Bobby, a dog from Portugal, became famous last year when he was awarded the title of the world's oldest dog in the Guinness Book of Records, breaking the previous record that had held him for a century.
Bobby died in October 2023 - he was 31 years and 165 days old.
But now his title has been called into question, as some vets have questioned Bobby's age.
Authorities in the Guinness Book of Records launched an investigation.
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Bobby was a purebred Rafiero do Alentejo - a breed that has an average lifespan of 12 to 14 years.
His age was also confirmed in the Portuguese government's pet database, which is managed by the National Union of Veterinarians, Guinness World Records said last year.
But as word of his title spread, so did suspicion.
An investigation by Wired magazine showed that the Portuguese pet database stated that Bobby was born in 1992, but there was no registration that could confirm or deny this information.
There have also been doubts about old photographs showing different patterns on his fur, with some suggesting it was a completely different dog.
Doubts are growing among experts.
Danny Chambers, a fellow of the Royal College of Veterinary Surgeons, told the London Guardian that "none of his colleagues believe that Bobby was actually 31".
Now they have launched an official investigation from the Guinness Book of Records.
"While our investigation is ongoing, we have decided to temporarily pause applications for the title of oldest dog," a spokesman told the AFP news agency.
Bobby lived his whole life with the Costa family in the village of Conqueiros, near the west coast of Portugal.
His owner, Leonel Costa, said that "the veterinary elite tried to spread the idea to people that Bobby's life story is not true".
He believes that the reaction of some veterinarians came because he attributed Bobby's longevity to a human-like diet, not to feeding him pet food.
He says it was against the recommendations of many veterinarians.
"Everything would be different if we said he ate pet food for three decades," Costa said.
He added that all the conditions they were looking for from the Guinness Book of Records to confirm Bobby's age were met.
Until Bobby's death, the previous oldest dog to date was Bluey from Australia, who died in 1939, aged 29.
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