The Dog Days of Summer: Hybrid Dogs

Adapted from pages 180-181 of The Dog:

Data suggest that, on average, mixed breeds and crossbreeds have some health advantages over purebreds, probably because they are less inbred. As they have much higher genetic variation, they are less likely to suffer from inherited genetic diseases and more likely to live longer than purebreds.

Behavioral studies detected differences between mixed breeds and purebred dogs. Mixed-breed dogs were generally reported to be more disobedient, more nervous, more excitable, and more fearful. Excessive barking was also more frequent in their case.

They were also reported to be more aggressive toward unfamiliar people, more sensitive to touch, and had an increased risk of developing behavior problems (such as noise phobia) than purebreds. One may assume that most differences emerge because mixed-breed dogs experience less optimal early socialization and their genetic constitution also differs.

A whippet mix with a strong resemblance to the small greyhound is always ready to run. Photo credit: Grigorita Ko, Shutterstock

It is possible that a large proportion of present-day mixed breeds with unknown genetic histories originate from populations that have been under continuous selection for independent survival skills, making them more independent, assertive and more nervous/ alert. In contrast, dog breeders generally selectively breed dogs that make good human companions, focusing on favorable (calmer) behavior characteristics. Despite the different selective forces, numerous mixed-breed individuals obviously do make ideal companion dogs, as the magnitude of the differences between mixed breeds and purebreds are small.

Hybrid vigor is also known as heterosis or enhancement of outbreeding. The first generation of crossing dogs from two different breeds (or lines within a breed) produces hybrids with usually positive overall effects on health and biological functions. The explanation is that these individuals more likely inherit different gene variants (heterozygosity) that make them more resistant to environmental challenges, including pathogens.

Heterozygosity may be advantageous in other cases as well. Whippets with a single copy of a mutated gene that affects muscle composition are more muscular, and are among the fastest dogs in racing. However, whippets with two copies of the same mutation (homozygosity) develop too much muscle, which makes them rather slower.

The Dog: A Natural History
By Ádám Miklósi

As one of the oldest domesticated species, selectively bred over millennia to possess specific behaviors and physical characteristics, the dog enjoys a unique relationship with humans. More than any other animal, dogs are attuned to human behavior and emotions, and accordingly play a range of roles in society, from police and military work to sensory and emotional support. Selective breeding has led to the development of more than three hundred breeds that, despite vast differences, still belong to a single species, Canis familiaris.

The Dog is an accessible, richly illustrated, and comprehensive introduction to the fascinating natural history and scientific understanding of this beloved species. Ádám Miklósi, a leading authority on dogs, provides an appealing overview of dogs’ evolution and ecology; anatomy and biology; behavior and society; sensing, thinking, and personality; and connections to humans.

Illustrated with some 250 color photographs, The Dog begins with an introductory overview followed by an exploration of the dog’s prehistoric origins, including current research about where and when canine domestication first began. The book proceeds to examine dogs’ biology and behavior, paying particular attention to the physiological and psychological aspects of the ways dogs see, hear, and smell, and how they communicate with other dogs and with humans. The book also describes how dogs learn about their physical and social environments and the ways they form attachments to humans. The book ends with a section showcasing a select number of dog breeds to illustrate their amazing physical variety.

Beautifully designed and filled with surprising facts and insights, this book will delight anyone who loves dogs and wants to understand them better.

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