Bulldogs World, a website devoted to the jowly breed, cites a stunning figure among its frequently asked questions: More than 90 percent of bulldog puppies are delivered by Caesarean section. That’s because the puppies have such enormous heads that they can’t fit through the mother’s birth canal - and that’s just the beginning of bulldog medical woes.
Birth defects, such as flat chests, have led to high puppy mortality. A skeletal disorder common to the breed causes high rates of hip dysplasia. Bulldogs’ wrinkly faces beget acne and eye problems. Their underbites often mean dental troubles. But the biggest issue is their smushed, ‘‘brachycephalic’’ faces, large palate and narrow nostrils - visages their wolf ancestors might not even recognize as canine. They can cause a bulldog to pant like mad while exercising, slobber like a fountain while resting, choke and gag while eating, suffer from heat stroke, and, to top it off, have unusually wicked flatulence.
The litany of health problems common to the English bulldog, as the breed is formally known, has been at the center of a controversy over breeding in Britain since 2008. That year, a damning BBC documentary on purebred dogs’ poor health and welfare, ‘‘Pedigree Dogs Exposed,’’ prompted several independent reports and caused the Kennel Club - the British counterpart to the American Kennel Club - to modestly revise its standards for several breeds, including the bulldog.
The debate has barely made a ripple here, across the pond, where Americans’ love for the baby-faced dogs has made them the fourth most popular breed registered with the AKC. But Niels Pedersen has been paying attention.
Pedersen, a veterinarian at the Center for Companion Animal Health, at the University of California at Davis, said he noticed the argument in Britain boiled down to two sides. On one were animal rights activists and veterinarians, who said bulldogs had been so inbred and selectively bred to conform to breed standards that they were doomed unless crossed with other breeds. On the other were breeders, who denied there was a problem or said it could be addressed through carefully engineered mating, which has for generations been done using dog pedigrees - family trees, essentially.
Pedersen, who has long researched canine genetics, figured the debate needed some science. So he and colleagues carried out a study on the DNA of 102 English bulldogs, most from the United States. What they found was sobering: A breed so lacking in genetic diversity that it would be nearly impossible to make it healthy without crossing it with other breeds.
‘‘The English bulldog is the most egregious example of getting carried away with oneself in actually designing a dog that’s as far from nature as you can possibly get,’’ said Pedersen, whose study was published last week in Canine Genetics and Epidemiology. Breeders have, he said, ‘‘created a dog that basically has been bred into a corner.’’
It got that way through the canine eugenics that created all of today’s breeds. As Pedersen’s study explains, English bulldogs are the descendants of dogs used in the bloody sport of bull-baiting 500 years ago. By the early 19th century, the spectacle had been banned, and a few of the dogs’ fans set about breeding them into smaller, shorter-faced and gentler animals. They became show dogs in Britain in 1860 and an AKC breed in 1886. The AKC’s breed standard, or precise description of its ideal look, instructs that an English bulldog should have a ‘‘massive, short-faced head’’ and a lower jaw ‘‘projecting considerably in front of the upper jaw and turning up.’’
Today, Pedersen said, bulldogs live an average of six years. Their health problems are expensive, so many end up at shelters, where they might be euthanized, the study noted. They can’t even fly with their peers: In 2010, the Transportation Department reported that about half of all dogs that die while being transported as cargo are ‘‘short-faced’’ breeds such as bulldogs. Many airlines now ban them.
To determine whether the breed’s future could be brightened, Pedersen examined the DNA of 87 breeding bulldogs from the United States, six from Finland, and the remainder from Canada, Austria, Hungary, Australia, Argentina and the Czech Republic.
The average English bulldog, the study found, was so inbred that it was ‘‘genetically equivalent to offspring of full sibling parents that came from a highly inbred’’ population of village mutts. Scant genetic diversity left ‘‘little wiggle room’’ to improve the situation, Pedersen said. To do that, he said, breeders would need to search the world for the rare English bulldogs that don’t suffer from breathing problems, birthing difficulties, cancer or other common afflictions.
‘‘Maybe only 1 in 20 dogs out there meet those favorable criteria, and you’d breed them with each other. Well, now you’re inbreeding again,’’ Pedersen said. ‘‘If you can produce a dog that still looks like a bulldog and can breathe normally and move normally, that’s okay. But I doubt it can be done.’’
Pedersen said he hopes the study will spur breeders to ‘‘do something.’’ He noted that some in Europe are outcrossing English bulldogs with another breed, the Olde English Bulldogge, to create a healthier animal called a continental bulldog.
But he didn’t sound optimistic. Between 2012 and 2016, English bulldog owners ordered more than 2,400 DNA tests from the genetics lab at the University of California at Davis to determine what coat colors a dog might pass on, the study said. During the same period, they ordered just 62 tests for a common genetic mutation that can cause bladder or kidney stones.
‘‘There are genetic diseases that [breeders] could test for, but they choose not to. Which means they’re more interested in the coat colors of their dogs,’’ Pedersen said. ‘‘The owners’ desire to own them, either as a status symbol or because they like them - and they are likable dogs - has exceeded their concern about the health and longevity of the dog.’’
The study has gotten a lot of press in Britain, where one maker of the BBC documentary wrote that might mean ‘‘a good day for Bulldogs.’’ Sean Wensley, president of the British Veterinary Association, said in a statement that the research ‘‘reflects the seriousness of the health problems associated with English bulldogs that our members are seeing in practice,’’ and he urged further revision in breed standards, including limits on muzzle shortness and consideration of outcrossing with other breeds.
In the United States, there has been no similar response. On one English bulldog forum, a few owners discussed the study, and some attributed health problems to ‘‘backyard breeders’’ who don’t stick to the breed standard - an argument the AKC has also made.
Pedersen’s study rejects that idea. It compared the 102 dogs’ DNA to that of six other ‘‘unhealthy’’ bulldogs treated at UC-Davis’s veterinary hospital for various ailments and found no genetic difference.
James Serpell, director of the University of Pennsylvania’s Center for the Interaction of Animals and Society, said in a recent interview that adherence to a breed standard means little anyway, because over the years, ‘‘people in each generation are interpreting that standard to mean something even more extreme.’’ The English bulldog standard, he noted, says ‘‘the distances from bottom of stop, between the eyes, to the tip of nose should be as short as possible.’’
Over time, Serpell said, ‘‘eventually you have a dog that has no distance between the tip of its nose and its forehead.’’
Pedersen, for his part, said he thinks dog breeding can be perfectly ethical and healthy for dogs. He added that his lab has tested one other breed that actually has less genetic diversity than the bulldog. He declined to say which, because the data haven’t been published yet. But he said the breed started out with a healthy pool, has avoided inbreeding and ‘‘looks like a normal dog.’’
‘‘It’s going to take a lot more care and money,’’ he said of keeping breeds healthy. ‘‘And a lot more knowledge about genetics.’’