By Sarah Su, Animal Science, ’24

Abstract

Companion animal species have multiple forms of communication, including tactile, visual, olfactory, and auditory signals. This paper will focus on vocal communication in canines, comparing the behaviors of wolves to that of dogs. As a result of domestication, most dog species show marked differences compared to the ancestral wolf in vocalization range, frequency, and function – wolves receive natural pressure to communicate with other wolves while humans have spent many generations artificially selecting for effective human-dog communication. This reflects the noise-related problems of dogs living in modern human society such as excessive barking and noise-triggered howling. Thus, understanding vocal communication in dogs (and its origins) is key to implementing solutions such as proper socialization, counterconditioning, and desensitization. 

Introduction

Vocalization as a communication behavior is especially distinctive in the canidae family, which includes dogs, wolves, jackals, foxes and coyotes. Wild canids can produce a variety of sounds including yelps, woofs/coughs, yips, screams, barks, growls, coos, howls, mews, grunts, and clicks [1]. The vocalization range of the domestic dog is similar, including: barks, howls, growls, whines, yelp, snores, groans, and grunts [2]. Of these, the quieter sounds are often used in casual contexts while the louder vocalizations can be utilized for more aggressive communication [3]. Though vocalizing is a universally observed trait in the canid family, the use of these vocalizations differ across species:, it was found that the domestic dog communicates by barking more often than howling, in contrast to their closest relative, the wolf [1]. This difference can be explained by the process of domestication – choosing different selective pressures, emphasizing interspecies communication, and changing the dog’s space/territory [3]. This paper will focus specifically on the differences between howling and barking vocalizations, and how they differ between the domestic dog and their ancestral wolf species. Additionally, this paper will touch on the impact of loud noises made by the modern dog when living in densely populated areas.

Barking vs. Howling

The sounds of barking versus howling differ from each other in volume, length and function, to the point where non-canine species may distinguish between them as well. A “bark” is a series of “noisy loud bursts with a medium fundamental frequency of 150-2,000 Hz” [3]. On the other hand, howls are much more variable, defined as “high amplitude, long range extended calls (1–10 s long) often with undulating fundamental frequencies varying between 150 and 2,000 Hz” [1]. The duration of a bark is considerably shorter than a howl, but howls are meant to carry for longer distances. Another large difference between the vocalizations is that barking is usually directed at a specific target/aggressor, while howling is nondirectional [5]. Because of these differences, barking is louder at close range compared to howling. Also, wolf barks are different from dog barks: the wolf barks significantly less frequently, at a much lower pitch than the dog [2]. Finally, the context of barking behavior is also different – wolves only bark when they feel threatened (defending territory or exhibiting dominance) whereas dogs bark reactively to many different triggers [1-6]. The differences between the way dogs vocalize compared to wolves can be partially explained by the process of domestication, which will be discussed later.

Barking and Howling in Wolves

In general, vocalization is biologically influenced by body weight and age – a large and mature wolf will have a longer howl with a lower pitch compared to a smaller juvenile [4]. The same is true for barking; although wolves bark infrequently, the tone and pitch will vary based on the individual [4]. In terms of howling, the wolf developed this vocalization for long-distance communication, territorial signals, and to foster relationships within the pack. The primary reason that a wolf howls is for location-signaling, with the purpose of finding pack members or calling the whole pack to its location [3]. 

Howling is one of the most prominent and frequent behaviors performed by the wolf species. It is used by wolves specifically because it is the vocalization that travels the farthest with the least distortion, enabling an individual to quickly locate the source of the howl. Howls are unique to the individual, which allows wolves to locate specific members [3]. Wolves also howl to maintain their territorial boundaries. If a wolf discovers another pack trespassing, it will assess the situation and either silently avoid the other individual or begin howling to call members of its own pack [3]. Finally, howling behavior is linked to temporal changes – wolves are apt to howl both night and day, but they are specifically more vocal between July-October, when packs are raising pups [7]. These months are also the period of least aggression between different packs, hence howling will be used for the purpose of locating individuals rather than calling the pack to a single location[7-8].

Barking and Howling in Dogs

Although domestic dogs have a similar range of vocalizations to the wolf, their dependency on humans due to domestication has resulted in neotenized communication behaviors. Neoteny, or hypertrophy, is the retention of juvenile traits of the ancestral species that is observed in a mature individual of the domesticated species. For example, wolf pups are born with short faces that elongate after adolescence, but dog breeds such as bulldogs, pugs, and boxers are bred for short and broad skulls that persist into adulthood (scientifically, this is termed as a “brachycephalic” head shape). This phenomenon extends to behavior: wolves typically perform play behaviors such as fetch when they are pups, yet humans have selected for dogs that play fetch past maturity. Indeed, breeds such as golden retrievers and labradors have been specifically bred to perform this behavior repeatedly. Hypertrophied behavior traits also exist in communication: mature domestic dogs vocalize loudly and frequently for care-giving, most commonly by barking, similarly to how wolf pups call for attention from their mother[9]. 

Studies suggest that domestication favors dogs that bark frequently because this vocalization is loud, repetitive, directional, and meant for those in close proximity. For example, Faragó, Townsend, & Range (2014) demonstrated that the shift from a pack structure to a human-controlled hierarchy resulted in a decrease in howling over time [3]. Unlike wolves, which occupy territories extending hundreds of acres, dogs living in houses don’t need to howl in order to be heard by a human – barking is effective at close range. Howling is primarily used by wolves because it is nondirectional and doesn’t require a response – barking is very directional and thus dogs imply a response from humans. Dogs also use barking for attention because the short/loud sound is more recognizable by humans. Humans are generally able to distinguish a dog’s mood by the sound of their bark – they are able to distinguish between aggressive, happy, fearful, and stressed barks in context [3]. Similar to wolves’ understanding of each other’s howls, humans listen to frequency, tonality, and rhythm to recognize a dog’s inner state of being [3]. As humans became the dog’s primary caregiver, their behavior shifted to communicating via barking, while wolves howl to communicate with other wolves. Another domestication-related reason for the prevalence of barking in dogs is the change in selective pressure. While the wolf is subject to the pressures of nature, dogs are subject to selection by humans. Barking is a hypertrophied trait – wolf pups and adult dogs bark – but excessive noise is detrimental to the survivability of an adult wolf. Since humans protect and feed dogs, there is no pressure to be silent in order to hide from predators or stalk prey [1]. Dogs are also more vocal than wolves because it makes them more trainable. Being loud and unable to survive in the wild creates a dependency on humans for food, which allows humans to leverage dog behavior. 

Another factor in canine vocalization is the social environment. A study in 2012 found that free-ranging or feral dogs living in packs bark only in context-specific situations (like wolves) while indoor dogs tend to bark at things indiscriminately [5]. In this case, the immediate environment is another factor in vocalization – as long as dogs are housed indoors they will bark more often than they howl. Another study found that when placed in unfamiliar environments, domesticated dogs made frequent contact-seeking sounds towards the experimenter, whereas wolves went completely silent. This is further evidence for genetic manipulation by humans for traits that would normally be selected against in the wild [1].

Dogs and Society

Barking allows humans to better understand dogs, and it may have been initially beneficial to the human caregiver that dogs bark louder and more continuously than wolves [9]. However, barking is also the noisiest vocalization and dogs have been genetically bred to bark excessively with little stimuli needed for continuous noise. This presents consequences in the modern-day for dogs living alongside humans in cities.

 Not all dogs are the same, and noisy barking tendencies may change based on the individual’s breed, size, or temperament, but the instinctual reasons for vocalization remain the same. Some breeds that are relatively quiet include Basenjis, Shar-Peis, and Chow-Chows [2]. In contrast, hound breeds are noisy because they were bred to vocalize – Transylvanian, Basset, Finnish hounds each perform a specific type of bark for hunting purposes [2]. These facts should be kept in mind for those looking to purchase or adopt a dog. Other causes of loud vocalizations in dogs are reactive howling and separation anxiety. It is relatively common for dogs to howl in response to high-pitched tones such as alarms, doorbells and loud/upbeat music, which are inaudible to humans but detectable by dogs [10]. Thus, it would be prudent for potential dog-owners to take into account where they are living when considering their ideal companion – if they live near a busy highway, a fire department/police station, a neighbor who plays percussion instruments, etc. Meanwhile, separation anxiety is termed by the American Kennel Club (AKC) as “when your dog exhibits extreme stress from the time you leave him alone until you return;” it includes behaviors such as destroying items, pacing, urinating/defecating, and vocalizing loudly [11]. Separation anxiety can be alleviated through retraining, which is elaborated on in the next paragraph. 

Given that the primary function of barking is to catch human attention, the most effective solution to barking is counterconditioning and desensitization. Counterconditioning is conditioning against a specific behavior while desensitization is the act of exposing an individual to a trigger until they do not react to it anymore [12]. These techniques were primarily developed to combat separation anxiety, which is characterized by destructive behaviors, restlessness, and persistent/continuous vocalization. Desensitization is also used to train reactive dogs, dogs that either run towards a stimulus or bark incessantly at it. In the case of stimuli-triggered vocalizations, desensitization would involve exposing the individual to increasing amounts of the trigger, which increases the dog’s threshold to react until the dog no longer reacts to the stimuli (stops howling/barking). For counterconditioning, the ASPCA advises the following steps to resolve excessive barking issues: (1) ignore noise, reward dog for being quiet, (2) treat attention as a type of reward (3) train “speak” and “hush” commands, and (4) spend time with dog, as they may be barking because they have not been exercised enough or because their social needs have not been met [12]. By rewarding silence and/or increasing tolerance, human owners can “counter” the domestic dog’s instinct to be noisy. 

In summary, human selection has led to dogs developing louder and more dependent vocalizations compared to their ancestral counterparts. This tendency towards loud attention-seeking enables dog owners to better understand their pet’s needs, but it can also backfire when humans and dogs live in close range. The balance lies between every dog’s genetic predisposition to be loud and the human caretaker’s responsibility to adequately discipline their pet.

For wolves living in the wild, howling is used for long-distance communication, territory signaling, and to foster bonds between individuals in the same pack .

References:

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