Scent rolling

One of the spectacles which we can usually guarantee to present visitors with when they walk with the wolves, is the sight of Peyto and Cheza indulging in one of their favourite, on-leash pastimes - rolling in muck. The sight of a 100lb master predator twizzling around on its back with a big, silly grin, pizzarising a cow pat never fails to evoke both humour and question.

The question is, of course, "why?" - and answering it is one of those perennial, awkward jobs because the answer is not brief and for most people, requires a shift in understanding. Unfortunately, even the juiciest cow-pat does not entertain a wolf long enough for us to give an accurate answer on the spot.

First of all, lets get one common misconception out of the way: They do not roll in smelly stuff in order to conceal their own scent whilst hunting. This is a confusion between what the behaviourists call the "function" of a behaviour and its consequence.

"Consequence" is the short-term outcome of a behaviour, The "Function" is its long-term or evolutionary advantage. The long-term benefit of rolling on a rotting mole may be that the wolf gets some survival advantage by getting a better meal later in the day but that does not explain what motivates them at the time when they roll on it. Saying that a wolf rolls on something smelly in order to assist some activity hours later is implying that the wolves perform long-chain, predictive reasoning - which they do not seem to. Also, it implies that the wolf 'contemplates' in the sense that it reflects, after a successful hunt, that the success was enhanced by something it did hours before the hunt and makes a mental note to do the same next time - again, hours before the hunt. If wolves could reason consciously like this then the human race could probably not exist in competition with them. They are intelligent and in some respects they have good memories but they don't think the same way we do.

The answer to the question is partly obscured by a couple of quirks of our own biology and demonstrates how well our species-bias leads to misinterpretation of other species' behaviours. The first quirk is the lack of a scent detection organ called the 'organ of Jacobson' (or vomeronasal organ). Most large mammals possess this organ - humans are one of the few that don't. It is located in the floor of the nasal cavity, just above the palatine bone and its purpose is to provide ultra sensitive detection of air-borne chemicals (smells), especially pheromones. The second quirk is the very small area of olfactory mucosa (smell receiving tissue at the back of the nose) which we possess compared to most other animals. We have around 3 square centimetres of olfactory mucosa compared to the average dog's 70-odd square centimetres.

It would be easy to indulge species bias again at this point and assume that all this just means that they smell exactly what we do for a given odour - but they smell it when it's 1000 times less strong. This is a gross oversimplification though What this all adds up to is that a wolf or dog's brain receives not just the "smell" of an odour but a full analysis of all its components. Comparing sensitivity is not easy and wild figures are often bandied about but, on average, most authorities agree that the sense of smell in wolves and dogs is somewhere between 1000 and 10,000 times "better" than ours and in addition, a very large percentage of the wolf's brain is devoted to analysing the information it gets from a smell.

The sensitivity and brain-processing power which wolves have available for scent detection and analysis renders their sense of smell about equivalent to our sense of sight - or perhaps, our highly developed sense of hearing (we have possibly the best all-round auditory system of all). The scent information is actually processed in a part of the brain called the rhinencephalon. This is located at the front of the brain and is much larger and more developed in most animals than it is in humans. Research has shown that a good deal of neural activity goes on in this region whenever an animal has to solve a problem; so you could say that, in a sense, they reason with their noses.

In fact, wolves' sense of smell should really be counted as a different sense from ours. To compare the two is a bit like comparing the phototropic response of a sunflower with our own binocular, colour vision. Wolves see details in scents that have no equivalent for us in any other sense than our sight. Indeed, our perception of the world is centred around our sense of sight. To us, scent information is mostly of secondary interest and often simply undetectable. By contrast, the information and sensory experience which a wolf gets from a smell is unimaginable to us and is central to its perception of the world. To the olfactory sense of a wolf, the world is a scent landscape; subtle and full of patterns, hues, shadows and impressionistic filigree - and information too. Our visual image of the world conveys to us not only just a fraction of the total information it contains but a totally different fraction from that sensed by the wolf. Their perception of the scent landscape is as alien and unimaginable to us as is the electric field sense of a shark.

So, to a wolf, a smell has all the complicated and interesting details that a visual object has to us. For example, the scent mark of another wolf conveys all sorts of information to the animal smelling it - details such as the age, sex, hierarchy status, health and fertility of the wolf which left it. Thus, to a wolf, smells are a source of information as well as pleasure and fascination. In other words, they are important to the wolf.

The next consideration in the answer to the original question is to do with wolves' desire to possess things. Wolves are born to possess; quoting from our previous article on wolf aggression: "How a wolf gains and maintains its rank within the hierarchy is a whole subject on its own but one of the major factors is the extent to which a particular animal can claim and control access to resources. The more control it has and the more it can keep for itself the more important it is - and 'importance' is obviously a key concept in rank and status. Wolves are born to possess. Anything which is of use or even just of interest is a desirable item to them and they will do their best to take possession of it and keep it…. to possess something is to be important, to investigate and understand it is to be even more important".

To a wolf, a smell is a fascinating and possessible - even beautiful - item; the equivalent to us of a beautiful painting or picture. The information it may contain is also important and ownership of that information confers importance upon the bearer. But the problem is that, unlike a material object such as a rotting, dead bird, they can't physically pick up a smell so how can they take it away ?

Simple! Roll in it.

Wolves and dogs are often seen to roll specific areas of themselves in smelly stuff and it is possible that they are accentuating the scent highlights of parts of their bodies as part of their status body language - or, in this case, scent language.

So, the answer to the question "why do they roll in smelly stuff?" is twofold. Firstly, the consequence of it is that they get to 'possess' it because they a) like it - it's a beautiful thing to them and b) think it important to own. Secondly, the function (evolutionary outcome) is that the scent may inform other pack members of new game or intruders in their territory or it may indeed conceal their own odour whilst hunting and thus improve their survival prospects - although the wolf is probably not at all consciously aware of any of these particular factors.