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The Behavioral Genetics of Dogs

 
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Δημοσιεύθηκε: Παρ Νοέ 17, 2017 6:39 pm    Θέμα δημοσίευσης: Ads

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sangel



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ΔημοσίευσηΔημοσιεύθηκε: Πεμ Αύγ 04, 2011 2:04 pm    Θέμα δημοσίευσης: Απάντηση με παράθεση αυτού του μηνύματος

κ στην αγγλιστη....

The Behavioral Genetics of Dogs
That much of dog behavior has genetic underpinnings is patently obvious. Differences in temperament and ability among breeds are well known. These diffferences are generally associated with the purposes for which the breed was created. This brief summary, which is typical of how dog breeds are classified, suggests some of the traits that have been subject to selection.
1. Sheepdogs (shepherds, collies, and the like) are selected for their keen ability to focus on sheep or cattle, their ability to manipulate the behavior of these animals, and their ability to learn and follow their handler's commands. Some think that much of the herding behavior is derived from predatory behavior, but the actually killing behavior has been suppressed.
2. Terriers are energetic hunters, very attracted to small animals.
3. Scent hounds (beagles, bassets, fox and coonhounds) are able to behavioral exploit their keen sense of smell in tracking prey.
4. Retrievers (labrador, golden), known also as gun dogs, are selected for retrieving ability. A specific behavior that has been selected is a "soft mouth" the ability to handle prey without damaging the item or attempting to consume it.
5. Companions and Toys (poodles, pekinese, chihuahua) display behavioral traits that make them attractive household pets.
6. Sighthounds (afghans, borzois, greyhounds) use their vision to track prey. Generally also selected for high running speed, endurance.
In general, dog breeds that are recognized by groups like the American Kennel Club (AKC) "breed true". This means that pairing any male and any female in the breed will result in pups with the breed-specific characteristics. If you think about this, you'll recognize that the only way to accomplish "breeding true" is through reduction of genetic variation. Any one breed of dogs will have less genetic variation within the breed than you find if you look across all dogs. At some point, breeding of this sort will eliminate most or all of the additive genetic variation in the breed, at least for some traits. At the point at which the additive genetic variation has been exhausted, no further "improvement" of the breed is possible even through carefully designed pairings.
Thinking about how heritability is calculated, it follows that within any dog breed you would expect to find low heritabilities, particularly for the traits which are thought to characterize the breed. Does this mean that the traits do not have a genetic underpinning? No--not at all. It simply means that further attempts to select for the trait will be futile. Following this line of reasoning, you would expect to observe higher heritabilities for traits (including, of course, behavioral traits) if you include a variety of dog breeds in a study, and lower heritabilities if you focus on only one dog breed.
Most measures of heritabiilties of dog behavioral traits are from studies of single breeds. Ruefenacht et al (2002), for example, found heritabilities of 0.24, or less, for personality traits of German Shepherds, and present a large table summarizing heritabilities for behavioral traits in dogs. Nearly all of the studies were performed within breeds (the alternative would be to do controlled matings between breeds).
Generally heritabilities for behavioral traits range from 0 to 0.25. A wide range of behaviors have been measured, such as "willingness", fighting the leash, hare tracking, and "obedience".
These studies relate to two other interesting areas of dog behavior:
• Do dogs have personality?
What is the basis of aggression (particularly biting) in dogs?

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sangel



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ΔημοσίευσηΔημοσιεύθηκε: Πεμ Αύγ 04, 2011 2:09 pm    Θέμα δημοσίευσης: Απάντηση με παράθεση αυτού του μηνύματος

αγγλιστη νο2

What is the Basis for Aggression in Dogs?

Domestic dogs are carnivores; their close ancestors were efficient predators. The domestic dog's ancestors also used dominance and aggression to structure their societies. To be acceptable companions and work animals for humans, these instincts--predation, dominance and aggression--need to be very much reduced. In all likelihood, this process started as natural selection on dogs. Dogs that became camp-followers were able to feed on scraps, waste and discards but were probably only tolerated if they weren't a threat to their human associates. Most scientists think the evidence supports the idea that domestic dogs are derived from wolves, but, alternatively, it may be that domestic dogs are simply the evolutionary extension of a canid species that exists now only as the domestic dog (Koler-Matznick 2002). In any case, dogs and wolves can hybridize, indicating considerable genetic similarity between the two species. Wolves are not safe social companions; the amelioration of dominance and aggression in dogs, combined with the ability to the dog to integrate into a human social group using shared communication strategies (Hare et al. 2002) makes the domestic dog an appropriate household member.

As with other aspects of personality in dogs, dominance and aggression has fairly substantial heritability, indicating that selective breeding can enhance or reduce this behavior. It is unclear from studies on dogs whether predatory behavior is related to social dominance, but it, too, can be modified by selective breeding. Tests for aggression in dogs (Netto and Planta 1997; van den Berg et al.2003) allow dog breeders to rate dogs in their likelihood of expressing dominance, and when dogs with low dominance and agrression scores are bred, suitable companion animals result.

Certain breeds have been selected for enhanced dominance and aggression. Pit bulls and Rottweilers currently receive the most public attention in this regard, and pit bulls have been banned in many locations because they are perceived as being dangerous. While advocates of these breeds claim that maltreatment is a more likely underlying cause of the kind of aggression leading to biting incidents (some of which involve human fatalities), in fact we know that personality is fairly unresponsive to environment. Aggressive and dominant personalities likely only remain in check because dogs' owners have established themselves in a position of dominance over the animal, and other people are at risk, particularly when the owner is absent. Groups of dogs running loose can be particularly dangerous; human deaths often result from attacks by two to four dogs of a breed like Pit Bulls or Rottweilers which have been selected for dominance and aggression. A recent incident (November 2005), in which three pit bulls in Aurora, Colorado, mauled a 10-year old boy, illustrates this danger. The boy lost an arm and suffered disfiguring facial injuries (Meyer 2005). Not only is the attack of multiple dogs more difficult to fend off than an attack of a single dog, but there seems to be a catalytic effect among the dogs, fueling the attack.

Two analyses of human dog bite fatalities are available. A CDC report analyzed 199 deaths occuring between 1979 and 1996; the vast majority were attributed to Pit Bulls, Rottweilers, German Shepherds and wolf-dog hybrids (Anon, 1997). Sacks et al. (2000) documented 238 deaths between 1979 and 1998, and came to essentially the same conclusion. Breed-based analyses of bites, rather than fatalities, likely would yield a different picture. Small children are at greatest risk; they are most likely to be targeted by dogs who have been allowed to roam loose, and are also most likely to unknowingly wander into areas guarded or occupied by dangerous dogs. Children may be perceived by the dogs as prey, or as easy targets of dominance. Adult humans in rural areas have also been victims of attacks by groups of loose dogs. As Sacks et al. (2000) point out, it is difficult to correct these data for the relative abundances of animals of each breed, but the predominance of certain breeds in causing human fatalities is clear signal for caution with these breeds.

Although these few breeds are most likely to be involved in fatal bites, all dogs are capable of biting. Again, children are the most likely victims, as they are less likely to recognize an animal's boundaries (such as approaching an animal when it is sleeping, interfering with feeding, grabbing and pulling the dog in a way that causes pain to the animal). Clearly children and dogs must be well-supervised when together, particularly if the child is unfamiliar with dogs or the dog is unfamiliar with children. Understanding the role of dominance and aggression in dog social systems helps owners to develop strategies for integrating a new pet into their household which maintain the safety of the humans and happiness of the dog.

Puppies can be tested for aggression and dominance; they can be tested as well for other personality traits. Prospective dog owners are well-advised to do this, given the strong effect of genetics (as opposed to environment) in the expression of these behaviors in dogs.

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sangel



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ΔημοσίευσηΔημοσιεύθηκε: Πεμ Αύγ 04, 2011 2:11 pm    Θέμα δημοσίευσης: Απάντηση με παράθεση αυτού του μηνύματος

αγγλιστη νο 3
What is personality....
What is personality? And, can animals have personality? Personality is a set of attributes--such as sociability, aggressiveness, and willingness to please--that come together to form the social behavior of a species. What makes personality interesting is the variation of its expression among animals within a species, population, or social group. Scientists working on social behavior of birds or mammals are often struck by differences in personality among their study animals. This is particularly true of primates, canids, parrots and their relatives, crows and their relatives, and dolphins, but such variation can be found in a broad, and sometimes surprising, range of animals.

If personality varies among animals within a species, what function might this variation have? Variation may be the expression of different strategies, as predicted by game theory. Within this hypothesis, there are two possiblities. First, it may well be that success as a dominant animal calls for a different personality than does success as a subordinate, and expression of personality depends on status within the social group. In this type of system, an animal's personality may vary, depending on the circumstances. Second, personality may be fixed, genetically, for a given animal, but it may vary among individuals because strategies differ in their success, depending on environmental factors. If personality varies among animals, but is genetically fixed for an individual, then the study of personality lies within the realm of behavioral genetics.

Among non-human animals, personality is best known in chimpanzees and domestic dogs. In chimpanzees, personality is generally thought to be described by these variables (Weiss et al. 2000):

Dominance
Extraversion
Dependability
Emotional Stability
Agreeableness
Openness

The last five of these dimensions are thought to describe human personality (Bouchard 1994); their presence in both chimps and humans can be thought of as representing the shared evolutionary history of chimpanzees and humans. In both humans and chimpanzees, these personality traits have relatively high heritabilities and show virtually no effect of rearing environment. Human twins who are separated at birth and reared in very different environments show startling similarities in personality. In their study of chimpanzees, Weiss et al (2000) found a particularly strong heritability on social dominance, and weak heritabilities for the other dimensions of chimp personality. As in human studies of personality, Weiss et al. (2000) found little effect of environment (in this case, different zoos) on personality.

In dogs, Svartberg and Forkman (2002) identified the main variables describing personality:

Playfulness
Curiousity/fearlesness
Desire to chase
Sociability
Aggressiveness

They suggest that the first four factors are all influenced by a single "broad" personality dimension, with aggressiveness working separately. This is, interestingly, quite parallel to the role of dominance in chimpanzee personality. Wilsson and Sundgren (1997)show that dog personalities have substantial heritable components, although their study isn't strictly comparable to Svartberg and Forkman's (2002) study, as they use different descriptors of personality.

In sum, personality in animals is real, measuable, and seems to be strongly influenced by genes. Variability in personality is, in a sense, genetic variability. This suggests that different personalities can be successful and persist in evolutionary time; if only one personality type were succcessful, natural selection would eliminate this variation.

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