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!