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!