Hercules the English Mastiff

Updated December 15, 2018
nine-month old, 150 pound Mastiff pup

Hercules the English Mastiff is a real dog, but most of the images you see of him are not. Get to know the story of the real Hercules so you can separate the facts from fiction.

The Real Hercules English Mastiff

The story of the Hercules came to light around 2001, when a giant of a purebred Mastiff dog named Hercules was awarded the distinction of being the current largest living dog. This distinction was granted by none other than the famous Guinness Book of Records. It doesn't mean that Hercules was the biggest dog ever to live, but that he was recognized as the heaviest alive at that time.

Path to Recognition

As the story goes, Hercules' owner John Flynn of Peabody, Massachusetts was talking about his massive Mastiff with a friend one day. John had mentioned that he weighed about 270 pounds himself, and that his dog outweighed him. A young acquaintance named David Delauri, just nine years old at the time, overheard this comment and became quite intrigued by the idea of big dogs in general. Naturally, he turned to a copy of the Guinness Book of World Records to find out how Hercules the English Mastiff rated among the competition.

Official Size Determination

Imagine young David's astonishment to learn that the current record holder listed was another Mastiff that weighed in at 296 pounds. Of course, the wheels in David's head began to turn, and after convincing John Flynn that Hercules might be a records contender, the dog was taken to the vet, where it was confirmed that the Hercules the Mastiff weighed a whopping 282 pounds and had a 38 inch neck circumference.

Declared World's Largest Living Dog

Although he hadn't surpassed the previous record holder in actual weight, that dog had passed away. As a result, Hercules became eligible for the title of largest living dog. The records were sent to Guinness for consideration. After confirming their authenticity and comparing them to other applicants, Hercules was declared the new largest living dog and entered into the record book.

Urban Legend

It's funny how people can take a little bit of fact and run with it. Sometime after reports of Hercules' record setting status, pictures purporting to be him began to circulate on the Internet. The most notable was an image that showed a man and a woman walking side by side, one holding the reins of an average looking horse, the other holding the leash of a giant Mastiff-type dog.

Hoax Image

Many people actually believed that this was a true image of the Hercules the Mastiff and his owner. It would have been amazing it that was true, but it wasn't. In the first place, the dog used in the digital photo was a Neapolitan Mastiff, a totally different breed. In the second place, even a Neapolitan doesn't reach the proportions of the dog in the photo, since it appears to be three-quarters of the size of the horse. When you consider the average horse weighs around 1,000 pounds, this was clearly impossible. The image was a hoax, but a fun one that fooled a good deal of people.

Debunking the Hoax

Eventually, some knowledgeable person noticed the breed discrepancy, and the hoax was debunked. You can compare the hoax image to the real Hercules and his owner at Snopes.com.

Bigger Dogs

Although Hercules has his place in history, he is not the biggest Mastiff on record; even his predecessor is not the heaviest dog ever recognized. A couple other famous Mastiffs have made their way into the Guinness Book of World records, and both were larger than Hercules.

  • Zorba: This giant weighed 343 pounds, stood 37 inches at the shoulder and was 8 feet, 3 inches long.
  • Cloe: Even more impressive, Cloe weighed 365 pounds, stood 38 inches tall at the shoulder and measured 8 feet, 5 inches in length.

Genetics Behind Dog Size

Have you ever wondered why dogs like Hercules, Zorba, and Cloe are so massive, while other dogs like Yorkshire Terriers and Chihuahuas are so small? After all, they share a common ancestor don't they? Genetic scientists wondered the same thing and set out to find out what led to the development of such wide size differences among the breeds. What they found was a variant in a gene known as "IGF-1". IGF-1 is found in all dogs and contains the code for a protein hormone known as "insulin-like growth factor 1". The variant identified in this gene is most commonly noted in small breed dogs, and absent in large ones. Geneticists believe this gene accounts for the divergence in size among the breeds as they followed the evolutionary trail.

The Real Story of Hercules

So there you have the story of Hercules. Although some breeders may identify their lines as Hercules English Mastiffs, this is not a separate breed. The Hercules nickname is simply used to gain greater notoriety for Mastiff lines that run on the larger side of the spectrum in the same way that the term "Teacup Chihuahua" is used to promote the tiniest specimens of the smallest dog breed. Just think, all the size hoopla comes down to one tiny variation in a single gene. Amazing!

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Hercules the English Mastiff