Bobby, who was crowned the world's oldest dog, was stripped of his title after controversy over his real age.
Bobby, who lived in Portugal, was said to be 30 years and 268 days old when he was seven years old. It was named the oldest in the world by the Guinness Book of World Records (GWR) last February.
In October 2023, he died at the age of 31 years and 165 days.
But last month GWR I launched an investigation In Portuguese dogs after doubts were raised about his real age.
The investigation came despite his birth apparently being confirmed by the Portuguese government's pet database and the National Federation of Veterinarians.
Bobby was a purebred Ravero do Alentejo, a breed of livestock guarding dog with a life expectancy of 12 to 14 years.
When Bobby was crowned the largest dog in the world, he broke the record that had been held since 1939 by an Australian cattle dog that died at the age of 29 years and five months.
GWR has now said it has no conclusive evidence that Bobby lived that long.
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Microchip data drawn from the official Portuguese database was key to Puppy's evidence, but it emerged that microchips do not require proof of age for dogs born before 2008, Mark McKinley, GWR's records manager, said in a statement.
“With the additional veterinary statement submitted as proof of Bobby’s age that also cites the microchip data, we are left with no conclusive evidence that can conclusively prove Bobby’s date of birth,” he wrote.
He added: “Without any conclusive evidence now available to us, we cannot simply retain Bobby as the record holder and honestly claim that we are maintaining the high standards we set for ourselves.”
Bobby lived his whole life with Leonel Costa and his family in the rural village of Conqueros in Portugal.
Costa did not immediately respond to a request for comment.
In an emailed statement in January, its owner defended the title, saying Guinness World Records had spent an entire year verifying the record.