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The world’s largest dog is a Great Dane named Zeus, who stands 3 foot 8 inches tall and weighs 150 pounds. On his hind legs, Zeus is 7 feet 4 inches – by comparison, the NBA lists only 20 players ever to be 7 foot 3 or taller.

Zeus is three years old and eats about 12 cups of dog food per day. Giant dog breeds, which include Great Danes, tend to grow rapidly but overall they take longer to reach maturity than other types of dogs.

In prehistory, dogs may have been even larger: the largest wild dog of all time was Hayden’s bone-crushing dog. Based on fossil evidence, the wild beast was estimated to weigh up to 1374.8 pounds, and lived for 15.3 million years during the mid-late Miocene epoch in North America.

As for dogs living today, the largest breeds are:

  • Spanish Mastiff
  • English Mastiff
  • Saint Bernard
  • Pyrenean Mastiff
  • Leonberger
  • Newfoundland
  • Great Dane
  • Irish Wolfhound
  • Borzoi

Despite being able to eat things off the table and reign supreme on the couch, being big brings with it some health problems. Large dogs can have problems with their joints and with managing a healthy weight. Large breeds are also quite prone to osteosarcoma (bone cancer) and susceptible to other debilitating bone and cartilage diseases. This happens because of the amount of growth that they go through during their lives, and the long time it takes to reach maturity. In addition, the life span of big dogs is generally shorter than that of smaller dogs, often living only 6 to 10 years.

On the other hand, they typically don't need as much exercise as small and mid-size breeds, paradoxically making them good companions for city dwellers with small apartments. They also tend to have mellow, sweet personalities.

The world’s heaviest dog is a Mastiff named Hercules who tips the scales at 282 pounds. He reportedly has a 38-inch neck.

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