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!

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!

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.

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?

7.Celestial navigators - human and non-human

People have been using the sun, moon and stars to help them find their way for a very, very long time.  

And not just people but other animals too – like birds, moths and beetles – to name but a few.  This is a really exciting area of research and new discoveries keep piling in, many of which are described in Incredible Journeys.

Eric Warrant and Marie Dacke, for example, have shown that nocturnal dung beetles roll their carefully sculpted dung balls back to their nests using the light of the moon or the Milky Way as a guide.  

And recently Eric Warrant and David Dreyer have shown that the Australian Bogong moth also makes use of the Milky Way to maintain a steady course on its 1000 km migratory journeys (as well as a magnetic compass).

Bogong moth

We know that many birds that migrate by night orient themselves by paying attention to the rotational pattern of stars around Polaris, which marks the direction of true north.

My guess is that our prehistoric human ancestors would also have been pretty good at this kind of celestial navigation - tens of thousands of years ago.

What we know for sure is that the builders of Stonehenge and many other ancient monuments around the world are carefully aligned so as to highlight key celestial events like the summer and winter solstices – that mark the longest and shortest days of the year.  

And the amazing Nebra Sky Disc – discovered in Germany in 1999 – suggests that our Bronze Age forebears understood the very complicated relationship between the solar and lunar years.  It was made about 3,500 years ago. http://www.bibliotecapleyades.net/arqueologia/nebra_disk.htm

And the Greeks knew a thing or two.  The amazing Antikythera Mechanism – discovered by sponge divers over a hundred years ago – dates from around the end of the 2nd century B.C.  It’s by far the most sophisticated mechanical device yet discovered from the ancient world. The Antikythera Mechanism seems to be a complex mechanical “computer” which tracks the cycles of the Solar System: https://en.wikipedia.org/wiki/Antikythera_mechanism

We know frustratingly little about how the Greeks and Romans navigated at sea, though they travelled widely - and not just in the Mediterranean.  It’s always assumed that they didn’t use any specialised equipment.  But the Antikythera mechanism makes you wonder…if they knew that much about the behaviour of the heavens, would they not have put their expertise to navigational use?

On the other side of the world the islanders of the Pacific were already starting to venture out across the Pacific at least two thousand years ago. In their ocean-going sailing canoes they could make accurate landfalls on small islands after travelling as much as two thousand nautical miles across the open ocean.  

They didn’t use any instruments or even charts.  They relied only on their wits and finely-tuned senses – and a lengthy apprenticeship that started when they were children.  When western sailors like Bougainville and Cook first encountered these navigational prodigies in the mid-18th century they were astonished.  

Luckily we know a lot about how the Pacific Islanders navigated because, back in the 1960s, researchers started asking the right questions - before their extraordinary skills had completely died out.  

At the heart of traditional Micronesian and Polynesian navigation was an encyclopaedic knowledge of the sky.  The master navigators knew exactly where on the horizon 32 bright stars rose and set, and they could steer a steady course by reference to them.  They also understood that Polaris indicated where true north lay and during the day they could steer by the light of the sun by accurately allowing for the its gradual movement across the sky. They had many other remarkable skills and happily these are now being widely practised once more: http://hokulea.org

Before electronic aids like GPS arrived on the scene, navigators everywhere learned to observe the world around them very closely.  The colour of the water and its depth, the composition of the seafloor (tested with a lead-line), the behaviour of birds, the shape and colour of clouds – these and many other signs could give early warning of the presence of land, often long before it could be seen.

In former times, sailors everywhere paid the closest attention to the world around them - as well as the skies above them. Safe navigation depended on complete immersion in the natural world. It may not always have been as safe or reliable as navigating by GPS, but it was a far richer and much more rewarding experience. And it was also a great deal more robust: no problems like flat batteries, solar storms, spoofing or jamming!

4.How do whales navigate?

A recent article in The Atlantic discusses the fascinating possibility that whales make use of the Earth’s magnetic field to help them navigate the oceans.

As I explain in Incredible Journeys, many great whales (including notably the humpbacks that migrate annually between the Antarctic and equatorial waters) regularly travel for thousands of miles across the apparently featureless open ocean following remarkably straight courses. Since they seem to be able to do this even when the sky is obscured, it seems unlikely that they rely on celestial cues (like the sun or stars) to perform these feats - though it’s conceivable that they can do that too in fine weather. The omnipresent geomagnetic field (see my earlier post ‘The great magnetic mystery’) would however be available to them at all times and places - and all depths.

The theory that whales may be magnetic navigators (like many other animals including some birds and insects) has been around for a long time. But Jesse Granger and her colleagues at Duke University have recently published some interesting work based on a review of data gathered over a 31-year period. They wanted to find out whether solar storms that disrupt the Earth’s magnetic field are correlated in any way with strandings of gray whales.

They looked at 186 strandings involving apparently healthy whales (injured or sick animals might get stranded for other reasons) and parallel data relating to levels of solar activity. They found that the two were indeed closely correlated.

So what’s going on?

As Granger et al. explain, ‘Solar storms could have two impacts on magnetic orientation. They could alter the geomagnetic field, leading to false information, or disrupt the animal’s receptor itself, leading to an inability to orient.’ But the key factor influencing the strandings appeared to be the increase in radio frequency ‘noise’ associated with the solar storms rather than any displacement of the Earth’s magnetic field.

Granger et al. conclude: ‘These results are consistent with the hypothesis of magnetoreception in this species, and tentatively suggest that the mechanism for the relationship between solar activity and live strandings is a disruption of the magnetoreception sense, rather than distortion of the geomagnetic field itself.‘

There is evidence from studies of migratory robins that RF noise (from AM radio transmitters) can disrupt the magnetic compass sense of these birds. It’s possible that the hypothetical cryptochrome magnetoreception mechanism may be disrupted by such transmissions. So, as Granger et al. acknowledge, it’s conceivable that whales may also rely on a cryptochrome-based magnetoreceptor. But it’s far too soon to start laying bets!

One thing that puzzles me is that gray whales - which tend to follow the coast on their migratory journeys rather than crossing the open ocean - should be so heavily reliant on magnetic information that they would get stranded if it was disrupted. Could they not simply use landmarks or the contours of the sea floor to help them find their way? And even if they did rely on their magnetic sense of direction, you’d think that they would notice when the water began to shoal and turn back before they went aground. It’s odd.

The humpbacks by contrast are prodigious oceanic navigators and it makes sense that they would rely on geomagnetic cues when out of sight of land. Interestingly their migratory journeys often seem to feature visits to underwater features called seamounts. Could it be that these act as waymarks? Maybe they even have unusual magnetic properties that the whales can detect?

Apparently Granger is now looking at 12 years-worth of data relating to humpback whale voyages. She wants to see whether they have more difficulty maintaining straight courses when solar storms hit the Earth.

That should be interesting!