Wolves, as most species, communicate through different avenues – some are more researched (and researchable) than others. For example, sound and scent are fairly well documented whereas touch and taste are less easy to investigate. One particular way of communication can also be integrated with one other or more different way, for a complex combination of signals that wolves are born and learn to understand.
Sound – Auditory Communication
When one thinks of wolf communication, probably the most popular signal that comes to mind is the howl. However, most auditory communication in wolves involves close-range, fairly quiet sounds – many of which are learnt right at the start of a wolf’s life in its neonatal pup phase. The earliest vocalisations wolves express are squeals, screams, yelps and yawns. Because pups are deaf during this neonatal phase, such vocalisations are probably designed to target only their mother, but not all of these noises get a reaction. For example, squeals tend to be ignored, while screaming generally encourages a mother wolf to reposition a pup or groom it. Other common vocalisations are moans, whines, growls and barks. Moans, like squeals and screams, are most common in neonates under two weeks of age. Although pups are deaf, moaning (possibly thought to signify contentment) is often observed while animals are huddled together – perhaps they detect the vibrations of littermates’ vocalisations and it brings a sense of reassurance.
Woofs, squeaks and howls are vocalisations that are used from about three weeks of age onwards and are more characteristic of adult auditory signals. ‘Woofs’ are most performed by pups when they detect adults near the entrance of their dens, and in the absence of their mother – such vocalisations thus probably reflect uncertainty. Howling in pups becomes most common after several weeks as they finally start venturing outside. As they spend more time out with adult wolves they tend to join in daily howling with other pack mates. However, howls (and other pup vocalisations) tend to have a higher frequency than those of adults until an animal is about 6-7 months old – until then a pup’s voice does betray its young age.
At adulthood, most vocalisations are used in close range in conjunction with other communicative information (e.g. visual, tactile, olfactory). Different auditory signals can also be used together in one certain context. Contexts and their associated short- and medium-range vocalisations include:
Pain, fear – yelps
Greeting – whimpers, whines
Frustration, anxiety – yelps, whimpers, whines, moans, growl-moans
Submission, appeasement – whines, moans, growl-moans
Dominance – moans, growls, snarls
Threat, attack – moans, growls, snarls, woofs, barks,
Warning, defence – moans, growls, snarls, woofs, barks
Protest – growls, woofs, barks
Play – whimpers, whines, moans, growls
Sexual arousal – whimpers, whines.
Long-distance vocalisations evolved due to constraints in the environment through which sound travels. Landscape features (e.g. hills, valleys, vegetation) and factors of the air itself (e.g. temperature, humidity, turbulence) are some contributing aspects. Howls have been developed accordingly to contend with such factors. A single howl can be heard a maximum of 10km away in a forested habitat, and 16km away over tundra. This long range comes at a cost in the actual structure and variety possible with a howl; less subtle information is able to be conveyed.
Wolves howl alone and in groups. Solo howling is most common during the breeding season in the mornings and evenings – the peak activity times for wolves, and it signifies a single animal searching for a mate. Solo howls tend to be quieter than a pack howling together; because of a howl’s range its exact audience is unknown, especially if a wolf is in a new territory or has been separated from its pack. Attracting attention by an unwelcoming pack is generally unwanted by solo wolves, thus they tend to limit the amount of information contained in their howl. Pitches can be changed in relation to the type of message an animal is seeking to portray, and each wolf’s howl varies individually so it is a way of communicating personal information.
Howls in a chorus can be even more variable than those from a single wolf. A chorus will generally be started with a relatively unmodulating howl, but as other wolves join in the pitch and frequency becomes increasingly varied. During these choruses wolves may also bark, growl and squeak, adding even more variety to the overall sound. Wolves readily howl when separated from pack members before being reunited – it can serve as a tracking function as well as for social bonding, mating and reunion. Due to the varied qualities of each individual’s howl it can help separated pack members distinguish each other from intruders.
Scent – Olfactory Communication
Olfaction (the sense of smell) is probably one of the most acute of the wolf’s senses and the one they rely on the most. In fact, a study published in 1986 showed that wolves, even once made anosmic (unable to smell), would continue for years to sniff at objects as if seeking olfactory information even though they would be physically unable to find it.
Olfactory signals add more information to communications wolves may have received from other means – e.g. a male wolf may encounter a female who’s vocalisations may convey she is not willing to mate, but the scents in her urine may indicate that she is physiologically ready. Auditory communication provides information about an animal’s very current state, whereas olfactory signals last much longer. For another example: howling portrays an animal’s location, mood and identity instantaneously, while scent markings show the same information and more (gender, breeding condition, social status, emotional state, age, diet) while lasting days or even weeks.
Skin glands play an important role in olfactory communication. The three types of secretory skin glands are sebaceous, apocrine and eccrine. Sebaceous glands are typically found in hair follicles and produce an oily, waxy substance called ‘sebum’ that emits distinct odour when combined with specific bacteria. Apocrine glands are known as sweat glands. These glands are most numerous on the face, lips, back and between a wolf’s toes. They discharge watery secretions that are not used for cooling. Eccrine glands are the true sweat glands; they function primarily for cooling, and secrete salty fluid directly onto the skin.
As mentioned, secretions themselves tend to be odourless but can produce an odour when acting with microflora in ducts or on the skin. Differences in microflora and in wolf diet change the chemical compounds created, thus allowing distinctive ‘odour fingerprints’.
There are apocrine sweat glands at the base of the toes and many numerous eccrine glands in the footpads. Wolves are sometimes seen scratching the ground after urinating or defecating – this may provide extra scent marks. Scratching may also provide visual marks that could draw attention to the associated urine or faecal deposit.
When a canid raises its hackles, it is a readily recognised visual signal. There may also be olfactory signals involved: on a wolf’s back the skin tends to lie in folds when the hair is not raised, thus creating an optimal environment for glandular bacteria to survive. When the hackles are raised and the skin folds are spread open, this may allow a passive release of scent. Again, different bacteria break down compounds in different ways – they can also break molecules into smaller, more ‘volatile’ and spreadable forms.
Anal glands contain both apocrine and sebaceous glands which are surrounded by a muscle layer under voluntary control. Anal gland secretions vary from season to season and between animals who are neutered and who are not; they give information about gender and reproductive state. Some anal sac contents can be deposited when defecating. It has also been observed that anal sacs are emptied in times of acute stress, such as when cornered.
Saliva may also contain information on gender or reproductive state. For example, male dogs have been observed to more frequently lick the muzzles of females than those of other males. It may also play a role in social bonding e.g. through mutual grooming between pack members (especially mates), and with a mother and her pups.
Faeces and urine are both used for territorial defence scent marking. When it comes to olfactory communication, urine is the most widely used signal. Urine marking is especially observed at areas where other wolves or even other canid species have been detected. Through avoidance of areas where an unfamiliar scent is noted, the likelihood of aggressive confrontations is reduced – and this is seen in wolves. Urine marking can also carry visual signals – for example when a male wolf raises his leg to urinate. In dogs, even just seeing another male raise his leg to urinate can trigger an individual to do the same. Raised leg urination may be beneficial because it allows an animal to place its scent at nose-level for the desired audience; thus it is more likely to be detected. In dogs it has also been suggested that the height of the scent mark may reflect the stature of the marker. Breeding females sometimes also slightly raise or flex their legs during urination – it can be year-round, but is most common during the oestrus period. During breeding seasons mated pairs may also tandem-mark, where one individual urinates then the other lays their urine scent on top. The frequency of double marking is highest in newly formed pairs. Wolves and other species also frequently roll in objects or areas that omit a strong scent such as a carcass, or a patch of ground where another animal has urinated.
Visual communication in the wolf was first described by a researcher, Rudolph Schenkel, in 1947, whereby he identified the most important features of this communication type as being the face (broken down into ears, eyes, lips, teeth, nose and forehead), the body (posture, hair) and the tail. He also suggested that facial and body colouration can enhance a signal’s value. Variation in these features was presumed to express a certain message along a continuum from aggression/confidence to submission/anxiousness. Aggressive or self-assertive individuals are characterised by a high body posture, stiffly-held legs and slow, deliberate movements. To enhance dominant stature hackles can be raised, hair
along the general back and up the tail can be bristled to portray a larger body size, teeth may be bared and nose and forehead wrinkled. Visual clues indicating submission or the readiness to flee (flight) include sleeking the hair against the body to portray a smaller body size and hiding the teeth. Especially submissive individuals carry their body low with ears back, and tail and head held low.
The tail is an extremely expressive and important feature on a canid. It can increase the visual size of an individual and may also give it a mechanical advantage in the event of a fight. Tail movements in animals about to initiate a fight are slow and stiff, whereas a submissive individual will keep a low tail and wag it, even involving the hindquarters in this movement. Most forms of intra-pack conflicts are solved by behaviours being expressed appropriately allowing for avoidance of an actual physical fight.
Schenkel described two forms of submission; active submission and passive submission.
Active submission: A submissive animal will actively approach another wolf in a low, slightly crouched posture, it will hold its ears back and close to its head and keep its tail low. The submissive wolf will wag its tail or hindquarters and will attempt the puppy ‘licking-up’ behaviour around the other wolf’s muzzle. Active submission occurs during one-on-one greeting or group interactions.
Passive submission: This type of submission is generally a reaction to an approach. A submissive animal will lie partly on its side and partly on its back, exposing its belly with its tail curved between its legs and ears flat and directed backwards. If the approaching individual investigates near the animal’s genital region the submissive wolf may raise an upper leg to expose even more of the belly area.
There are, of course, many variations of submission and the ‘extremity’ of expressed behaviours.
Wolves require a visual system that combines reasonable acuity (sharpness) with the ability to operate well under the low light available when wolves are often active. They possess duplex (“24 hour”) eyes that are adapted to functioning both day and night. However, the ability for this low-light sensitivity comes with a loss in visual acuity, but it is believed that wolves do have sharper vision than dogs. They are also better at distinguishing among shades of grey, and are very sensitive to motion. Their eyes have the ability to distinguish between the blue-green colour ranges, but have no sensors for the colour red – thus, a red flower looks pale green to a wolf. Although wolves lack the high definition and colour resolution of the human eye, they have the ability to use their visual system well into darkness. At night, although they lose colour vision and suffer further deterioration in acuity, they can still discern the features of nearby pack mates. White facial features patterns of many wolves may facilitate visual communication at night, and can also help during spread-out hunting trips enabling wolves to keep track of pack mates without shifting their gaze from their prey.
Touch – Tactile Communication
As mentioned, tactile communication in wolves has not been studied as extensively as other communication means. Touch does undoubtedly carry important information though – for example newborn pups who are deaf and blind rely on signals from touch to cue them to urinate and defecate, and they are still able to nurse and huddle. After their eyes open this huddling behaviour continues for up to several months, especially in colder temperatures.
Socially directed actions, such as play, involve frequent body contact. Food-begging involves physically licking another wolf’s muzzle, and active submission continues this snout-to-snout contact throughout life. Licking of fur also occurs – especially during mating season, and when a pack mate has an injury. Tactile communication may serve for strengthening social bonds through the reduction of stress. This can be observed in studies between humans and their pets where stroking an animal’s fur reduces heart rate and blood pressure in both species involved.
Contact during aggressive behaviour may also play a role in assessing a rival. Information gained through physical contact during play and ritualized fighting may indicate the strength of skill of an opponent. Of all the communication types (olfactory, visual, pitch of voice, etc.) tactile assessments bring about the most accurate current information about a rival.
Captive wolves have been noted to grasp the hands of human visitors with their mouths. This was something I once observed at the White Wolf Sanctuary – while most wolves would lick my hand on contact, Odot, a fairly ‘dominant’ wolf actually took the hand of a stranger in his mouth (let it be noted that pushing your hand through the fence is strictly forbidden, but as I said in a previous post, visitors often tried to push the rules). This has been recorded in other facilities – often the humans in question would notice that a wolf would hold their hand for several moments, increasing jaw pressure, and would let go just as the person began to feel pain. It has been suggested that this could be a similar equivalent to a firm handshake between humans, or perhaps it is a warning demonstration of dominance.
Taste – Gustatory Communication
The role of taste in wolf communication has also been difficult to assess. It also usually greatly interacts with other signals such as smell. Dogs have been found to possess receptors for salt, bitter, acid and sweet – thus wolves probably do as well.
Taste may be involved in the transmission of pheromonal information contained in urine and other substances. It may also be involved when adults and pups lick the muzzles of other wolves for food-begging. Grooming stimulated by blood on the muzzle or head of a pack mate may be reinforced by taste. The methodical grooming of pups by their mothers suggest that their fur may contain a pleasant-tasting substance not present in older animals – but again, all of these examples could be spurred on by scent signals.
While more research needs to be done into wolf communication, we know by now that wolves are complex beings that have evolved to use a range of communicative signals for an array of contexts. It is interesting to compare the behaviour of wolves when looking at our own domestic dogs, many of who also express these behaviours to perhaps a less-intense level.
For this and other information see:
Behavior, Ecology and Conservation
Edited by L. David Mech and Luigi Boitani