Читать книгу Animal Behavior for Shelter Veterinarians and Staff - Группа авторов - Страница 32

The result of just a few hundred years of specific breeding has made dogs as diverse in size and morphology as the Great Dane and the Maltese. Appearance‐based variations have driven the breeding of dogs with markedly different body sizes, head sizes and shape, nose lengths, weight, leg lengths, coats, tail lengths, and shape (Bateson 2010). As discussed earlier, changes in “communicative anatomy” can affect intraspecific social behavior (Horowitz and Hecht 2014). While dogs have existed as a separate species from wolves for thousands of years, for most of that time, there were not segregated, genetically isolated breeds. Ancient art and writing suggest that there were distinctive types of dogs, from mastiff‐type dogs and saluki‐shaped dogs, to small, terrier‐like lapdogs. However, these were not “purebred” dogs as the word is used today. Dogs were selected for their function: for instance, for herding, guarding, hunting, and as companions (Grier 2006). Today, by contrast, there are an estimated 400 breeds as well as “mixed breeds.” The word “breed” is now used to describe a genetically closed population of animals whose members share many physical and behavioral traits. While early dogs were the result of normal evolutionary processes and geographic segregation as well as some human selection, today’s “purebred” dogs are entirely the result of artificial selection: that is, dogs are specifically bred with other dogs of the same genetic lineage (Serpell and Duffy 2014). Initially, dogs with desirable traits and appearance were mated with dogs of similarly desirable features, creating new named breeds: German shepherd, pug, golden retriever, Akita, and so on. Some breed members resemble the imagery of ancient dogs, but there is no evidence of a continuous link between the purebred mastiffs and salukis of today and the ancient versions. Shortly after the inception of a breed line, the line is genetically closed, and future pups must be bred exclusively from other members of the breed (Wayne and Ostrander 2007).

The rise of purebred dogs began in the late nineteenth century with the advent of dog breed clubs and dog shows, also known as “the dog fancy”. In contrast with the function‐based selection of early dogs, purebred dogs have been bred largely to have a particular appearance consistent with a breed “standard”—the description of the ideal appearance and temperament of members of a breed. Extreme breed standards for specific appearance can be physically damaging: to give just one instance, dogs with large heads, such as the Boston terrier and bulldog, must be birthed surgically since they cannot fit out the birth canal of their mothers (Bateson 2010; numerous other deleterious predispositions are described in Asher et al. 2009).

Distinct behavioral tendencies seen in various breeds can reflect genetic changes that often lead to the expression (or change the intensity) of certain behaviors, given an environment that supports that behavior. For instance, the border collie, often used and bred as a herding dog, performs behaviors like showing “eye” (fixing one’s gaze at an animal), “stalking” (creeping toward the animal while maintaining eye), and chasing (Coppinger and Schneider 1995). A dog's predisposition to these actions can be molded, with training, into sheep‐herding behavior. Other examples of breed tendencies abound: the pointer's tendency to “point” with his body toward game; the retriever's ability to fetch and retrieve game in water or on land; a hound's vocalizations while tracking an animal with his nose; and coursing dogs' running pursuit of game.

In J. P. Scott and J. L. Fuller's classic longitudinal studies of five breeds of dogs (sheltie, cocker spaniel, basenji, beagle, and fox terrier), they noticed distinct differences between the breeds on scales of emotional reactivity, trainability, problem‐solving behavior, and other capacities (Scott and Fuller 1965). Subsequent studies continue to identify breed‐based heritability of complex behavioral traits (MacLean et al. 2019). For instance, golden retrievers tend to rank highly on trainability, while the beagle ranks low; huskies rank low on attention‐seeking, while dachshunds and toy poodles rank high (Serpell and Duffy 2014). At the same time, variance within breed is also observed (Mehrkam and Wynne 2014). A study of impulsiveness—the inability to inhibit behavior in the presence of particular cues—found differences between breeds but also within breed, particularly according to working, show, or pet lines (Fadel et al. 2016). While dog behavioral traits may have genetic influences, neither breed nor genetics will predict an individual dog’s behavior.

For contemporary dogs who are not employed as working dogs, their behavioral tendencies may be more problematic than functional. For instance, a border collie without sheep to herd may take to stalking and chasing bicyclists and small children who are running. Pursuit of and nipping at the motion of feet in the dog’s vicinity is typically an undesired behavior and may even be perceived as “aggressive.” A guard dog's barking at legitimate guests may be considered inappropriately “dominant” or “territorial.” Owners may wield ill‐suited measures to try to fend off this perceived threat to their authority (Herron et al. 2009). In both cases, the tendencies that humans have bred into the dogs are recharacterized as “misbehavior” in a companion‐dog context. Giving a new owner some understanding of the breed tendencies of a dog will assist the owner in working appropriately with what could otherwise be considered puzzling or disturbing dog behavior at home.