration’ system). In other words, they may help the dogs eliminate errors that have accumulated in their estimates of their position relative to their starting points. So perhaps their homing system is based on DR.

While this might explain how the hunting dogs in this experiment homed successfully, it’s hard to see how the dogs in the earlier experiments could have used DR to find their way home after being passively displaced. How would a dog in a closed basket accurately keep track of its position after a circuitous journey to a location 89 km away?

While it now looks more likely than ever that a magnetic compass plays an important part in the amazing homing abilities of dogs, I wonder whether they also make use of some kind of ‘cognitive map’ that works in conjunction with their DR, olfactory and compass skills.

More research is needed to tease out these issues.

No doubt there’ll soon be more to say on this subject. I’ll try to keep you posted!

24.How guide dogs navigate…

In my last two posts I’ve mentioned the intriguing evidence that some kind of magnetic compass is involved in the remarkable homing abilities of dogs.

But a compass by itself only tells you which way you’re facing. It can’t tell you which way you should go - unless you already know the direction you need to take.

So how could a dog that wants to find its way home know which way to go ?

The most obvious possibility is that, like many other animals, dogs are good at DR (or ‘path integration’).

DR (as I’ve discussed in earlier posts) is the process of keeping track of your position by recording each and every course change as well as the distance covered between each one. By ‘integrating’ this information you can in principle set a course that will take you directly home.

An innovative recent experiment explored the navigational capabilities of 23 ‘expert’ guide dogs.

The details of the tests are quite complicated. So I’m just going to summarise the keys findings. But do click on the link above if you want to know more.

The dogs were first trained to respond to the command ‘find the van’ and then, with a blindfolded instructor as handler, they were given four different tasks, each of which was designed to explore a different aspect of navigation: path-retracing, homing, shortcutting and detouring.

The dogs were first taken along an indirect path from the designated ‘home’ point to the van - just once. This gave them an opportunity to learn the route. Perhaps surprisingly, only 30% of the dogs were able to retrace the path they had followed on the outward journey. 43% were able to retrace the return route (‘homing’).

But this rather poor performance is apparently typical: guide dogs normally need three or four trips before they can reliably reproduce a route.

Now comes the exciting part.

80% of the dogs were able to take successful shortcuts on their way home, and 87% were able to find their way when an obstacle was placed in their path and they had to make detours. Errors increased as the route got longer - not surprisingly.

So even if most of the dogs weren’t very good at learning a route they had followed just once, a large majority were able to keep track of where they needed in order to get ‘home’.

The most obvious explanation is that the dogs are performing DR in some way. In other words, they are able constantly to update their geographical relationship to their ‘home’ as they travel away from it.

A magnetic compass would plainly be very helpful in this process, but the dogs would also need to be able to measure distance quite accurately. Some kind of odometer would seem to be required - perhaps based on step-counting.

That seems plausible enough in the case of the guide dogs. The journeys they were making were quite short: only a few hundred meters. But is it really possible that the dogs in Müller’s experiments (see previous post) were able to find their way home, just by using DR?

Even with a magnetic compass to track course changes, that would be quite a feat - especially after being carried in a closed basket along a circuitous route to a point 89 km from home! How could his dogs have measured distance?

Could their sense of smell have played a part? Or is something else going on?

Watch this space!

23.More about dogs and their mysterious homing abilities...

Last time I talked about Colonel Richardson’s work with ‘messenger dogs’ in World War I.

A fascinating feature of Richardson’s work was his discovery that all dogs were not equally adept at homing.   Drawing again on Michael Nahm’s review article, I now want to share with you the work of two later researchers.  As we’ll see, their discoveries amplify the very same point - but still leave us with a big mystery.

The first, Bastian Schmid, worked in the 1930s. He was apparently the first scientist to address directly the question of how dogs find their way home.

Schmid’s experiments involved only three dogs that were displaced to an unfamiliar location at a straight-line distance of some 4-5 km from their home. Two of them succeeded in finding their way back (one was tested in the middle of the city of Munich, the other in a rural area).  The dog released in the city homed over a distance of 4.5 km despite the presence of ‘street canyons’ that completely blocked the view. The third however failed completely on three occasions, even when he could have seen a familiar location.

Most intriguing was Schmid’s observation that the successful dogs “didn’t seem to use their noses”. They didn’t sniff for cues either close to the ground or in the air. “After an initial phase of orientation”, they simply trotted in a homeward direction “with raised heads”.

In the 1950s/60s, a researcher called Bernhard Müller carried out a much more elaborate series of experiments in Switzerland and Nepal involving no fewer than 75 dogs, both male and female. For some reason, Müller’s work seems not to have received the attention it deserves.

This is how Nahm summarises Müller’s approach:

“The ideal test series for a single dog consisted of four runs from the same release site at a distance of 2.5 to 3.0 km from the home territory, four runs from a different release site at 5 to 7 km distance and shifted clockwise through an approximate angle of 120°, and four runs from a distance of 10 to 89 km, shifted another 120°. Hence, a complete test series consisted of 12 runs that started at three different locations”

The dogs were carried to the release sites in closed baskets, usually via a series of complicated detours, and in all weathers (including snow and fog), both by day and night.

Just pause for a moment to consider: some of these tests involved homing from distances of 89 km. Could any dogs pass such a stringent test?

Well, the answer is yes!

Of the 75, no fewer than 19 completed the whole series of tests successfully.

Seven others did well at first but failed to complete the whole series successfully. 49 failed the first test and were then dropped.

Prior to the tests, Müller “determined the dogs’ social status by a number of selected behaviour characterics” and assigned them to three groups: dominant alpha-males, submissive omegas, and an intermediate group. He assumed that with increasing rank the ‘value’ of the home territory for the dogs would be raised. This in turn would, he predicted, result in a stronger homing impulse and greater success.

This proved to be the case. All 22 alpha dogs belonged to the group of 26 that either completed all the trials successfully or that started out well. The remaining four were high in the intermediate group.

None of the omega dogs returned home successfully. They just sought out humans or other dogs and then stayed with them. They showed no homing impulse at all.

The alpha dogs behaved very differently.

They would first spend a period of time near the opened basket (Müller called this the “adaptation phase”), and then left the release site, heading for home:

“On their way, they would avoid any contact with people. A very characteristic bearing of a dog on its way home … was to hold its head high and in a peculiarly stiff manner when trotting, its eyes appearing somewhat ‘veiled’. Often…they would stumble when the soil was uneven, or even collide with low wire fences”.

Müller noted that in general, “orientation by vision seemed to play a negligible role in their journeys”. And when they reached the same decision points on repeated tests (such as a ridge or pass), they would take different and typically shorter routes thereafter. It looked as if the dogs had “learned how to choose the correct direction in a general sense, and were able to adjust their routes accordingly”.

Müller was baffled by these findings, as well he might have been. He recognised that even if the dogs had access to some kind of compass, that would not explain how they determined their geographical position at the point of release - or how they could then select the right homeward compass bearing.

So we’re back to the same question: do (certain) dogs have access to some kind of cognitive map on which they can fix their position when displaced to an unfamiliar site - and on which they can also plot a course home?

This is a crucial question that arises in relation to many animals notably homing pigeons and migratory birds - like the cuckoos I discussed in an earlier post.

More of this soon!

22.The ‘messenger dogs’ of World War I…a little-known story of canine courage and skill.

In an earlier vlog post (“Canine navigation”) I discussed briefly the evidence that dogs have some kind of magnetic compass sense.

As I said, it’s been known for a long time that dogs are really good at finding their way home - even when taken to unfamiliar locations.

But I hadn’t then seen an important review article by Michael Nahm which summarises a lot of interesting early research on the navigational abilities of dogs. I wish I had known of it when I was writing Incredible Journeys/Supernavigators. It would have been worth a whole chapter!

Have you ever heard of Colonel Edwin Richardson who set up the ‘British War Dog School’ in 1917? The dogs he trained brought secret messages back to their handlers from the front line during the First World War.

Richardson first got interested in the homing ability of dogs when his own dog found its way home from the centre of Brighton, where it had got lost in crowded streets. It was the dog’s first visit to that city, and he was taken there in a carriage on a winding and “not at all direct” route.

Richardson’s house lay “several miles” behind Brighton, but the dog was seen heading towards the house in the evening, apparently travelling “over land he had never seen before, and in a totally different way of travel from that on which he had set out in the carriage that morning”.

Very puzzling!

This is how Richardson himself described the work of of his courageous ‘war dogs’:

“…the messenger dogs for the British Army were concentrated in units behind the line and were dispatched in groups to those parts on the line where particularly strenuous fighting was expected. They went up in the charge of their keepers, each man having three dogs. Having arrived at Brigade headquarters the keepers remained there and the dogs were taken from them by troops occupying the front line . . .

“They were frequently taken up to their posts at night, over ground utterly unknown to them previously, and were released some hours afterwards with their messages. Sometimes they returned by the way they had been taken up, but more often chose a more direct route straight across the country . . .

“It will be remembered that this would lead them over trackless ground, or along trenches and roads crowded with every sort of traffic, through villages full of troops and every sort of obstruction and temptation.

“That these dogs accomplished this work is one of the wonders of the war. How they did it cannot be fully explained, for the reason that we do not fully understand the influences which control the animals when under an overpowering desire to return to the place from whence they came. Suffice it to say that it was the determination to return to a beloved master, as represented by his keeper, and that as a result of this emotion, portents and signs indistinguishable to man were waymarks on the journey.”

Strangely enough, the dogs seemed to perform even better when the going was tough: “…when the conditions were so bad, the night so dark and thick, the ground so water-logged and shell-marked, and on certain occasions quite new to the dogs… the dogs seem to work much better than usual”..

As one of the keepers - who had been very worried that his dog, Jock, wouldn’t make it home - reported: “It seemed as though ‘Jock’ divined my fears, and put out an extra effort to show they were needless”.

But these amazing homing abilities were not equally distributed among all dogs.

Richardson “found it necessary at the training school to study the psychology of each dog as the bent was much more highly developed in some dogs than in others. Dogs of wise and affectionate natures were the only ones of any use in the strenuous work they had to perform in the field, and the great lever by which the homing instinct was initiated, was that of devotion to the man who was deputed to be the dog’s keeper.”

Richardson himself was baffled by the dogs’ navigational abilities which he ascribed to “an intelligence quite apart from, and infinitely above, any guidance from the senses”.

Well, we now know that dogs have a magnetic compass sense and that no doubt plays some part in how they manage such amazing feats, but that can’t be the whole story. A compass by itself is not enough. Maybe dogs really do have the ability to form ‘cognitive maps’ as well.

A fascinating recent article by Kateřina Benediktová and her colleagues (to which I owe my discovery of Michael Nahm’s article) sheds new light on this.

That’s quite enough for today, but don’t worry - I shall be returning to this subject soon. There’s much more to say!

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.

20.Mantis shrimps are celestial navigators!

New research reveals that mantis shrimps make use of a sun compass to find their way home. It seems to be based either on the sun's azimuth or on polarisation patterns in the sky (‘e-vectors’) - both of which are often visible beneath the surface, at least in shallow water.

When clouds conceal the sky, however, they fall back on DR or path integration.

They’re the first marine animals in which these abilities have been demonstrated, though many insects can do similar things.

Congratulations to the authors, Rickesh N. Patel and Thomas W. Cronin, of the University of Maryland.

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…