Dog behavior

Dogs roughhousing.

Dog behavior is the range of actions and mannerisms made by the domestic dog, Canis lupus familiaris, in conjunction with themselves or their environment, which includes other organisms as well as the inanimate physical environment. It is the response of dogs to various stimuli or inputs, whether internal or external, conscious or subconscious, overt or covert, and voluntary or involuntary.

Evolution/Domestication/Co-evolution with humans

The origin of the domestic dog (Canis lupus familiaris or Canis familiaris) is not clear. Nuclear DNA evidence points to a single domestication 11,000-16,000 years ago that predates the rise of agriculture and implies that the earliest dogs arose along with hunter-gatherers and not agriculturists.[1] Mitochondrial DNA evidence points to a domestication 18,800-32,100 years ago and that all modern dogs are most closely related to ancient wolf fossils that have been found in Europe,[2][3] compared to earlier hypotheses which proposed origins in Eurasia as well as Eastern Asia.[4][5][6] The 2 recent genetic analyses indicate that the dog is not a descendant of the extant (i.e. living) gray wolf but forms a sister clade, that the ancestor is an extinct wolf-like canid and the dog's genetic closeness to modern wolves is due to admixture.[1][7]

How dogs became domesticated is not clear, however the two main hypothesis are self-domestication or human domestication.

There exists evidence of human-canine coevolution.

Cognition

Further information: Animal cognition

Cognition describes the mental capacities of animals. Dogs have frequently been used in studies on cognition, for example, in the learning processes of classical and operant conditioning. As with many animals, the cognitive capacities of dogs are affected by both genetic and environmental factors[8] as expressed in the "nature versus nurture" debate. The great majority of modern research on dog cognition has focused on pet dogs living in human homes in developed countries. This is only a small minority of the domestic dog population and dogs from other populations may show quantifiably different cognitive behavior towards humans.[9] Furthermore, there is a possibility that breed differences can confound studies on cognitive capacity.[10]

Dogs have a general behavioral trait of strongly preferring novelty ("neophillia") compared to familiarity.[11]

As the oldest domesticated animal species, the cognitive capacities of dogs inevitably have been shaped by millennia of contact with humans.[12][13] As a result of this physical and social evolution, dogs have acquired an ability to understand and communicate with humans. Research in canine cognition is revealing the range and variability of skills such as following pointing and gaze cues,[14][15][16] fast mapping of novel words,[17] cognitive bias[18] and the possibility that dogs have other emotions.[19]

Effects of dominance

In a problem-solving experiment, dominant dogs generally performed better than subordinates, but only when they observed a human demonstrator’s actions. This indicates that social rank affects performance in social learning situations. In social groups with a clear hierarchy, dominant individuals are the more influential demonstrators and the knowledge transfer will, therefore, be unidirectional. If dog-human groups are regarded as hierarchical social units, humans are usually considered as the leaders, meaning the human will be the most influential demonstrator for the dominant dog. Subordinate dogs will learn better from the dominant dog that is adjacent in the hierarchy.[20]

Fast mapping

In humans, "fast mapping" is the ability to form quick and rough hypotheses about the meaning of a new word after only a single exposure. A study with a border collie, Rico, showed he was able to fast map. Rico initially knew the labels of over 200 different items. He inferred the names of novel items by exclusion learning and correctly retrieved those novel items immediately and also 4 weeks after the initial exposure. This retrieval rate is comparable to the performance of 3-year-old humans.[17]

Object permanence

The concept of "object permanence" relates to the ability of an animal to understand that objects continue to exist even when they have moved outside of their field of perception. Developmental psychologist Jean Piaget described the development of object permanence in human infants as having [Object permanence#Stages|six stages]]. This stepwise approach is sometimes used in studies of the cognitive abilities of non-human animals. There is ample evidence that dogs reach the advanced stage of 5 in which they are successful at “successive visible displacement” in which the experimenter will move the object behind multiple screens before leaving it behind the last visited location; Stage 5 object permanence is fully developed at 8-weeks-old. There is conflicting evidence whether dogs reach Stage 6 of Piaget’s object permanence development model.[21]

Senses

Further information: Dog § senses

Vision

Frequency sensitivity compared with humans.

Like most mammals, dogs have only two types of cone photoreceptor, making them dichromats.[22][23][24][25] These cone cells are maximally sensitive between 429 nm and 555 nm. Behavioural studies have shown that the dog's visual world consists of yellows, blues and grays,[25] but they have difficulty differentiating red and green making their color vision equivalent to red–green color blindness in humans (deuteranopia). When a human perceives an object as "red", this object appears as "yellow" to the dog and the human perception of "green" appears as "white", a shade of gray. This white region (the neutral point) occurs around 480 nm, the part of the spectrum which appears blue-green to humans. For dogs, wavelengths longer than the neutral point cannot be distinguished from each other and all appear as yellow.[25]

The dog's visual system has evolved to aid proficient hunting.[22] While a dog's visual acuity is poor (that of a poodle's has been estimated to translate to a Snellen rating of 20/75[22]), their visual discrimination for moving objects is very high; dogs have been shown to be able to discriminate between humans (e.g., identifying their human guardian) at a range of between 800 and 900 metres (2,600 and 3,000 ft), however this range decreases to 500–600 metres (1,600–2,000 ft) if the object is stationary.[22]

Olfaction

While the human brain is dominated by a large visual cortex, the dog brain is dominated by an olfactory cortex. The olfactory bulb in dogs is roughly forty times bigger than the olfactory bulb in humans, relative to total brain size, with 125 to 220 million smell-sensitive receptors. The bloodhound exceeds this standard with nearly 300 million receptors.[8]

Hearing

Anatomy of the ear.

The frequency range of dog hearing is approximately 40 Hz to 60,000 Hz,[26] which means that dogs can detect sounds far beyond the upper limit of the human auditory spectrum.[24][26][27] In addition, dogs have ear mobility, which allows them to rapidly pinpoint the exact location of a sound.[28] Eighteen or more muscles can tilt, rotate, raise, or lower a dog's ear. The ears are often used in communication of, for example, the dog's mood. A dog can identify a sound's location much faster than a human can, as well as hear sounds at four times the distance.[28]

Social behavior

Further information: Dog communication

Play

Dog-dog

Playtime

Play between dogs usually involves several behaviours that are often seen in aggressive encounters, for example, nipping, biting, growling and biting. It is therefore important for the dogs to place these behaviours in the context of play, rather than aggression. Dogs signal their intent to play with a range of behaviours including a "play-bow", "face-paw" "open-mouthed play face" and postures inviting the other dog to chase the initiator. Similar signals are given throughout the play bout to maintain the context of the potentially aggressive activities.[29]

From a young age, dogs engage in play with one another. Dog play is made up primarily of mock fights. It is believed that this behavior, which is most common in puppies, is training for important behaviors later in life. Play between puppies is not necessarily a 50:50 symmetry of dominant and submissive roles between the individuals; dogs who engage in greater rates of dominant behaviours (e.g. chasing, forcing partners down) at later ages also initiate play at higher rates. This could imply that winning during play becomes more important as puppies mature.[30]

Dog-human

The motivation for a dog to play with another dog is distinct from that of a dog playing with a human. Dogs walked together with opportunities to play with one another, play with their owners with the same frequency as dogs being walked alone. Dogs in households with two or more dogs play more often with their owners than dogs in households with a single dog, indicating the motivation to play with other dogs does not substitute for the motivation to play with humans.[31]

It is a common misconception that winning and losing games such as "tug-of-war" and "rough-and-tumble" can can influence a dog's dominance relationship with humans. Rather, the way in which dogs play indicates their temperament and relationship with their owner. Dogs that play rough-and-tumble are more amenable and show lower separation anxiety than dogs which play other types of games, and dogs playing tug-of-war and "fetch" are more confident. Dogs which start the majority of games are less amenable and more likely to be aggressive.[32]

Playing with humans can affect the cortisol levels of dogs. In one study, the cortisol responses of police dogs and border guard dogs was assessed after playing with their handlers. The cortisol concentrations of the police dogs increased, whereas the border guard dogs' hormone levels decreased. The researchers noted that during the play sessions, police officers were disciplining their dogs, whereas the border guards were truly playing with them, i.e this included bonding and affectionate behaviours. They commented that several studies have shown that behaviours associated with control, authority or aggression increase cortisol, whereas play and affiliative behaviour decrease cortisol levels.[33]

Empathy

In 2012, a study found that dogs oriented toward their owner or a stranger more often when the person was pretending to cry than when they were talking or humming. When the stranger pre-tended to cry, rather than approaching their usual source of comfort, their owner, dogs sniffed, nuzzled and licked the stranger instead. The dogs’ pattern of response was behaviorally consistent with an expression of empathic concern.[34]

Personalities

Several personality traits in dogs are recognised. These include "Playfulness", "Curiosity/Fearlessness, "Chase-proneness", "Sociability and Aggressiveness" and "Shyness–Boldness".[35][36]

Leadership, dominance and social groups

Follow the leader

Dominance is a descriptive term for the relationships between pairs of individuals. Among ethologists, dominance is normally defined as ‘‘an attribute of the pattern of repeated, agonistic interactions between two individuals, characterized by a consistent outcome in favor of the same dyad member and a default yielding response of its opponent rather than escalation. The status of the consistent winner is dominant and that of the loser subordinate.’’[37] There is no reason to assume that a high-ranking individual in one group would also become high ranking if moved to another. Nor is there any good evidence that ‘‘dominance’’ is a lifelong character trait. Competitive behavior was characterized by confident (e.g. growl, inhibited bite, stand over, mount, stare at, chase, bark at) and submissive (e.g. crouch, avoid, displacement lick/yawn, run away) patterns exchanged.[38]

One test to ascertain which in a group was the dominant dog used the following criteria: When a stranger comes to the house, which dog starts to bark first or if they start to bark together, which dog barks more or longer? Which dog licks more often the other dog’s mouth? If the dogs get food at the same time and at the same spot, which dog starts to eat first or eats the other dog’s food? If the dogs start to fight, which dog wins usually?[39]

Domestic dogs appear to pay little attention to relative size, despite the large weight differences between the largest and smallest individuals; for example, size was not a predictor of the outcome of encounters between dogs meeting while being exercised by their owners nor was size correlated with neutered male dogs.[40] Therefore, many dogs do not appear to pay much attention to the actual fighting ability of their opponent, presumably allowing differences in motivation (how much the dog values the resource) and perceived motivation (what the behavior of the other dog signifies about the likelihood that it will escalate) to play a much greater role.[38]

Two dogs that are contesting possession of a highly valued resource for the first time, if one is in a state of emotional arousal, or if one is in pain, or if reactivity is influenced by recent endocrine changes or motivational states such as hunger, then the outcome of the interaction may be different than if none of these factors were present. Equally, the threshold at which aggression is shown may be influenced by a range of medical factors, or, in some cases, precipitated entirely by pathological disorders. Hence, the contextual and physiological factors present when 2 dogs first encounter each other may profoundly influence the long-term nature of the relationship between those dogs. The complexity of the factors involved in this type of learning means that dogs may develop different ‘‘expectations’’ about the likely response of another individual for each resource in a range of different situations. Puppies learn early not to challenge an older dog and this respect stays with them into adulthood. When adult animals meet for the first time, they have no expectations of the behavior of the other: they will both, therefore, be initially anxious and vigilant in this encounter (characterized by the tense body posture and sudden movements typically seen when 2 dogs first meet), until they start to be able to predict the responses of the other individual. The outcome of these early adult–adult interactions will be influenced by the specific factors present at the time of the initial encounters. As well as contextual and physiological factors, the previous experiences of each member of the dyad of other dogs will also influence their behavior.[38]

Feral dogs

In 2004, a study reviewed 5 other studies of feral dogs published between 1975 and 1995 and concluded that their pack structure is very loose and rarely involves any cooperative behavior, either in raising young or in obtaining food.[41] Feral dogs are primarily scavengers, with studies showing that unlike their wild cousins, they are poor ungulate hunters, having little impact on wildlife populations where they are sympatric. However, feral dogs have been reported to be effective hunters of reptiles in the Galápagos Islands.[42]:267

Reproduction behavior

Further information: Canine reproduction

Estrous cycle and mating

Although puppies do not have the urge to procreate, males sometimes engage in sexual play in the form of mounting, as early as 5 weeks-of-age.

Dogs reach sexual maturity and can reproduce during their first year, in contrast to wolves at two years-of-age. Bitches have their first estrus ("heat") at 6 to 12 months-of-age; smaller dogs tend to come into heat earlier whereas larger dogs take longer to mature.

Dog bitches have an estrous cycle that is nonseasonal and monestrus, i.e. there is only one estrus per estrous cycle. The interval between one estrus and another is, on average, seven months, however, this may range between 4 to 12 months. This interestrous period is not influenced by the photoperiod or pregnancy. The wolf, coyote, Australian dingo and African basenji may have only one, seasonal, estrus each year.[43]

For several days before estrus, a phase called proestrus, the bitch may show greater interest in male dogs and "flirt" with them (proceptive behavior). There is progressive vulval swelling and some bleeding. If males try to mount a bitch during proestrus, she may avoid mating by sitting down or turning round and growling or snapping.

Estrous behavior in the bitch is usually indicated by her standing still with the tail held up, or to the side of the perineum, when the male sniffs the vulva and attempts to mount. This tail position is sometimes called “flagging”. The bitch may also turn, presenting the vulva to the male, The average duration od estrus is 9 days with spontaneous ovulation usually about 3 days after the onset of estrus.[43]

The male dog mounts the female and because he has a bone in his penis (the Os penis), he is able to acieve intromission with a non-erect penis. The penis enlarges inside the vagina, thereby preventing its withdrawal; this is sometimes known as the “tie” or “copulatory lock”. The male dog rapidly thrust into the female for 1-2 minutes then dismounts with the erect penis still inside the vagina, and turns to stand rear-end to rear-end with the bitch for up to 30 to 40 minutes; the penis is twisted 180 degrees in a lateral plane. During this time, prostatic fluid is ejaculated.[43]

The bitch can bear another litter within 8 months of the previous one. Dogs are polygamous in contrast to wolves that are generally monogamous. Therefore dogs have no pair bonding and the protection of a single mate, but rather have multiple mates in a year. The consequence is that wolves put a lot of energy into producing a few pups in contrast to dogs that maximize the production of pups. This higher pup production rate enables dogs to maintain or even increase their population with a lower pup survival rate than wolves, and allows dogs a greater capacity than wolves to grow their population after a population crash or when entering a new habitat. It is proposed that these differences are an alternative breeding strategy, one adapted to a life of scavenging instead of hunting.[44]

Parenting and early life

All of the wild members of the genus Canis display complex coordinated parental behaviors. Wolf pups are cared primarily by their mother for the first 3 months of their life when she remains in the den with them while they rely on her milk for sustenance and her presence for protection. The father brings her food. Once they leave the den and can chew, the parents and pups from previous years regurgitate food for them. Wolf pups become independent by 5 to 8 months, although they often stay with their parents for years. In contrast, dog pups are cared for by the mother and rely on her for milk and protection but she gets no help from the father nor other dogs. Once pups are weaned around 10 weeks they are independent and receive no further maternal care.[44]

Behavior problems

A survey of 203 dog owners in Melboourne, Australia, found that the main behaviour problems reported by owners were overexcitement (63%) and jumping up on people (56%).[45]

Separation anxiety

When dogs are separated from humans, usually the owner, they often display behaviours such as destructiveness, faecal or urinary elimination, hypersalivation or vocalisation. Dogs from single-owner homes are approximately 2.5 times more likely to have separation anxiety compared to dogs from multiple-owner homes. Futhermore, sexually intact dogs are only one third as likely to have separation anxiety as neutered dogs. The sex of dogs and whether their is another pet in the home do not have an affect on separation anxiety.[46]

Tail chasing

Tail chasing can be classified as a stereotypy. In one clinical study on the behaval problem, 18 tail-chasing terriers were given clomipramine orally at a dosage of 1 to 2 mg/kg (0.5 to 0.9 mg/lb) of body weight, every 12 hours. Three of the dogs required treatment at a slightly higher dosage range to control tail chasing, however, after 1 to 12 weeks of treatment, 9 of 12 dogs were reported to have a 75% or greater reduction in tail chasing.[47]

Behavior compared to other canids

Socialization

The critical period for socialization begins with to walk and explore the environment. Dog and wolf pups both develop the ability to see, hear and smell at 4 weeks of age. Dogs begin to explore the world around them at 4 weeks of age with these senses available to them, while wolves begin to explore at 2 weeks of age when they have the sense of smell but are functionally blind and deaf. The consequences of this is that more things are novel and frightening to wolf pups. The critical period for socialization closes with the avoidance of novelty, when the animal runs away from - rather than approaching and exploring - novel objects. For dogs this develops between 4-8 weeks of age. Wolves reach the end of the critical period after 6 weeks, after which it is not possible to socialize a wolf.[44]

Dog puppies require as little as 90 minutes of contact with humans during their critical period of socialization to form a social attachment. This will not create a highly social pet but a dog that will solicit human attention.[48] Wolves require 24 hours contact a day starting before 3 weeks of age. To create a socialized wolf the pups are removed from the den at 10 days of age, kept in constant human contact until they are 4 weeks old when they begin to bite their sleeping human companions, then spend only their waking hours in the presence of humans. This socialization process continues until age 4 months, when the pups can join other captive wolves but will require daily human contact to remain socialized. Despite this intensive socialization process, a well-socialized wolf will behave differently to a well-socialized dog and will display species-typical hunting and reproductive behaviors, only closer to humans than a wild wolf. These wolves do not generalize their socialization to all humans in the same manner as a socialized dog and they remain more fearful of novelty compared to socialized dogs.[49]

In 1982, a study to observe the differences between dogs and wolves raised in similar conditions took place. The dog puppies preferred larger amounts of sleep at the beginning of their lives, while the wolf puppies were much more active. The dog puppies also preferred the company of humans, rather than their canine foster mother, though the wolf puppies were the exact opposite, spending more time with their foster mother. The dogs also showed a greater interest in the food given to them and paid little attention to their surroundings, while the wolf puppies found their surroundings to be much more intriguing than their food or food bowl. The wolf puppies were observed taking part in antagonistic play at a younger age, while the dog puppies did not display dominant/submissive roles until they were much older. The wolf puppies were rarely seen as being aggressive to each other or towards the other canines. On the other hand, the dog puppies were much more aggressive to each other and other canines, often seen full-on attacking their foster mother or one another.[50]

Cognition

Despite claims that dogs show more human-like social cognition than wolves,[14][15][51] several recent studies have demonstrated that if wolves are properly socialized to humans and have the opportunity to interact with humans regularly, then they too can succeed on some human-guided cognitive tasks,[52][53][54][55][56] in some cases out-performing dogs at an individual level.[57] Similar to dogs, wolves can also follow more complex point types made with body parts other than the human arm and hand (e.g. elbow, knee, foot).[56] Both dogs and wolves have the cognitive capacity for prosocial behavior toward humans, however it is not guaranteed. For canids to perform well on traditional human-guided tasks (e.g. following the human point) both relevant lifetime experiences with humans - including socialization to humans during the critical period for social development - and opportunities to associate human body parts with certain outcomes (such as food being provided by human hands, a human throwing or kicking a ball, etc.) are required.[58]

After undergoing training to solve a simple manipulation task, dogs that are faced with an insoluble version of the same problem look at the human, while socialized wolves do not.[51]

Reproduction

Dogs reach sexual maturity and can reproduce during their first year in contrast to a wolf at two years. Dogs are not reliant on seasonality for reproduction i.e. at a particular time of year in contrast to a wolf at one each year. The dog female can bear another litter within 8 months of the last one. Dogs are polygamous in contrast to wolves that are generally monogamous. Therefore dogs have no pair bonding and the protection of a single mate, but rather have multiple mates in a year. The consequence is that wolves put a lot of energy into producing a few pups in contrast to dogs that maximize the production of pups. This higher pup production rate enables dogs to maintain or even increase their population with a lower pup survival rate than wolves, and allows dogs a greater capacity than wolves to grow their population after a population crash or when entering a new habitat. It is proposed that these differences are an alternative breeding strategy adapted to a life of scavenging instead of hunting.[44]

Dogs in human society

Research has shown that there are individual differences in the interactions between dogs and their human masters that have significant effects on dog behavior. In 1997, a study showed that the type of relationship between dog and master, characterized as either companionship or working relationship, significantly affected the dog's performance on a cognitive problem-solving task. They speculate that companion dogs have a more dependent relationship with their owners, and look to them to solve problems. In contrast, working dogs are more independent.[59]

Dogs in the family

Further information: Companion dog

Dogs at work

Service dogs are those that are trained to help people with disabilities. Detection dogs are trained to using their sense of smell to detect substances such as explosives, illegal drugs, wildlife scat, or blood. In science, dogs have helped humans understand about the conditioned reflex.

Attacks

A dog's teeth can inflict serious injuries

In the UK between 2005 and 2013, there were 17 fatal dog attacks. In 2007-08 there were 4,611 hospital admissions due to dog attacks, which increased to 5,221 in 2008-09. It has been estimated that more than 200,000 people a year are bitten by dogs in England, with the annual cost to the National Health Service of treating injuries about £3 million.[60] A report published in 2014 stated there were 6,743 hospital admissions specifically caused by dog bites, a 5.8% increase from the 6,372 admissions in the previous 12 months.[61]

In the US between 1979 and 1996, there were more than 300 human dog bite-related fatalities.[62] In the US in 2013, there were 31 dog-bite related deaths. Each year, more than 4.5 million people in the US are bitten by dogs and almost 1 in 5 require medical attention.[63]

See also

References

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