Dogs really need to get out and check their messages on a daily basis, in the same way that we humans need to go to the post office or check our e-mail on a regular basis.

I realized this some years ago while walking our old dog, Joule, but at 12 years of age she was no longer quite as desperate about making the rounds.

After she vanished in mysterious circumstances last November, we went for a while without a canine companion until we finally gave in to the photos of eight cute puppies displayed at the post office.

Shadow joined us in December when she was just a couple of months old and, though she was used to being outside while living at the humane society shelter, was initially resistant to going for more than a short walk.

Within a few weeks, however, she got larger and more resistant to the cold, and more and more interested in the walk so that instead of dragging on the leash she was pulling ahead – and what she was pulling ahead to “see” was the chain of messages that had been left behind (you’ll pardon the reference) by other passing dogs.

I put “see” in quotation marks because dogs experience the world through their noses much more than through their eyes. And when it comes to communication, much of what they experience is what what others have, quite literally, left behind them.

Over the last few months of taking various strolls around our neighbourhood, I’ve come to call it all P-mail.

P-mail comes in two varieties – pee-mail (P#1) and poop-mail (P#2) – and is also colour coded.

Streaming P-mail comes in various shades of yellow and is especially evident in winter on piles of snow pushed up by the ploughs. There’s a lot more of this variety than the other, and it not only carries a sort of caller ID stamp but also marks the territorial boundaries of the depositor.

Male dogs apparently mark their territory a lot more than female ones. Joule seemed quite happy to leave no more than two streaming messages while we were walking, while I have seen male dogs pause every few hundred yards and offer their distinctive contributions to the network.

Shadow doesn’t leave a lot of messages yet, but eagerly runs from one mail drop to the next while we are out together, excitedly reading whatever messages have been left behind. I suspect that if we ever meet some of these dogs she will immediately know them by scent.

The second type of P-mail has a brown colour signature and has a more dense configuration of data. If streaming P-mail can be described as two dimensional in nature, the second variety is solidly three dimensional. It must contain a lot more information than the first type since all dogs that I have observed spend a lot longer reading the messages deposited at these mail drops.

We know from Farley Mowat’s memoir, Never Cry Wolf, that P#2 deposits not only contain personal information but can also reveal details about diet and geographical boundaries, so it stands to reason that it would take longer to read the messages. This may also explain the (somewhat disturbing) canine predilection for data sampling.

However the system works, it is clear that our canine friends find it all quite compelling and are eager to get out there and check their messages as often as possible.