ReviewBarking in family dogs: An ethological approach
Introduction
The casual human observer is often inclined to assume that certain animal actions have a communicative role but ethologists interested in the natural behaviour pattern of animals use a complex methodology to identify action patterns as communicative signals. There is, however, a general agreement that animal signals should provide the sender (or both the sender and the receiver) with some sort of advantage. In addition there should be indications that the behaviour has evolved to fulfil a signalling function (Krebs and Davis, 1993).
Ethological theories emphasise the role of ritualisation in the genesis (evolution) of signals (Smith, 1977; but see also Hauser, 1996). Accordingly, most signals have evolved from behaviour actions that closely affected survival and are associated with biological (physiological) controlling processes. For example, Andrew (1962) proposed that the facial and vocal signals associated with fear might have originated from behavioural responses aimed at protecting the individual from noxious stimuli. Such actions include closing the eyes, lowering the eyebrows and flattening the ears. In addition, rapid closing or narrowing of the glottis may have been associated with the production of some noise (vocalisation) that provided the ‘raw’ material for the evolution of vocal signals. If there is a behaviour pattern for evolution to act on then the ritualisation process is likely to have led to changes that distinguish behaviour signals from general patterns of behaviour, so making the signal less ambiguous. Such behavioural (vocal) actions become more exaggerated, repetitive and stereotyped.
Other theories place more emphasis on the observed correlation between the sender’s advantageous (adaptive) traits and the features of the signal. Comparing the vocalisation of many mammalian and avian species, Morton (1977) argued that acoustic structure might basically reflect a correlation between body size and sound frequency, based on the physical rule that larger bodies produce sounds that are characterised by lower frequencies and a wider band range. In this case, the quality of the signal would in some way predict the physical qualities of the sender that (in the long run) could be advantageous for both the sender and the receiver.
Other selective forces on the part of the receiver may also influence the form of the signal (see, for example, Guilford and Dawkins, 1991). Owren and Rendall (1997) assumed that during evolution the sender’s ability to form special signals was influenced by the effect the signals had on the receiver. McConnell (1990) found that young herding dogs could be more easily trained to go to the trainer when short, rising frequency sounds were used instead of long, descending ones. Examining the acoustic signals used by shepherds from very different geographic regions, it was found that dogs can be encouraged to work with short, high pitched whistles whereas they are stopped by long, descending whistles (McConnell and Baylis, 1985). Although whistling shepherds have appeared relatively recently in the evolutionary history of the dog, their acoustic signals most probably exploit the dogs’ inherited preference to respond in a certain way to acoustic stimulation. The studies by McConnell and Baylis (1985) showed that simple and well described acoustic rules work uniformly in the case of human–dog vocal communication.
Although in many cases the primary form of the signal is under strong genetic control and there is little need for experience on the part of the sender, the amount of learning depends on the species and the context in which the signal is used. Janik and Slater (2000) distinguished between learning the signal (or about it) and learning the context in which the signal was effective. No such data are currently available on acoustic signalling, but with visual signalling there is some evidence that although wolves do not need to be exposed to conspecifics to be able to show certain forms of species-specific agonistic signals, they do need to learn about the use of the signals and also how to react to the signals of group members (Ginsburg, 1975).
Joint adjustment in communicative signalling between interacting group members has been described as ontogenetic ritualisation (Tomasello et al., 1994). In this case, not only species-specific signals but other patterns of behaviour could increase communicative function through learning on the part of both the sender and receiver. This process can play an important role in interspecies communication systems when signals in different species might well have different evolutionary origins, and its effectiveness may depend on whether the receivers can learn about the signal and the senders can to adjust their signalling behaviour to the constraints of the receiver.
In this review we use the ethological concept of animal communication to the functional-contextual analysis of dog barks. Recent research has shown that barking might have been under selected and (1) may have been modified according to the so-called motivational-structural rules of vocal communication in mammals (Morton, 1977), (2) may play a role in human–dog communication (and possibly also in dog–dog communication), and (3) is affected by learning through the process of ontogenetic ritualisation (Tomasello et al., 1994). Thus, there is a possibility that barking has been acquired and is used in a novel function in dogs in comparison to the ancestral species.
Section snippets
Barking and the vocal repertoire of canids
Domestic dogs, like their closest wild relatives (wolves, jackals and foxes), have a rich vocal repertoire. They vocalise in a wide variety of social contexts and this behaviour undergoes considerable alteration during development (Tembrock, 1976). Early studies on dog vocalisation focused mainly on the formal (physical) description and categorisation of the different kind of acoustic signals (Bleicher, 1963), but subsequent comparative approaches have concentrated more on functional aspects (
Dog barking
Although there has been no scientific investigation on the breed differences of barking, we know that some breeds do not (or only rarely) show any propensity to bark (for example, the Basenji, Chow–chow, Shar-pei), whereas others bark excessively. In the case of the latter, some breeds were probably selected for a specific kind of barking, such as various types of hounds that are bred to follow the trail of game. The importance of characteristic forms of barking is even mentioned in some dog
The possible function of dog barking: Inter- and intra-specific communication
When investigating a behavioural feature of any species ethologists are keen to find the functional significance of the trait. Without much experimentation or systematic work some researchers have argued that barking may have been a by product of domestication and so lacks any functional value (Coppinger and Feinstein, 1991), whilst others have underlined the selective role of the human environment (Feddersen-Petersen, 2000). Below we present some evidence to support claims of the latter type
Possible veterinary implications of barking
The most common cases leading to concerns about an animal’s health are (1) excessive barking (separation anxiety; see, for example, Sherman and Mills, 2008); (2) bark prevention (i.e. antibark collars and ‘de-barking’ with surgery of the vocal cords where too much barking was considered as a nuisance; see, for example, Steiss et al., 2007); and (3) barking as a possible indicator of animal welfare in dog shelters (for example, Sales et al., 1997). In general, the quality of barking is not an
Conclusions
It is apparent that (1) dog barking shows context-specific acoustic features, (2) humans from different age groups and with different amounts of dog-experience can recognise the context within which a dog is barking, and (3) humans are able to attribute basic inner states to barking with particular acoustic features. In addition, acoustic differences when barking is recorded in different contexts seem to follow the motivational–structural rules described by Morton (1977). These results
Conflict of interest statement
None of the authors of this paper has a financial or personal relationship with other people or organisations that could inappropriately influence or bias the content of the paper.
Acknowledgements
This study was supported by the Hungarian Scientific Research Fund (OTKA) Grants No. T047235 and T049615, the Hungarian Ministry of Education and the EU FP7-ICT-2007 LIREC-215554.
References (49)
- et al.
Vocalisation in wild canids and possible effects of domestication
Behavioural Processes
(1976) - et al.
Barking foxes, Alopex lagopus: field experiments in individual recognition in a territorial mammal
Animal Behaviour
(2003) - et al.
Receiver psychology and the evolution of animal signals
Animal Behaviour
(1991) - et al.
The different roles of social learning in vocal communication
Animal Behaviour
(2000) - et al.
Assessment and treatment of excessive barking in the domestic dog
Veterinary Clinics of North America: Small Animal Practice
(1997) Coyote vocalisations: a lexicon and comparisons with other canids
Animal Behaviour
(1978)- et al.
Recognition of emotions in macaque vocalisations by children and adults
Language and Communication
(1994) - et al.
Dogs can discriminate barks from different situations
Applied Animal Behaviour Science
(2008) Acoustic structure and receiver response in domestic dogs, Canis familiaris
Animal Behaviour
(1990)- et al.
Can humans discriminate between dogs on the base of the acoustic parameters of barks?
Behavioural Processes
(2006)
Acoustic parameters of dog barks carry emotional information for humans
Applied Animal Behaviour Science
Noise in dog kennelling: is barking a welfare problem for dogs?
Applied Animal Behaviour Science
Canine anxieties and phobias: an update on separation anxiety and noise aversions
Veterinary Clinics of North America, Small Animal Practice
Evaluation of plasma cortisol levels and behaviour in dogs wearing bark control collars
Applied Animal Behaviour Science
Canid vocalisations
Behavioural Processes
Barking in domestic dogs: context specificity and individual identification
Animal Behaviour
Size and shape in ontogeny and Philogeny. Paleobiology
The origin and evolution of the calls and facial expressions of the primates
Behaviour
Physical and behavioural analysis of dog vocalisations
American Journal of Veterinary Research
Comparative social ecology of feral dogs and wolves
Ethology Ecology and Evolution
Hark! Hark! The dogs do bark… A new theory on why dogs bark
Smithsonian
Spectral analysis of neonatal wolf Canis lupus vocalisations
Bioacoustics
Vocalisation of European wolves (Canis lupus lupus L.) and various dog breeds (Canis lupus f. familiaris)
Archiv für Tierzucht
Hunde und ihre Menschen
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