Any terms to be used to describe aggressive-behaviour in the domestic dog, Canis lupus familiaris, should be universally understood and accepted for legislationand treatment methodology. Ethological comparisons between wolves and feral dogs reveal the wolf hierarchal-structure and alpha male-female reproductive system is not shared by domesticated dogs. However, the unique genetic plasticity of feral and domestic dogs provides a possible explanation for differences.
It has been suggested that the term ‘dominance’ in domestic dogs should be replaced with Resource Holding Potential (RHP) and Resource Value (RV) as a model to describe the motivation for intraspecific aggressive-behaviour and interspecific-aggression. RHP models the behaviour of aggressive risk-taking in domesticated dogs. However, this system model may not take into consideration the unique dynamic of human-dog interrelationship, dysfunctional socialisation and mixed inter-species communication confusion. Owner-influences, in terms of handling and emotional-interpretation and interaction, need to be considered alongside known triggers and reinforcement for undesirable behaviour in dogs.
The author proposes that while the term ‘dominance’ remains useful to describe dogs that aggressively challenge owners, RHP-related aggression is proposed as a potential term to describe competitive, intraspecific and, in particular, possessive-aggression in domestic dogs. Introducing the term RHP-related aggression should not conflict with status-reduction programs that include discipline-training and structured dog to owner interaction-control which is currently in use in to reduce aggression.
KEY WORDS: domestic dog; dominance-aggression; RHP-related aggression; resource holding potential; competition; status; aggressive competitive-behaviour
Bradshaw et al (2009) put forward the case that the term dominant is not applicable when describing aggressive behaviour in domestic dogs.
In place of dominance, they suggest that dogs interacting aggressively a best described through a model system of competition known as Parker’s Resource Holding Potential, Parker (1974). This term is used to describe when an individual animal appears willing, or more daring, to risk injury to gain a resource value or advantage. The competing animal then enters into a fight or escalates aggression in order to win a contest. The motivation is said to depend on the value of the resource (RV) or what is eventually won in the outcome.
Bradshaw et al and others suggest the application of Parker’s resource holding potential (RHP) and subjective resource value (RV) as an alternative system to dominance to help explain un-established relationships between competitors such as dogs.
RHP has been most widely applied in ichthyology and aquatic crustacean-related ethology and has been used in many species to explain, for example, fighting behaviour in cichlids, hermit crabs or sand gobies.
It is common knowledge that many cichlid species, for example, are highly aggressive and have evolved complex conspecific strategies during the relatively short period of geological time. Cichlid species are known to fiercely compete over extremely limited spaces and for mate-choice in a lake or river shoreline boulder-strewn territory. They rarely shoal passively unless juvenile and come together during pair-spawning and subsequently pair-bond to guard and protect eggs and free-swimming fry, behaving in the same way as ancestral ocean reef fishes, such as gobies, damsels and clown fishes, which also pair off for reproduction.
These species compete with conspecifics and other species for the ‘rights’ to the occupation of sand burrows, crevices or corals or for the occupancy of anemones in which some species form a symbiotic relationship. How the competitive aggression behaviour within a limited-territory and linked to reproduction in aquatic species can be compared to aggression observed in domestic dogs requires examination. Studies of free roaming (250 km²) feral dogs in central Italy, Boitani et al (1995) describes packs operating in a relatively large scale territory. The RHP model may provide a logical strategy that helps to explain animal competition in a reduced territory, (home ‘arena scenario’), over resources. This is because most homes represent a reduced territory for dogs. However, when dogs are moved from a home territory by owners or placed into rescue centres it would be highly likely that these changes might be an important factor in influencing aggressive conflicts. Episodes of interspecific aggression, that occur between dogs previously socialised together in the same home, can be triggered by a dispute over a resource (own unpublished findings, appendix 2). This is particularly applicable when adult , unsocialised dogs (rehomed or brought together by house-sharing partners) are constrained together into one household.
The RV or the potential gain (protect or possess) in these novel, and therefore competitive situations, may be assessed by some dogs as worth the risk of injury that could result from aggression.
The challenge for the use of the term dominant in dogs has raised a number of questions from the perspective of practitioner dog behaviourists. Experienced professionals, assessing dogs on a regular basis, usually develop an understanding of how the combination of traits, socialisation and breed-predisposition significantly influences domestic dog behaviour. The terms dominant and dominance have been in use for over a century in association with dog behaviour to describe a dog that challenges owner-authority. This usage is based on the idea that such an owner- challenging dog is attempting to attain a higher status in a hierarchical sense.
In generalisation of behaviour, dog temperament ranges submissive or passive to ‘dominant’ in current usage of the terms. The majority of dogs possess a disposition which could be described as biddable, relaxed and friendly and so might fit in the middle of this scale. As companion animals, socialised dogs have a tendency to want nothing more than to associate with a familiar circle of family and their friends. These dogs are content to share a ‘home life’ or social group that might be considered a ‘replacement-pack’. The ‘kill’ in domestic day to day life will originate from the supermarket or pet shop and any ‘hunting and foraging’ mode of behaviour is most likely to be a replacement-activity expressed through walks. With food and exercise, these dogs need only social interaction and a comfortable resting position in the home.
Dogs that have been re-homed, by rescue centres or privately between owners, can be described as ‘insecure’ or unsure of their social positioning within a home. They may have a temperament that could be described as submissive or challenging. In a behavioural sense, these dogs differ from normally socialised puppies which have been born to a relaxed and friendly litter-mother and purchased from an experienced or professional breeder. Rehomed puppies and dogs are more likely display temperaments that are extreme. This may mean they are more likely to display hyperactive or aggressive behaviours or be submissive and withdrawn, Wells and Hepper (2000).
Although any dog can display hyperactive or fear-response aggression and owner-attachment conditions, it is rescue and re-homed dogs that appear more likely to develop unwanted behaviours such as fear and aggression of strangers or other dogs and over-dependency on owners. The condition known as dog separation-related disorder (erroneously referred to as separation-anxiety, a diagnostic term mainly used in child psychology) is recognised by many professionals and veterinarians as most commonly presented by rescue and re-homed dogs. Dog separation-related disorder (Appendix 1) is a condition where over-reliance on the presence of on an owner triggers a dog to present a range of stress-related behaviours when an owner is absent.
Breed types and individual temperament, and the terms ‘submissive’ or ‘dominant’ are widely used in behavioural analysis when assessing temperament in companion dogs. There is a need to address this common usage in order to make clear why it may have to change. Aggression in domestic dogs and the potential use of aggressive breeds as weapons is in the forefront of popular media. The need to review any significant changes in the description of aggression in relation to domestic dogs is now pressing because owner responsibility is being increased in legislation.
A wolf subspecies in the home
The domesticated dog, Canis lupus familiaris, is classified as a sub-species to the Grey Wolf, Canis lupus lupus. However, it has bee put forward that domesticated dogs do not share the same hierarchical rigidity and associated behaviours with their close lupine relative. Research indicates that feral packs of dogs do not display a fixed pack-structure which has been observed in wolves. Bradshaw et al (2009) discuss why this difference might be important in understanding the behaviour of the domestic dog and how early research in captive wolf packs may have distorted 20th century ethological opinion. Referring to improved techniques for observing the behaviour of wild wolf packs, which have led to a reappraisal of the basis of their sociality, they quote the research of Mech and Boitani (2003), ‘ .. the basis for the social unit of a wolf population is the mated pair’ and it is noted that ‘the alpha pair are reported to be accompanied by their off-spring from previous years and that dominance contests are rare’.
They cite this observation of reduced conflict in a recent wolf study which may well be a true reflection of the kind of social stability that, in analogy, could be compared to the social stability most dogs experience in domestication.
Conflicting evidence that the dog, domestic, feral and their wolf relatives, may or may not share an innate hierarchical structure will be continually debated. Bradshaw et al (2009) acknowledge that the lack of observations that would suggest obvious co-operation in their cited feral dog studies may be a direct result of, quote: ‘repeated interference and displacement by man’. The need for a fixed hierarchical structure may have reduced in the feral dog. Taking this particular observation to its logical next stage, In terms of the behaviour of domesticated dogs, it is highly likely that the need for a fixed hierarchical structure has been reduced even further by man’s intervention.
What has been established in categories of aggression, is that the asymmetry of conflict can be influenced by a number of variable, internal and external, factors, Maynard-Smith and Parker (1976).
In domestic dogs it is necessary to consider that the most common arrangement is for owners to keep one or two dogs in the home rather than a group. On occasions when groups of domestic dogs are maintained together, excluding examples such as hound packs that experience an extended period of socialisation, many owners is able to point out the so-called ‘dominant individuals’. In a group of approximately 20 adult, Border Collies of various ages, two bitches were described to me by the owner to be ‘dominant individuals’.
When the group were exercising together on an open sloping field, with Frisbees thrown, these individuals successfully retrieved while the other dogs appeared to defer to them (personal observation). In this albeit anecdotal observation, the question asked is: in terms of the Resource Holding Potential, were the two dogs more willing to risk aggression when competing for the RV (ie Frisbee) or in this large group of domesticated dogs? When the majority of dogs deferred to two individuals this showed they were less willing to compete against them for the resource. indicates a hierarchical structure and alpha-like status.
A factor to be considered when comparing social structures in domesticated dogs and the wolf is that the ancestor lineage between them is not clearly defined. This is because of complexity of influences, including continental origin (European, African, Arctic, Asian and North American species), together with thousands of years of human intervention and subsequent high frequency and variability caused by intensive line breeding in addition to Interbreeding with other dogs such as the Coyote, Dhole, Jackals and Foxes. These species may be part of the lineage to domestic dogs and have been frequently observed as individuals or in territorial breeding pairs. This variance from pack structure could have a significant bearing as to why a rigid hierarchical system has not been recorded in feral dogs or in domestic dogs.
Both the intervention and migration of man has influenced the reproductive lineage of dogs. When the option is available almost all species breed amongst conspecifics. However, when geological barriers are artificially broken, a species-specific mechanism, that would normally prevent fertile hybrid offspring, is often lacking.
In human recent history, in terms of thousands of years, one or more species of dogs were domesticated. How domestication, in particular a loss of fear of man, could be achieved was revealed following a review of the extended breeding dog programs known, Hare et al (2005). This review, based on a population of captive Russian foxes that had experienced 45 years of selective-breeding, revealed important aspects of domestication and provides important behaviour clues about how the tame dog we know today first came into being. These findings are based on the descendants of Russian foxes first in kept in a Siberian research centre from 1959.
During the breeding program, individual juveniles were identified early by Russian geneticist Dmitry Belyaev for their willingness to show a lack of fear and aggression when first exposed to humans who were feeding and interacting with them. Only these particular foxes displayed an eagerness to accept human contact and, instrumental in behavioural terms, an ability to be able to read human facial gestures. These individual foxes were then selected for breeding and were subsequently proved to be able to successfully pass significant intelligence tests based on finding hidden food by obtaining guidance through the pointing gestures of handlers.
This research, gathered over such a significant period of time, indicates that it is more likely that the gene for a ‘lack of fear’, together with innate sociability (common in groups of animals), which has facilitated the domestication of wild dogs. The domestic dog may not share the wolf’s need for a strict social structure but of far greater importance is to acknowledge that some large breeds are capable of displaying predatory-aggression and are powerful enough to kill an adult person. The antisocial ‘aggressive dog’ temperament is frequently the result of poor breeding including an interrupted socialisation and breed trait. Other influences on unwanted behaviour in domestic dogs include when they have been maintained under an inadequate or poor diet and an impoverished environment with the lack of human and social interaction. This aetiolgy excludes where breeds have been trained or encouraged to be guard dogs. There is also the potential influence of faulty-learning when juveniles are maintained alongside aggressive animals from an early age or when there has been the experience of attack by another animal or abuse by people. Here, the influence of learned behaviour can result in a dog developing fearful or aggressive tendencies. This is particularly evident in those dogs that already been selected for traits such as non-retrieval predatory-hunting, fighting, guarding and livestock-control.
There are additional influences that can potentially contribute to the development of the eventual mature companion dog temperament. These include litter-mother temperament, the nutritional level of diet and social development linked to the age removed from the litter-mother, Gazzano, et al (2008). Other variable influences on temperament include physical health, life experience and genetics which could prove to be most significant as we learn more about how aspects of behaviour can be directly transferred through generations. Finally, the narrow ‘gene pool’ known to exist in some breeds increases the chance of genetic drift where physical where physical and psychological defects are more likely to occur. These include hip and elbow displasia, patellar luxation and Legg-Calve-Perthes and results in them becoming more common place. These physiological conditions can lead to long-term chronic pain which, in turn, will significantly influence the temperament of some dogs.
Interpretation of antisocial behaviours displayed by dogs
Owners may only review the behaviour of their dogs when it becomes necessary or at the point where urgent action is required. This is when antisocial episodes, including owner-separation signs (Appendix 1) or aggression, are being displayed (Appendix 2) and where professional advice is sought for potential treatment. In some instances, re-homing or euthanasia options are considered alongside behaviour treatment.
Some alterations to normal behaviour in domestic dogs manifest in casual changes. Dogs displaying owner-separation behaviour, for example, may present early signs of a developing an unhealthy owner-attachment in terms of over-dependency which begins with ‘shadowing’ family members from room to room around the home and including the bathroom and bedroom. There can be increasing levels of hyperactivity exhibited when the dog is reunited with family members after being alone and some may submissively urinate during threshold greetings. These displays can be a sign of a developing condition, separation-related disorder, and appeasement behaviour. Owner interpretations of such behaviours vary but many report that such displays represent faithfulness.
Communication between owner and dog can cause different reactions in a dog. A voice-tone of an owner who is ‘frustrated’ or angry might be met by a submissive dog with a head down, tail between the legs, posture. It would not be unusual for such dogs to retreat behind a sofa, to hide under furniture or to seek out a refuge in the dog bed. The terms submissive or subdominant, insecure or fearful, are used by veterinarians, dog trainers and behaviourists to describe this type of dog temperament.
The ‘dominant dog’, sometimes referred to as ‘challenging’ in dog training, contrasts in temperament and will often display unwanted behaviours from an early age which can include antisocial or aggressive tendencies. These behaviours become progressive unless some form of status-reduction program and early obedience training is put into place. A dog with this type of temperament usually obtains owner-attention on demand. Challenging behaviour can be observed through the dog’s stubbornness and an increasing refusal to respond to an owner’s verbal instructions. This scenario includes dogs that are challenging, either by refusal or aggressiveness, instructions to come off furniture. During play and exercise sessions, the ‘challenging dog’ can refuse to give up a ball or will ignore a name-call (selective hearing) when instructed to return to an owner. This developing challenging temperament can become progressively worse and so increasingly difficult for the owner to gain control of the dog. Those dogs displaying this type of challenging behaviour (the ‘aggressive dog’) can take the form of a growl or a fixed stare (anthropomorphic maybe but this is perhaps the dog equivalent of insolence).
In some scenarios, the ‘challenging dog’ expresses possessive-aggressive behaviours towards the owner, family members or to other dogs. In general terms, an aggressive episode might include barking, growling, snarling or biting and would involve resources such as food-items, toys and territory area. In personal observations, the dog presenting these behaviours will frequently take up specific positions or elevation in the home. These include lying across thresholds and seeking out elevated positions on furniture and stairs. Owners interpret this dog temperament as ‘bossy’, ‘bold’ or ‘aloof’ or a number of other similar terms that are subjective and certainly anthropomorphic.
The term ‘dominant dog’, when used by the majority of dog trainers and professional practitioners, is meant to describe those dogs that are challenging against any form of control from owners in these ways. In many instances such dogs may not have received consistent control from owners. There can also instances where family members defer to the dog in a passive sense and use avoidance instead of trying to change the behaviour not wanting to be confrontational.
Owners that humanise companion dogs frequently project their ideas and mental capabilities onto them. This aspect of a mutual interspecies relationship should be considered natural because to owners their dogs represent an important family member to them. In these instances, the relationship when humanised means the dog becomes the replacement-companion, child-replacement, friend or even partner-replacement. Interspecies communication barriers excuse some antisocial or unwanted behaviour exhibited by challenging dogs. Hyperactivity, continual and repeated-vocalisation and attention-demanding are the most frequently recognised unwanted displays by these dogs. An analogy might be the infant addressing its parents with the challenge, ‘You’re not the boss of me!’.
The ‘challenging dog’ cannot articulate such a verbal challenge but many antisocial dog personalities might be compared to ‘Attention-Deficit Hyperactive Disorder’ children. It is common for these dogs to express a range of dog behaviours including displaced sexual-mounting, mouthing, controlling, challenging and inappropriate protecting aggression for family members. The potential for any confusion and structure and boundary, from the dog’s perspective, is highly likely to be caused because challenging dogs are often able to dictate the commencement and cessation of any interaction. This gives a dog an element of control over owners or people within the family-dog ‘social-group’. ‘Challenging-behaviour’, particularly when observed in young dogs, can be associated with increasing signs of ‘disobedience’. Signs might include a refusal to respond to owner lead-control on walks; lunging, hyperactivity or aggressiveness, hyperactivity of aggression when travelling in vehicles and most commonly, refusal to recall following an owner-initiated name-calling.
There are associated influences related to such behaviours, exuding physiological causes, such as negative vehicle-association and experience, breed type and whether there has been either limited or non existent training. The ‘challenging dog’ does not always exhibit an aggressive temperament (Appendix 3b and 4b). When unsure of owner authority, and this can be the result of a lack of control or training, incorrect handling or inconsistency, these dogs might display hyperactive behaviour on the arrival of house-visitors or returning family members. In such a mode of behaviour, it is not uncommon for these dogs to display unwanted responses such as jumping up, clawing, mouthing or repeatedly barking. The same dog exhibiting these behaviours can often be observed competing for attention with owners during a range of everyday social activities including during telephone conversations and discussions.However, a refusal to conform to how the majority of owners expect a companion dog to behave can be acceptable to some.
The term ‘dominant’ is widely recognised by those assessing aggressive dogs that are frequently displaying challenging-aggression and, in extreme instances, subsequently bite their owners or family members. In recent years, the term ‘dominant’ has been used less frequently by professional who are more likely to refer to aggressive ‘challenging behaviour’ in a dog as a ‘status-related’ even though both terms allude the same dog temperament. In order to reduce such aggression there is no known alternative system to status-reduction programs currently available apart from euthanasia; at least not one in terms of humane methods.
The most commonly used status-reduction program is currently based on projecting owner leadership to the dog, a strategy of interaction-control, activity-structure and applying boundaries in the home and during walk environments. Leadership-style interaction has achieved success when promoted by owners that offering dogs consistent instructions which can be learned quickly through the use of conditioned sound signals. These are used alongside disciplined training using ‘rewards’ as positive reinforcement (most commonly through classical conditioning with clicker training for example) or negative punishment (the removal of reward with Training discs for example) for shaping behaviour in the operant sense.
The fearful or withdrawn dog may also display aggression and can also behave in a challenging way. However, this temperament, frequently a working breed or cross breed, is often in an hyper-alert state or vigilant which results in a situation where another animal, a noise or object forces an adrenaline-driven, fight or flight, response. Many dogs suffering from a hyper-alert condition can be observed to initially display a fear response, vocalised through target-barking (warning) and subsequently a ‘flight response’ is presented. This response can be in reaction to unusual noises, fireworks, low-flying aircraft, hot-air balloon burners and industrial sounds not previously encountered. However, a fear-response can also be triggered by noises associated with everyday activities including the sound of household equipment and a wide range of stimuli. In these dogs, the ‘flight outcome’ or response is escape and in this mode of behaviour they will might race to return home or return to the vehicle. Some dogs are known to cover great distances that results in them becoming disorientated and then lost. The ‘fight outcome’ is frequently expressed as fear-based aggression (Appendix 3a and 4a).
The term dominance has widespread use throughout animal behaviour science. The text book definition records that it is used to describe ‘a feature – within a social organisation – of an individual displaying aggression to acquire a high status over another that retains a lower status’.
The principle of a status-structure within a group was first described a century ago as a result of observations involving flocks of domestic fowl. The term ‘pecking order’ came from this study but hierarchical relationships in social groups are known to be widespread across the animal kingdom. However, the terms dominant, dominance and dominate are easily interchangeable and open to interpretation. Dominance hierarchy is used to describe a ranking order in a social group of animals that provides potential stability when there is competition for resources which need to be shared.
The term ‘dominance’, when used in relation to aggression studies in domestic dogs, is interpreted by veterinarians and animal behaviour practitioners to have a different meaning. It is generally used to describe a dog which is directing aggression towards an owner or another dog that is not already displaying aggression towards it.
Acts of aggression observed in dogs can be triggered as a challenge to owners but are often associated with resources such as food and food-related items, toys and access to people (Appendix 4b). Maternal aggression seen in whelping bitches is deliberately not discussed or included here.
Bradshaw and Nott (1995) discussed the development of dominance in dogs. They make reference to its development in juveniles: ‘Behaviour that is recognisably competitive which might be involved in the establishment of dominance, first appears in when the pups were about three or four weeks old’.
Experienced breeders acquire a knowledge and understanding of developing puppy trait. The term ‘strongly competitive’ when used while observing litter-siblings strength-testing each other is possibly more relevant than the term dominance. A recent study, based on the behavioural analysis of over 700 dogs, describes dominance-aggression and suggest that the behaviour is expressed primarily as possessive-aggression. Perez-Guisado and Munoz-Serrano (2009) located pedigree and cross breeds, perhaps significantly, through an ‘opportunist method’ of approaching owners whilst walking with their dogs. This chance system of selection for the study group, rather than the use of dogs already being assessed for aggression, means the study group offered them a general overview of this form of dog behaviour. The study group came from 5 cities in Spain and included an almost equal number of dogs and bitches.
The conclusion of this research is that the greatest influence on dominance aggression in dogs is in owner-related factors such as whether obedience training had been undertaken; if only vocal punishment was used (lack of any physical method) and how much time walking and the total time owner and dog spent together. Whilst there may be a variance caused by cultural differences, it was suggested that older people are more responsible and spend more time with their dogs to enforce control.
In a section, Social behaviour of neutered dogs, Bradshaw et al (2009) introduced an unpublished study of 19 neutered male dogs maintained within a rehoming charity (rescue centre). Bradshaw, Cooke, Robertson and Browne (the authors of this unpublished study) report that, even among 8 dogs which interacted the most, ‘no clear cut dominance hierarchy could be distinguished’.
This research can be questioned, firstly, from the opening statement which reads: ‘Since aggression between companion dogs is not restricted to sexually entire individuals, the wolf pack dominance structure would have to apply to neutered dogs to explain dog-dog aggression within households’, raises an immediate question. Unless there is a study based on neutered wolves in the wild any such ethological comparison would appear to be entirely speculative. Secondly, these observations are highly likely to be distorted not only by the fluctuating psychological states of dogs confined within a rescue centre but also by the influence of significant asymmetry that would exist in one-to-one conflicts. Potential asymmetry on a significant scale would include territorial uncertainty and the breed or cross breed size range of the dogs involved in the group study.
The logic of asymmetric contests was first pioneered in Maynard Smith and Parker (1976). The various significant roles in, mainly, asymmetric animal contests and their predicted outcome including the result of contests between fighting animals depend much on the rate that information is acquired. This, in turn, is known to be relative to the rate at which costs are expended, and on whether contests normally escalate in intensity, remain at the same level or de-escalate as detailed in Parker and Rubenstein (1981).
Until further information is provided on the unpublished study, including dog breeds, sizes, ages and gender and how long they had been maintained in the rescue centre and exercised together, it is impossible to consider asymmetric influences in respect of this research. In addition, the results presented would be extremely difficult to test statistically or to replicate.
According to information, provided in recent communications, Bradshaw (pers.comm) explained that some of the dogs had been held at the rescue centre for at least 6 months and that 12 of the 19 dogs had been held there for 5 years. These dogs were undoubtedly disassociated from what would have been their original social groups of former owners, family members or friends. With some dogs, the prior to rescue, a social life may have included other dogs with which relationships would have been established. Such relationships may have been successful in terms of socialisation but equally there may have been scenarios where individual dogs had been exposed to ongoing conflicts and agnostic episodes involving other dogs and people.
In a parallel to the experiences of foster children, but without suggesting a comparison of human complexity, all the dogs in this study would be both socially and territorially disorientated. They would most likely be exposed to – or be in close proximity with – dogs in a distressed condition. In these situations, dogs being viewed or brought in to the centre, as well as those dogs already boarded that would be suffering from owner-related separation-related disorder, would be vocalising stress through repeated barking, whining or howling. This scenario, common to all rescue centres, increases the level of abnormality represented in this study.
Wells and Hepper (2000) reported in, Prevalence of behaviour, problems reported by owners of dogs purchased from an animal rescue shelter, that, out of 556 responses to their survey, 68.3% reported that their dog exhibited a behavioural problem and the most common being fearfulness and that dogs displaying aggressiveness were more likely to be returned to the shelter. More so, in fact, than those dogs displaying coprophagy or inappropriate elimination which suggests aggressiveness is a significant behaviour factor when owners decide to reject a rescue dog. This particular factor could have had a significant bearing on determining which type of dog temperaments were available for the Bradshaw et al study.
In a human parallel of social dysfunction (and its lasting effect on antisocial behaviour) research on young human males and aggressive behaviour, Dmitrieva et al (2001), indicated that a high percentage of individuals displaying antisocial behaviour had experienced a disrupted or dysfunctional family. They examined human males displaying conduct disorder and the findings revealed these individuals possess higher than normal circulating levels of hormones from adrenal cortex, gonadal and growth-hormone axes which are associated with stress, aggression and development.
Increased hormonal activity and its influence on aggressive behaviour might be compared in disassociated juvenile human males and dogs in rescue. One aspect of shared bio-psychological chemistry may be linked to associated metabolisms that result from increased levels of adrenaline and stress hormones in aggressive human males. The influence of hormones in aggression, including serotonin, has attracted research in relation to dog behaviour, Reisner et al (1996). They suggest that reduced serotonergic function is associated with aggressive behaviour and impaired impulse control in dogs. However, the role of hormones, operating alongside and outside of the nervous system, and the effect of any potential imbalance influencing aggressive dog behaviour is still not fully understood.
It is accepted by professional dog behaviourists and now many veterinarians, that castration and ovariohysterectomy, which reduces hormonal levels of androgens and oestrogen, has little, if any, effect on aggression in dogs. Takeuchi et al (2001) commented on published research and concluded that androgen may not affect dogs that display ‘stranger aggression’ (fear-associated).
Neutering does not appear to negate the effect of adrenaline (fight or flight) response in dogs. However, many veterinarians in the UK routinely advise neutering when a client requests advice on how to correctly deal with an aggressive dog in their care. Clinical experience strongly indicates that neutering an aggressive dog does not counter aggressive behaviour but on the contrary, intrusive veterinary surgery may even lead to an increase in fear-based behaviour including aggression. This is another area where a widely introduced survey and research might offer data to help our overall understanding of dog aggression.
Any reduction in testosterone or oestrogen may have some effect on juvenile entire dogs and bitches that are displaying ‘status or ‘dominance’ and aggression’ (personal observations). Chemical castration in male dogs can reduce sexual behaviour which, in turn, may counter or reduce incidents where a potential escape and subsequent uncontrolled free-roaming might lead to intrusive interaction with bitches or even aggressive episodes with other dogs.
In Bradshaw et al (2009) there is a sentence in a section, ‘Interactions between dogs and owners’, that reads: ‘Hence, where a dog is anxious about the approach of an owner in a particular context (perhaps because an owner has previously forced the dog into an alpha roll) it may show appeasement’.
It is unlikely that any professional dog behaviourists in the UK would advocate such a method and therefore it is assumed that this reference alludes to dog training tactics based in another country or advocated by trainers who hold the view that to control a dog is to dominate it. A recent example of such methods used outside of the UK are detailed in Herron et al (2009). This research may have had some influence on the ‘alpha roll’ comment as the term is specifically referred to in this research.
UK behaviourists consistently advise against attempting any form of physical aggression in order to gain control over an aggressive dog. It is also generally advised that an aggressive or nervous response directed towards their dogs could serve to reinforce any associated experiences which would escalate aggressive behaviour.
Interspecific aggression and dog-human aggression – RHP
Bradshaw et al (2009) put forward an argument that the term or trait dominance is misused when describing aggressive dogs. They state that the concept of dominance does not offer a useful contribution to explain dog-dog aggression and, because of the added complication of inter-species communication, is less likely to explain dog-human aggression
Any review of our understanding of dog aggression should consider how dog-human aggression is triggered (Appendix 3-6) and how escalation or de-escalation might be influenced in relation to how dogs perceive humans. How a dog is likely to form a fundamental risk assessment of humans before displaying aggression might be simplified if it is logically considered. Dogs do not have the brain capacity or complex processes to switch perceptions and can only ‘think like dogs’. Therefore, it can be argued that humans are most likely assessed by a dog, using its enhanced senses, in simplified social terms. It is highly likely that a dog obtains olfactory information, uses vocal-tone and visual-associations (including human facial expressions) to establish if a family, friend or stranger is an individual in its social group (human-dog) or an outsider. Ongoing assessment would involve deciding if a person is a potential competitor for resources or even a ‘threat’ or a ‘non-threat’ to itself or its social group. If the dog establishes that the person is a ‘threat’ then what follows is the fight or flight response. The outcome then is retreat to safety or display an aggressive fear-response (alert barking and growling) or predatory aggression (attack nipping and biting) in some circumstances.
Dogs, with superior scent ability to humans, are likely obtain instant hormonal information such as human-gender from testosterone and oestrogen levels. In this respect, any prior association, including learned, the potential for abuse or care from people, would be a further influence for an aggressive episode. The potential escalation or de-escalation of aggression displayed by a dog is most likely to hinge on how successful previous challenges have been and whether a fearful response is given to any challenge by the person. If aggression is being shown towards an owner or immediate family member or familiar person then this behaviour is either fear-based or what is widely known as dog dominance.
Owner and family members keeping an aggressive companion dog usually react toward them with apprehension or fear responses. Instinctive human body language reactions (associated with primary emotions), including withdrawal or hesitation, together with pheromones signalling, will allow a dog to assess whether an aggressive approach is to be successful. Dogs have a superior smelling ability to humans and are highly likely to be capable of scenting interspecies information related to human emotional and metabolic changes. This would be within the known capabilities of dogs that are equally able to scent pre-seizure states, cancerous cells and abnormal heart rhythms in people. In this respect, those who are afraid of dogs are most likely to attract their attention. This is likely to occur as a result of physical and chemical signalling which is expressed when apprehension or fear is being shown.
Owners with aggressive companion dogs may unwittingly reinforce unwanted behaviour. There is a dog ‘rough and tumble’ play mode that includes strength-testing behaviour seen in feral, and domesticated pups prior to individuals reaching sexual maturity. Competitive iner-play behaviour most likely offers strength-information of other juveniles that are future potential rivals in the period leading up to when challenges might be launched for social positioning in the adult stage.
The RHP (RV) model, when applied to juvenile dogs, could include play-fighting, tests of holding on and pulling strength when disputing ownership of fur or bones in nature. Competing behaviour, termed ‘King of the castle positioning’ in my own assessments of the behaviour, can frequently be observed around challenges for a raised area. This common behaviour can in other domesticated mammals including herd animals such as bovines especially kids, lambs and calves when rutting style head-butting and pushing between individuals occurs. Eventually, any juvenile that has tested out rivals and will have a record of the physical strength of litter siblings or herd members.
This competitive-interaction is interrupted when puppies are separated after being sold. However, a natural physical development may have an outlet and be used against owners of puppies who actively take on the role of competitor. In these situation the owner might encourage repeated tug-toy type games and inadvertently allow the dog to win. If any owner consider possessive-behaviour shown by their puppy over food and toys to be simply part of its development and, if it is allowed take up elevated-positions on furniture, stairs and on beds, then a ‘challenging’ is encouraged towards a success outcome. These home-related aspects are when challenging behaviour is inadvertently reinforced and because of what they actually represent, as variable resource values, dog-human aggression is most frequently triggered in these situations.
A ‘status-reduction program’ that counters or controls ‘aggressive competitive behaviour’ is successful, Takeuchi et al (2001), in that they assist an owner to form a more positive and safer relationship with their companion dog. Injuries to owners often occur if these dogs have an innate predisposition, or have been breed-selected, to display aggression.
Cameron (1997) indicated that what is referred to as ‘dominance-associated aggression’ is, ‘apparent in quite young puppies but does not become a significant concern to most pet owners until the dog is 6-24 months old’. In the 34 cases, 88% of owners reported a fair to excellent improvement in dominance-associated aggression after they had been given education in order to gain psychological leadership over their dogs.
It is known amongst professional behaviourists that interbitch-aggression in domesticated dogs often comes with warning and is often ‘flash point’ and therefore more difficult to counter. It has been suggested that this is due to female dogs evolving co-operation for offspring care and that they do nto require the same degree of injury-avoiding posturing behaviours seen in males. Wolves and feral dogs and domestic male dogs share posturing behaviours including those currently refereed to as dominance-positioning and submissive or appeasement postures. This dog body-language it thought to have evolved to reduce physical aggression and serious injury between individuals. Co-operation within a social structure for dog predators is essential in respect of a primary activity, such as hunting and foraging, because injured individuals would be less able or unable to take part.
One aspect of dog aggression that is frequently encountered by trainers and behaviour practitioners involves ‘leash-influence’ in intraspecific aggression. There are antisocial dogs that display aggressive tendencies towards other dogs and are more likely to show this behaviour when maintained on a lead as opposed to when they are off-lead. Potentially significant factors are whether the dog is entire or neutered and the influence for confused or mixed signalling (chemical and physical). These include those given out by owners who are apprehensive or fearful of their own dog’s behaviour when it is reactive as the aggressor. Another, more obvious, factor for aggression exhibited them when maintained on a lead would be the reduction or inability for dogs to exhibit olfactory inspections such as alternating anal or head region etiquette-sniffing.
Scenting and marking territory is a primary behaviour in dogs. Bradshaw and Nott (1995), within a section, ‘Social and communication behaviour of companion dogs’ briefly discuss the role of anal sac secretions in wolves and domesticated dogs and how they might be important in individual and territorial recognition.
Unpublished data, collected in dogs treated between 1999-2009, suggests there may be a significant association in dogs presenting ongoing anal gland conditions, displaced sexual-mounting behaviour and the likelihood of challenging-behaviour occurring. Displaced sexual-mounting, although mainly observed in entire dogs, is recorded regularly in bitch behaviour including my own observation notes during house visits to clients undertaken as part of a treatment program for antisocial behaviour.
An active anal gland can be manually emptied on a regular basis and this is often carried out by trained veterinary staff. However, dogs with acute anal gland discharge may require veterinary surgery for anal gland conditions that include impaction or infection. Any territorial uncertainty in domestic dogs is highly likely to influence marking-behaviour. The indication of increased anal gland activity in dogs could become a diagnostic sign of territorial-insecurity in dogs for veterinary practitioners once supporting empirical studies are made. If this association can be supported by further clinical evidence then the onset of an anal gland condition, once brought to the attention of a veterinary, could encourage diagnostic questions that would potentially help to identify associated antisocial behaviour and potentially lead to early treatment.
Some additional reinforcement for aggressive behaviour and future associations will also take place if owners choose to immediately leave the scene. In this situation, any confusion or competition between dogs involved in a preliminary altercation would go unresolved.
It is necessary to understand and clearly classify aspects of behaviour in companion dogs because they are dependent on us and we are mainly required in law to show control over them. Future research should perhaps be focused on how human influences may contribute towards aggressive behaviour in dogs even though these are more challenging to quantify.
Some further investigation would be appropriate in order to review current dominance-reduction programs which are introduced by working dog behaviourists to owners with aggressive dogs. These Programs are widely considered to be successful despite any conflicting nomenclature of scientific theory on the use of the terms dominance or dominant in dogs. Data would be useful to statistically test success rates and to standardise systems.
There is a place in domestic dog behaviour for the term dominance, despite the absence of any obvious hierarchy in a single, unpublished, study based on a group of dysfunctional rescue dogs. However, Parker’s RHP model may well be more useful to explain the aggression behaviour most associated with the term dominance in dogs. However, RHP-based aggression may provide a more accurate term to describe competitive, intraspecific and possessive-aggression in domestic dogs. This new term should not conflict with status-reduction programs including discipline-training and structured dog to owner interaction-control currently in use in to reduce aggression. Perhaps the aggressive behaviour observed in domestic dogs, that is clearly referred to by practitioners as dominance-related, could be identified more specifically as ‘aggressive competitive behaviour’ or RHP-related aggression. Hopefully, these terms when combined will be acceptable to both theoretical scientists and dog behaviour practitioners.
I wish to specially thank Geoff Parker, Emeritus Professor, School of Biological Sciences, University of Liverpool, for reviewing my understanding and analysis of his RHP model and asymmetric logic to aggression. Acknowledgements are also due to my working veterinary colleague, Michael Clarke MRCVS and Roger Tabor together with Colin Tennant, Fellows of the CFBA, for encouragement and discussions during the first draft of this review. I thank two anonymous reviewers for comments made to an early draft. I wish to acknowledge my clients together with all their various breeds and cross-breeds of dogs, who have allowed me into their homes in order to understand and treat interesting, unwanted-behaviours displayed by their companion animals.
Boitani, L., Francisci, F., Ciucci, P., Andreoli, G., 1995. Population biology and ecology of feral dogs in central Italy. In Serpell, J. (Ed), The Domestic Dog, Cambridge University Press, pp. 217-244.
Bradshaw, J.W.S., Nott, H.,1995. Social and communication behaviour of companion dogs, in Serpell, J. (Ed), The Domestic Dog, Cambridge University Press, pp.115-130.
Bradshaw, J.W.S., Blackwell, E. J., Casey, R. A., 2009. Dominance in domestic dogs – useful construct or bad habit? J. Vet. Behav, pp.135-144.
Cameron, D.B., 1997. Canine dominance-associated aggression concepts, incidents, and treatment in private behavior practice. Anim. Behav. Sci. 52.
Dmitrieva, T.N., Oades, R.D., Hauffa, B.P., Eggers, C., 2001. Dehydroepiandrosterone Sulphate and Corticotropin Levels Are High in Young Male Patients with Conduct Disorder: Comparisons for Growth Factors, Thyroid and Gonadal Hormones. Neuropsychobio 43, pp.134-140.
Gazzano, A., Mariti, C., Notari, L., Sighieri, C. and McBride, E.A., 2008)
Effects of early gentling and early environment on emotional development of puppies. Applied Animal Behaviour Science, 110, (3-4), 294-304.
Hare, B., Plyusnina, I., Iganacio, N., Wrangham, R., Trut,L., 2005. Social cognitive evolution in captive foxes is a correlated by-product of experimental domestication. Cur. Biol. 16, pp.226-230.
Herron, M.,E., Shofer,F.,S., Reisner, I.,.R., 2009. Survey of the use and outcome of confrontational and non-confrontational training methods in client-owned dogs showing undesired behaviors. Appl.Anim.Behav.Sci.117, issues 1-2, pp. 47-54.
Maynard Smith, J.,Parker, G.,A., 1976. The logic of asymmetric contests. Anim.Behav. 24, pp.159-175
Mech, L.D., Boitoni,L., 2003. Wolf Social ecology. In: Mech, L.D., and Boitoni,L., (Eds.). Wolves: Behavior, Ecology and Conservation , University of Chicago Press, Chicago, IL., pp.1-34.
Parker, G., A., 1974. Assessment strategy and the evolution of fighting behaviour. J. theor. Biol. 47, pp. 223-243.
Parker, G., A., Rubenstein., D.,L., 1981. Role assessment, reserve strategy and acquisition of information in asymmetric animal conflicts. Anim.Behav. 29, pp.221-240.
Pérez-Guisado, J., Muñoz-Serrano, A., 2009. Factors Linked to Dominance Aggression in Dogs. J. Anim. Vet. Adv. 8,2, pp.336-342.
Reisner, I.,.R., Mann, J.,J., Stanley, M., Huang, Y., Houpt, K.,A., 1996. Comparison of cerebrospinal fluid monoamine metabolite levels in dominant-aggressive and non-aggressive dogs. Brain Research.
Vol. 714, Issues 1-2, pp. 57-64.
Sands, D.D., 2008. Know your dog. Hamlyn, London. pp. 64-146.
Takeuchi, T.,Ogata, N., Houpt, K.,A., Scarlett, J.,M., 2001. Differences in background and the outcome of three behavior problems of dogs. Appl.Anim.Behav.Sci.70, 297-308.
Wells, D.L., Hepper, P.G., 2000. Prevalence of behaviour problems reported by owners of dogs purchased from an animal rescue shelter. App. Anim. Behav. Sci. 69.
Signs of dog Separation-related Disorder (SRD)
Repeated barking, whining or howling
Urination and defecation within the home
Destructive-chewing of floor-covering, digging or scratching at doors and door frames, shredding of bedding and damaging soft furnishing and furniture items
Research, where dogs with signs of owner-related SRD condition (often referred to as Separation anxiety a symptom-based diagnosis in children and some adults) were filmed during owner separation, strongly indicated the length of separation time is not a significant factor. An over-dependent dog with the condition, left for five minutes or five hours, will present one or more of the related behaviours during separation.
These findings indicate that dog SRD is not triggered by the length of time a dog is left alone in the home but by the immediate loss of visual contact with its owner as a result of over-dependency (attachment condition).
Footnote: The majority of healthy dogs not suffering the owner-attachment condition ‘home-alone’ rest and conserve energy and wait for owners to return.
General analysis of aggression in domestic dogs (Sands)
‘Territorial’ and Fear-based aggression is displayed around the home and surrounding territory when a dog reacts to a ‘perceived threat’ or noise or when strangers or other dogs are viewed as ‘threatening’. This behaviour is expressed as growling (warning) or barking and can be displayed as strangers are stroking or handling the dog.
‘Target-related aggression is commonly displayed as window-barking at post-person, people at the door, passerby or people leaving. This behaviour is commonly ‘fear-based’ and linked to ‘territorial-aggression’ and is extremely-addictive* (Table 4) in dogs. It can also be displayed if a person or another dog – in the home or on a walk – is ‘seen’ as a potential threat.
‘Predatory’ aggression is frequently displayed as ‘flash-point’ behaviour which leads to a person or dog being nipped or bitten. This behaviour can be associated with chronic pain or injury pr to an ongoing condition.
Status-related or ‘dominant’ aggression is usually seen in the form of ‘challenging or controlling-aggression’. When displayed as innate and selected-behaviour in livestock breeds it includes nipping and biting and can be shown to family members who are perceived as submissive to the dog. This form of aggression is frequently expressed as ‘possessive’ behaviour and can be strongly associated with ‘challenging behaviour’. Mostly seen as ‘growling over food’ or a retrieval toy and refusing to give up items such as food, toys or an owner’s belonging. There is some association to ‘frustration’ where owners report it occurs when the dog is not getting its own way such as over access to food, treats, toys, rooms or being denied access to people.
‘Intraspecific’ or dog-versus-dog aggression can develop from a time when a dog has been attacked by another (‘fear-based’) or when a dog is asserting its status, territorial ground and thresholds or ‘dominance’ onto others or protecting and competing over a resource (food, toy or access to owner).
The triggers for common forms of dog aggression
a) ‘Fear-aggression can be directed towards other dogs, owners and strangers. A dog, if ‘hyper-alert’ or when in a hyperactive state or made fearful, may growl bark at, lunge at, snap, nip or attempt to chase-off any target that is considered a ‘threat’.
This type of ‘antisocial behaviour’ is presented by a dog that has experienced social dysfunction or if a dog has been attacked by another or is reacting by association following human-initiated abuse or aggression. The fear of an attack promotes a ‘get in first’ strategy of behaviour which is (fight or flight) adrenalin-driven.
b) ‘Status-associated aggression and related ‘challenging behaviours’ can be displayed as possessive and territorial behaviour towards another dog. When directed at people, suggests a lack of ‘social-leadership’ in his owners. Challenging-dogs often form a strong-attachment with owners and can become protective of them. Once this occurs there is ‘uncertainty’ for the dog within the ‘perceived social-group’
Whilst most aspects of dog aggressive-behaviours are ‘instinctive’ (to aid survival in nature) some are potentially *‘addictive’ (Appendix 4) in domestic breeds. There can also be an influence in the dog’s early stages of development including faulty-learning’. Some problem-behaviours are displayed when hormones, including testosterone and adrenaline, closely linked to increased excitement, alertness and awareness, are at their highest. This is usually when young dogs, aged between 6-18 months, are ‘entire’.
Aggression in dogs is ‘rewarded’ in two ways
(developed from Robin Walker BVSC MRCVS)
a) Fear aggression:
Where a ‘threat’ is escaped from or ‘driven away’ and the dog, reacting to the effects of stress, is ‘rewarded’ by hormones associated with ‘reward’ and relief. The intensity of ‘relief’ gained by some dogs after they succeed in escaping, dealing with or chasing-off a perceived threat can become addictive. ‘Threats’ or targets can be represented other dogs, a person they do not trust, weekly refuge collectors, a post person or passing vehicles, cyclists and motorbikes. The ‘reward’ for dealing with a ‘target’ is greater than any ‘benefit’ that may have been gained from the aggression. This aspect can develop into highly addictive-behaviour if the frequency of aggression increases. People and dogs often leave the scene following the bout of aggressive behaviour or the dog is withdrawn. This suggests to the dog’s idea that it has succeeded in dealing with a ‘perceived threat’ to the territory.
b) Dominance or status-related aggression:
When displayed and successful a aggressive ‘challenge’ gains the dog an advantage over a resource, territory, mating, food, possession or advantage over or access to owner or family. This aggression occurs when dog is attempting to establish an advantage; wanting to compete and needing to be first all the time. This dog will continually attempt to establish its ‘social positioning’ amongst family members. This can be seen through play (always being on the dog’s terms such as when not giving up a thrown ball or toy or deliberately not returning it), through food and toy-play (growling and being possessive) and taking up vantage positioning such as standing up to or over individuals, resting on top of the stairs, on a sofa or chair. Another sign is a dog pushing forward to go through doorways and thresholds before people.
Dog aggression can be linked to ‘fearfulness’ and behaviours may develop after dysfunctional social experiences. Any significant changes involving house-moves and family members around a dog and illness can trigger behavioural problems. The introduction of other animals or another dog or puppy and children can trigger nervous aggression.
‘Target’-related and controlling-behaviour in dogs
This is type of behaviour is closely associated with ‘predator-prey’ (genetic or innate) behaviour. It is most frequently seen in ‘working-breeds’ where it has been selected-bred for livestock control rather than as a companion in domestication. It is most commonly seen in livestock, vermin-control and powerful guard-dog breeds. In the UK these are Border Collies, cross-breeds with a Collie influence, German Shepherds (Alsatians) and many Terrier breeds. Some dogs may display the behaviour as a direct result of under-stimulation when not tasked or working as a gun dog, livestock-control, fighting, guard dog or vermin control. The onset of the behaviour may also be associated with interaction-poverty and a poor environment during the developing period leading into sexual-maturity.
Any physical or emotional trauma experienced can trigger the condition and leads to hyper-alertness. This condition develops in dogs that are constantly displaying fear-based aggression. They are threatened by strangers, noise cues or events they cannot control.
Target-related form of behaviour is highly-addictive because when the original target or stimuli for the aggressive or hyperactive response is dealt with by the dog’s actions, the dog receives a ‘reward’. This ‘fix’ takes the form of increased levels of hormones, including dopamine and serotonin compounded by the effects of adrenaline. This combination most likely dominates ‘neural activity’ in the brain. In this state the dog probably loses the ability to control decisions related to stimuli and ‘perceived threats’.
‘Owner-attention’ been given at the time target-related aggression is displayed reinforces the behaviour. Reinforcing-attention might include common owner reactions such as ‘shouting’, ‘stroking’, ‘punishment’ and eye-contact.
Aggressive-hyperactive-behaviour in dogs can also be inadvertently encouraged by addiction, ‘fear’, ‘insecurity’, ‘frustration’, injury and pain and by nervous or passive-handling on the part of the owner.
Aetiology of antisocial behaviours in dogs
Active, true working dogs such as Rough, Belgian and Border Collies and German Shepherds, Gun-dogs including Cocker and Springer Spaniels, Dalmatians, Setters and Pointers, Labradors and Retrievers and Weimaraner, when kept in a home environment and not ‘worked’, appear predisposed to develop antisocial behaviour. Guard dog types and tenacious Terriers such as Fox, Jack Russell, West Highland, Cairn and Yorkshire are more likely to display ‘antisocial-behaviour’ and target-related hyperactivity and aggression when nervous or threatened. Physically powerful dogs line-bred to show territorial or hunting aggression, such as Rottweiler, Mastiff, Great Dane, Rhodesian Ridgeback, English and Staffordshire Bull Terriers, Inu, Akita, Husky Shar Pei and other powerful breeds are more likely to display these behaviours and require psychological owner-control.
Early socialisation, environment and significant changes
Nervous litter-mothers teach puppies to be the same. This is known as ‘faulty-learning’ and can be influenced by a poor environment or excessive-competition at the litter-stage or when aggression is shown by adult dogs or litter-siblings that goes unchecked. Long-term kennel dogs, ‘singleton’, large-litter puppies, badly-handled dogs and puppies are all known to develop problem behaviours. Rescue dogs or puppies and those that originate from inexperienced home breeders, working farm-bred or pet shops, commercial-kennels and puppy-farms and removed from the litter too soon and important aspects of socialisation are often disturbed by changes. Owners can influence some issues because they are not assertive enough and sometimes family members allow privileges. Changes in family work patterns, illness and physical disabilities and pregnancy, the presence of new babies, children or partners leaving home, are known to trigger behavioural problems.
Age, frustration and hormonal changes
Hormonal changes in the first 12-24 month period can also have a significant effect on dog behaviour.
Unresolved relationships (not socially established within the human-dog social group or modified pack)
Food (inadequate diet or not nourishing)
A lack of psychological stimulation.
By Dr. David Sands