An overview of canine communication

Dogs communicate visually using movement and a wide range of body postures, which can be overtly expressive or incredibly subtle, such as an ear or tongue flick.

Gestures are controlled by voluntary muscles and convey information about how the signaller feels and what their intentions are.

Although each body part may be examined in isolation, it is important to observe the entire body, wherever possible, to interpret the emotional expression of the individual.

Challenges to visual communication

Artificial selection and human intervention have resulted in a wide variety of dog breeds and types, plus their crosses, with hugely differing morphology. For example:

• The subtleties of facial and body movements might not be clear in dogs with longer or wrinkled coats, or those with darker-coloured coats
• Dogs without tails, or tails that are carried high or twisted over the body, create differing silhouettes to those with tails which naturally hang downwards, and mean they are not necessarily able to be tucked beneath the body.
  This limits the individual’s ability to communicate anxiety or fear by tucking their tail beneath them
• Dogs with limited mobility or anatomical abnormalities might be unable to adopt certain postures or movements. As well as potentially causing frustration, this risks them not being able to communicate as quickly as they desire and might therefore result in more overt vocal communication, such as growling, to maintain feelings of safety.
• Limb amputees, as well as dogs with docked/short tails or cropped ears, have altered silhouettes which can restrict visual communication ability
• Dogs are able to learn that some forms of communication work out well for them and might therefore begin to perform these more often in contexts other than their original intention, for example:
  • some dogs have learned to bare their teeth toward humans as an affiliative gesture
  • some dogs have learned to enjoy having their stomach area stroked and will roll onto their backs to solicit this type of human-dog interaction
  • However, in both of these examples, the positive emotion of the dog will be displayed across the rest of their body, remaining relaxed and tension-free.

The above illustrates why carefully considered puppy socialisation is so important. It helps a puppy learn to interact with a variety of different types and breeds.

Under-socialised puppies, with minimal exposure to dogs other than their own litter, might therefore miss out on valuable learning about how different types of dogs communicate, as well as the subtle nuances of individuals.

Body

As dogs might observe each other from some distance, body size and posture often provide the first means of obtaining information about each other’s feelings and intentions.

For example, a dog may differentiate between other dogs whose muscles are generally relaxed and loose, and those who are tense and stiff.

Similarly, regardless of individual size, a dog can use techniques to make themselves appear either bigger or smaller.

Piloerection (erection of hairs) might be most evident, as the large muscles across the dog’s back become invigorated and tense, as well as tiptoe-standing to increase height/size, which can relate to anxiety, fear, frustration, or excitement.

During interactions that a dog finds uncomfortable, they can reduce their height/size by lowering their body and tail. This can be used in combination with flattening their ears back to express a desire to avoid conflict.

Tail

A dog’s tail helps to provide definition during posturing and can signal many different feelings, for example:

• tail relaxed but held high signals confidence
• potentially coupled with willingness to engage
• tail held stiffly signals anxiety and/or threat intent
• tail held low or tucked under signals fear, anxiety and/or appeasement
• tail held low with a quivering wag signals nervousness or internal conflict, for example, if there are two appealing options available and the dog can’t work out how to respond.

Face

Dogs can identify movements in and around the eyes, ears, and mouths of others. Both in fellow dogs and other species, differently coloured eyebrows and muzzles can help to make these gestures more visible.

Eyes

Eye contact plays a vital role in dog communication. They might stare at another dog as a means of intimidation or avoid eye contact to demonstrate non-threatening appeasement.

Dogs can gauge another’s willingness to interact based on their desire to make, maintain, or avoid eye contact. In stressful or difficult situations, a dog’s eyes often widen to expose the sclera (white of the eye) often referred to as ‘whale eye’.

In contrast, however, when interacting with humans, dogs naturally attend to the eye region and can find eye contact with humans reinforcing. Consequently, dogs can readily offer, maintain, or even solicit eye contact as a means of interspecies communication.

Ears

A dog’s ears can be rotated to various degrees (depending on an individual’s morphology) and may communicate the following:

• held or flicked backwards/lowered signals appeasement
• flattened/pressed backwards/lowered signals fearfulness or antagonism
• held forwards signals interest, willingness to engage/attend/approach/investigate.

Mouth

The mouth, including labial (lip) movement and tooth display, can signal extremely important information about an individual’s intent and emotional state, for example:

• loosely open mouth with teeth hidden, softened lips and tongue loose or lolling out signals relaxation
• tense, taut lips with closed mouth and commissure (corners of mouth) drawn forwards signals arousal, nervousness, tension
• lips pulled back and panting signals distress or arousal
• teeth-baring/snarling to either display canine teeth, full incisor or arcade display signals antagonism, fear, or rage.

The range of dogs’ vocal-signalling repertoire appears to have expanded during domestication, which suggests that social interaction with humans has been influential in regulating vocal expression.

Barking is the most typical vocalisation. Barking is generally performed in short-range interactions, in a wide variety of contexts such as warning/alerting, greeting, attention-seeking and play.

Barks convey functional information expressing the signaller’s emotional experience within a specific context. For example, a dog might bark with a lower pitch when worried by an approaching stranger, but with a higher pitch during isolation.

Growling is mainly performed as a warning or threatening signal during combative situations, or during play. Dogs can differentiate between growls produced in different contexts, so can work out if they are ‘positive’ or ‘negative’.

Growling might increase in duration and volume according to an escalation in discomfort. It might also be accompanied by other signals, such as a lip-curl to display the canine tooth and widened eyes with ears held backwards.

Whining may indicate pain, stress or excitement. Whining might be performed specifically to gain attention, especially where a dog has learned that this vocalisation results in their owner attending to them.

Howling is a form of reunification behaviour, aimed at maintaining social unity.

Other forms of vocalisation include groans, yelps, grunts, sneezes and puffing out air from one’s cheeks. Grunts and groans may indicate pleasure or pain depending on the context in which they are performed.

Dogs’ high olfactory sensitivity allows them to access chemically derived social and contextual information through their sense of smell.

It is important to remember that the chemical signals within urine, faeces, saliva, sweat, shed skin/hair cells and glandular secretions are also spread around a dog’s environment, for example, a urine stain upon a tree.

These chemical signals allow a dog to obtain social information without the need for physical contact or interaction.

Although depositing of scent can be circumstantial, dogs are able to intentionally deposit odour with communicative intent – for example, an entire male dog might urinate on or near an entire female’s urine mark to demonstrate availability for mating.

During social interactions, dogs engage in investigative sniffing behaviour as part of greeting rituals, prioritising specific focal areas of the body such as the face, neck, inguinal and perianal areas.

Dogs can also recognise humans by individual smell and identify changes in human biochemistry – for example, glucose levels – and adjust their behaviour according to the chemo-signals they detect.

A dog can also use olfactory information to interpret human and animal emotions such as fear and respond accordingly.

Pheromones are chemicals emitted by the body for detection by individuals of the same species. They are believed to influence social and reproductive behaviour.

Just like environmental odours and other chemical information encountered, pheromones are filtered through a dog’s vomeronasal organ (VNO).

The VNO sits within the nasal cavity and is the anatomical structure responsible for detecting chemical communication.

Although it's still not fully understood, it is believed to operate like a filter, enabling the dog to differentiate between social and non-social chemical information.

Tactile communication is a typical feature of human-human communication. However, between dogs, it appears to generally occur within specific contexts such as during mating, during agonistic interactions to intimidate an opponent or to maintain a unique social bond.

Social cohesion appears to be maintained by specific activities in particular, such as resting in close contact, sexual approaches preceding mating, and social grooming. However, this context-specific tactile behaviour tends to be short-lasting.

Humans tend to initiate and seek to maintain physical contact with a higher frequency and for a longer duration than dogs. For this reason, some dogs may appear less relaxed during human-dog tactile interaction and tolerate –rather than solicit and enjoy – physical contact.

Some dogs might even attempt to avoid or withdraw from such interaction, but this will likely depend on which specific part of their body is being touched, as well as the manner in which they are being touched.

For example, a dog’s reaction could be different to different types of tactile contact such as lying on a lap, being stroked, being hugged and being picked up.

Just as dogs learn that making eye contact with humans can have positive outcomes for them, dogs can learn to enjoy physical tactile interactions with humans, especially when carefully introduced from early puppyhood.