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Identifying expressive and meaningful body parts is integral to dog communication and emotional expression (see Figure 1.1; see General Appendix A for a canine body language ethogram). Meaning should not be obtained from any single body part or behavior in isolation. Instead, meaning takes shape when considering the totality of dog communicative behavior as well as environment and social contexts. To this point, observing and describing behavior precedes ascribing function, and individual differences in behavioral expression are commonly documented—even in response to the same stimulus or context. Research‐based resources provide background for visual communication descriptions (Beerda et al. 1998; Bradshaw and Rooney 2017; Miklósi 2015; Schenkel 1967), and visual representations of dog behavior and communication, such as Aloff (2005) and more recently Chin (2020), aid the study and recognition of visual signals.

Figure 1.1 Body parts that contribute to canine visual communication.

Source: Illustration created by and used with permission of Natalya Zahn.

Dog size and postural movements are observed by dogs and people alike. Unlike body size, posture can be modified to expand or contract, the former suggesting confidence or alertness and the latter conveying fear, prevention or reduction of conflict, or affiliation (Schenkel 1967). Dogs reduce size in multiple contexts and with different communicative meanings. A dog lying on the back in “passive submission,” often with ears back, tail tucked, and the inguinal region exposed, deescalates conflict and inhibits attack. Dogs can also display a more inviting “belly‐up” posture to solicit a belly rub. Alternatively, “active submission” may not be motivated by deference or a response to threat (Bradshaw and Rooney 2017). Instead, approach with low posture, low wag, and muzzle (or mouth) licking is an affiliative display to gain food, greet, or maintain or restore social bonds.

In interspecific contexts—such as if a dog has done something an owner deems wrong— submissive displays can be misinterpreted as a dog’s knowledge of wrongdoing. Instead, behaviors such as freezing, approaching or retreating with a depressed posture, low and quick wagging, ears back, or rolling onto the back or lifting a paw are best viewed along ethological lines as cohesive displays and non‐threatening appeasement postures to keep the group together. Research finds these behaviors are not indicative of a dog’s “knowledge” of misdeed or an admission of guilt (Horowitz 2009a).

Dog body posture can encourage “coming closer” (distance between individuals decreasing) or “backing up” (distance between individuals increasing), and a dog's body‐weight distribution offers subtle yet valuable information. A dog with weight shifted forward and upper body pressed over the front legs shows forward momentum, interest, confidence, or alertness. If a dog leans forward toward another dog—and the receiver leans back, looks away, or moves away—the second is engaging in conflict avoidance or communicating the dog’s desire to avoid closer interaction. If signals go unheeded, dogs may resort to defensive aggression over time and even fade out the use of distance‐increasing signals.

Limbs are central to body‐weight distribution and dog movement. While people may take note of limbs in the context of parlor tricks like “high five” or “give paw,” these gestures bear no social meaning for dogs apart from possible food reward or human praise. Instead, “offering a paw” is a submissive or appeasing display and, for example, may be performed in response to an upset owner. Sweating paws could indicate acute stress, but these are difficult to interpret as they could be related to other factors, like temperature (Polgár et al. 2019).

Piloerection is a physical response outside a dog’s control akin to getting goosebumps. This reflexive response can be seen in a dog’s hackles, or erect hair. Hackles run from the base of the tail to the shoulders, and because raised hackles indicate arousal in general, piloerection should be evaluated in conjunction with ear, tail, mouth, and overall body posture to assess specifics of the aroused state.

Tails are integral to communicative signaling. They can assume a range of heights, movements, and speeds, and even the side‐of‐wag offers meaningful information. Observing the tail‐base provides details as to whether the tail is being carried along the midline or is raised or tucked. Generally speaking, a high tail indicates excitement or arousal, and a high tail can be seen in a variety of approach‐oriented contexts ranging from greeting and playing to fighting and threatening; lowered tails suggest fear, submission, or appeasement/affiliation (Kiley‐Worthington 1976). To explore the value of tails within intraspecific communication, Leaver and Reimchen (2008) designed a study where dogs encountered a mechanical dog outfitted with tails of different lengths (long or short) that could move or remain still. Dogs were more likely to approach the mechanical dog when the tail was long and wagging as opposed to when it was long and still, suggesting that absent other communicative signals, dogs interpreted a wagging tail as “friendly.” On the other hand, a short tail, whether still or wagging, was approached similarly, suggesting that short (or docked) tails might be more difficult to view or interpret. Tail absence or surgical shortening affects communication (Bennett and Perini 2003).

Probably the most noticeable component of the tail relates to movement. A tail wagging fluidly and loosely from side to side (usually at the level of the midline) is most readily associated with greeting or excitement. This “happy” tail might be accompanied by jumping, licking, running in circles, or other behaviors of arousal. A tail wagging low and quickly indicates nervousness or timidity. High, fast wags indicate arousal, and they should be viewed with some caution. Arousal can take different forms, such as general excitement, interest in interacting, or even aggression. There are further individual variations in wags—circling, going more counter‐ than clockwise, banging—whose significance has not been studied (and should not be assumed). Tails can also lack movement and be held in a stiff, still position at all heights, which could either be the dog’s natural tail position or a postural display. Stillness is common in dog interactions: for example, play incorporates entire body pauses (including the tail) interspersed within fluid movements and play signals. Outside of play, a still tail should be evaluated along with the entire body to assess meaning.

While often imperceptible to the naked human eye, wags can be performed asymmetrically—more to the right or left of midline—and offer insight into stimulus perception or emotional valence due to brain lateralization hypotheses (Siniscalchi et al. 2021). For example, dogs wagged more to the right side when encountering an owner (suggesting positive valence), while the sight of an unknown, unfriendly dog, prompted more left‐side wags (negative valence) (Quaranta et al. 2007). When observing other dogs wagging more to their left side (negative valence), the observer dogs displayed increased cardiac activity and more stress behaviors, suggesting dogs may assess tail asymmetries in their interactions with other dogs (Siniscalchi et al. 2013). Ultimately tails vary in appearance and position such as curled, tucked, or falling to one side, and tails should be evaluated in relation to a normal, relaxed position.

Dog facial expressions and head movements contribute to visual communication, and the mouth imparts numerous signals (Bradshaw and Rooney 2017). Observing whether the mouth is open versus shut is the first consideration, and further qualitative elements provide more detail. An open, relaxed mouth indicates a comfortable dog, while a “tight mouth” could indicate emotional or physical discomfort or fear. Yawns can indicate a soporific state, but context and other behaviors may also indicate a stress‐related behavior. The corners of the mouth, or labial commissure, are also meaningful. A “long lip” describes when the commissure is pulled back toward the ear and is often seen in fear, distress, or appeasement displays. In a submissive grin, the lips are retracted, and the teeth are visible, but the eyes may be squinty and the forehead smooth as well as ears pulled back. A “short lip” is pushed forward, forming a tight forward‐moving “c” shape of the mouth. This is part of an aggressive display: the top of the muzzle is wrinkled, and the eyes are open and “hard”. Mouth positions may be fleeting and challenging to notice, and shelter staff and volunteers may benefit from concerted practice observing subtle dog mouth positions and their relation to other body positions.

Dog tongues hang generously from mouths during play, and a panting tongue in this context can be a sign of pleasure. Panting can also serve as an indicator of acute stress or physical discomfort (Beerda et al. 1998), especially when seen outside the contexts of activity or thermal stress. Oral behaviors, like mouth licking, are often—but not always—identified in situations of stress, pain, or uncertainty (Owczarczak‐Garstecka et al. 2018), and they are also a component of appeasement and greetings/active submission. In one study, dogs viewing angry human faces displayed an increase in “mouth licking,” suggesting that they may find angry facial expressions aversive (Albuquerque et al. 2018). “Tongue flick” or “tongue out” is described as the tip of the tongue extended and retracted quickly outside food or eating contexts, while “snout licking” describes the tongue moving along the upper lip possibly near the nose (Beerda et al. 1998). Dogs also use tongues socially to investigate substrates and surfaces.

Eye‐tracking studies find that dogs attend quickly to the eye region of other dogs (Somppi et al. 2016). A “hard eye” can be present before or during a threat and include a direct and prolonged gaze, sometimes with dilated pupils. A stiff, unwavering body posture may accompany this type of eye presentation. Pupil dilation—caused by activation of the sympathetic nervous system—indicates arousal, but further contextual information is needed to determine whether it is distress or eustress (Polgár et al. 2019). Conversely, “whale eye” is a label applied when the sclera of the eye is visible; it can indicate discomfort or nervousness as it is most frequently caused by gaze aversion. Eyes can also assume an inviting softer, squintier, more almond‐shaped appearance, which can be accompanied by a wrinkled brow.

Ears are varied in natural presentation and carriage. Some are permanently pricked, while others droop to the side. Ear carriage is best evaluated by looking at the base of the ear, and the pinna—the external part of the ear—can be assessed from “maximally backwards” to “maximally forward” (Schilder and van der Borg 2004). Even in long‐eared breeds like basset hounds, “ears back” can be noted by paying attention to the base. Ears pressed back are generally associated with greater levels of fear, submission, retreat, or even defensive aggression. Alternatively, ears forward suggest interest, attention, alert, or approach.

The body parts that contribute to dog visual communication merit discussion because people can have difficulty attending to actual in situ dog behavior (Tami and Gallagher 2009; Mariti et al. 2012). People often make assumptions and personality assessments about dogs based on appearance rather than behavior. In one study, an image of a yellow dog was rated as more agreeable, conscientious, and possessing emotional stability as compared to an image of the same dog with black fur (Fratkin and Baker 2013). Surgical procedures like tail docking and ear cropping can also affect personality attributions, and modified dogs have been perceived less positively—more aggressive and dominant, and less playful and attractive—than their natural counterparts (Mills et al. 2016). Awareness of the potential to make assessments based on appearance rather than behavior, coupled with an understanding of where to look for dog visual signals, can help people in their interactions with dogs.

Additionally, artificial selection and dog morphological diversity can impede social signaling and visual communication (Bradshaw and Rooney 2017). For example, brachycephalic dogs lack the highly flexible and expressive faces of more lupine‐type dogs, and hair or fur can prevent visible piloerection. Ultimately, some dogs may be physically unable to signal, or their signals may be difficult to notice, and dog behavior should be considered in light of what is physically possible for that dog.