Dog - Dog Breeds & Reproduction

There are numerous dog breeds, over 800 being recognized by various kennel clubs worldwide. As all dog breeds have been derived from mixed-breed dog populations, the term "purebred" has meaning only with respect to a certain number of generations. Moreover, many dogs, especially outside the United States and Western Europe, belong to no recognized breed.

 

A few basic breed types have evolved gradually during the domesticated dog's relationship with man over the last 10,000 or more years, but most modern breeds are of relatively recent derivation. Many of these are the product of a deliberate process of artificial selection. Because of this, some breeds are highly specialized, and there is extraordinary morphological diversity across different breeds. Despite these differences, dogs are able to distinguish dogs from other kinds of animal.

 

The definition of a dog breed is a matter of some controversy. Some groups use a definition that ultimately requires extreme in-breeding to qualify. Dogs that are bred in this manner often end up with severe health problems. Other reorganizations define a breed more loosely, such that an individual may be considered of one breed as long as, say, three of its grandparents were of that breed.

 

These considerations come into play among breeders who enter their dogs in dog shows. Purebred dogs frequently suffer from serious inherited health and/or behavioral problems. This is by no means true of the majority of purebred dogs, and the same problems can occur in populations of mixed breed dogs. Even prize-winning purebred dogs are sometimes possessed of crippling genetic defects due to inbreeding.

 

In February 2004, the Canine Studies Institute in Aurora, Ohio, managed to arrange all breeds of dog into ten categories, according to Darwinian evolutionary principles.

 

The behavior and appearance of a dog of a particular breed can be predicted fairly accurately, while mixed-breed dogs show a broader range of innovative appearance and behavior.

 

A mixed-breed dog.

 

 

Mixed-breed dogs are dogs that do not belong to specific breeds, being mixtures of two or more. Mixed breeds, or dogs with no purebred ancestry, are not inherently "better" or "worse" than purebred dogs as companions, pets, working dogs, or competitors in dog sports. Sometimes mixed-breed dogs are deliberately bred, for example, the Cockapoo, a mixture of Cocker Spaniel and Miniature Poodle.

 

Such deliberate crosses may display hybrid vigor and other desirable traits, but can also lack one or more of the desired traits of their parents, such as temperament or a particular color or coat. However, without genetic testing of the parents, the crosses can sometimes end up inheriting genetic defects that occur in both parental breeds. Deliberately crossing two or more breeds is also a manner of establishing new breeds.

 

Dog Reproduction

As with most domesticated species, one of the first and strongest effects seen from selective breeding is, logically enough, selection for cooperation with the breeding process as directed by humans. In dogs, this takes the form of abolition of the pair bonding seen in wild canines, as well as the ability of female domestic dogs to come into estrus (also called in season or in heat) at any time of the year and usually twice a year; unlike undomesticated canine species where the females typically come into once season a year, usually in late winter, and bear one litter of young. Most bitches come into season for the first time between 6 and 12 months, although some larger breeds delay until as late as 2 years.

 

Like most mammals, the age that a bitch first comes into season is mostly a function of her current body weight as a proportion of her body weight when fully mature, rather than age, with the different maturation rates of the various sizes of dogs accounting for this variation in age of first season. The amount of time between cycles varies greatly among different dogs, but a given dog's cycle tends to be consistent through her life. Dogs bear their litters roughly 9 weeks after insemination.

 

Catahoula Leopard Dog nursing litter of puppies.

 

 

An average litter consists of about six puppies, especially for breeds that have not strayed too far from their wild ancestors. However, litters of many more or only one or two puppies are also common. Some breeds have a tendency to produce very large litters. Since a mother can provide milk for only a few of those puppies, humans must assist in the care and feeding when the litter exceeds eight or so.

Some breeds have been developed to emphasize certain physical traits beyond the point at which they can safely bear litters on their own. For example, the Bulldog often requires artificial insemination and almost always requires cesarean section for giving birth.

 

Puppies often have characteristics that do not last beyond early puppyhood. For example, eyes are often blue when they first open but change to other colors as the puppy matures. As another example, Kerry Blue Terrier puppies have black coats when they are born and their distinctive "blue" color appears gradually as the puppy nears maturity. The ears of erect-eared breeds such as the German Shepherd Dog are softly folded at birth but straighten as the puppy grows; in cases where they fail to straighten on their own, owners sometimes opt for surgical intervention.

 

Dog experts advise that dogs not intended for further breeding should be spayed or neutered so that they do not have undesired puppies, which are often abandoned. Abandoned dogs who go feral are particularly dangerous; they lack the skills of wild canines at survival in the wild, as well as the genetic and learned fear of humans that keeps wild canines away from humans and their possessions, so they form predatory packs that attack livestock and occasionally also prove dangerous to humans.

 

Wild dogs are shot by farmers in an effort to protect livestock. Bodies are usually tied to fences as warning to other dogs.

 

 

The overpopulation of unwanted dogs is so great that almost all dogs who end up in animal shelters are euthanized due to lack of space and resources. Spaying and neutering can also help prevent hormone-driven diseases such as breast cancer and prostate cancer, as well as undesired hormone-driven behaviors.

 

Contrary to myth, it is not required for a female dog to either experience a heat cycle or have puppies before spaying, and likewise, a male dog does not need the experience of mating before neutering; these myths are responsible for numerous unnecessary health problems and unwanted puppies. Attempts by owners to carry on some particular admirable qualities of their dogs by breeding them usually fail. Dogs of mixed breed do not "breed true"; i.e., with a mixed breed dog the offspring may not carry characteristics found in a parent, or even shared by both parents.

 

Similarly, but to a lesser extent, even with purebreed dogs sold as pets the offspring may not have the subtle best qualities of the parents; it may be necessary to go back to the high quality breeding stock and reproduce the original mating as closely as possible to reproduce the desired characteristics very closely. Of course, most owners who let their dogs reproduce will feel the offspring are superior; however, realistically speaking, the natural sentimental bias makes it just as likely that they would feel the same way about any dog they acquired, from the pound or elsewhere.