But when Kimball asked Guinness about re-verifying Spike, these vet estimates were no longer sufficient evidence. One way to estimate the age of an animal is by their teeth, something that Spike lacks, although Kimball says she still has a few loose teeth left over from Spike’s run-in with the pit bull in 2015. Without any teeth in Spike’s mouth to provide evidence, Kimball told Guinness that she was struggling to find a vet to verify her dog’s age.

“We greatly appreciate your efforts in supplying the newly requested evidence, but at this stage we are unable to re-award Spike’s record,” Guinness World Records wrote to Kimball. “His original record is not affected by this review, but it does mean that for now we are unable to recognize him—or any other claimant—as record-holder.”

Kimball is not pleased that Guinness is refusing to re-crown Spike as the world’s oldest dog. “I’m not upset that he got beat, that can happen. I am upset at the fact that they’re withholding his record, because this record should have nothing to do with this other dog,” she says.

It’s extremely difficult for vets to accurately estimate the age of an adult dog, says Louise Allum, head veterinary surgeon for the UK Royal Veterinary College’s shelter medicine program. Puppies are much easier to age because they lose their teeth in a predictable order: incisors first, then canines, premolars, and molars. Tracking the development of adult teeth is a reliable way to estimate the age of a dog up to about a year old.

“After that it gets more and more tricky,” Allum says. There are subtle tells that a dog is getting long in the tooth. Older dogs might have more tartar buildup, but that varies a lot with diet and dental care. Older dogs sometimes have cloudy eyes, but this can set in anywhere from the age of 5, 10, or even later. Some dogs go gray, others don’t. Some start to thin out in the face, while others stay chubby-cheeked all the way into old age.

All of this means that it’s near impossible to accurately assess a dog’s age once they get past a certain age. Even though Allum estimates the age of dogs as part of her day job, she still says that it comes down to a well-informed “best guess” when she has to put an age down in the medical records of a stray dog.

The only way to be sure of a pooch’s provenance is to have a record of them since their birth, or at least since they were a puppy. In the UK, dogs must be fitted with a microchip that contains a unique identifier before they are eight weeks old. A combination of microchip records and photos that show a dog aging over the years would be the most reliable indicator of a dog’s true age, Allum says, although she notes that even those records could be falsified.

Guinness World Records’ head of publishing and brand communication, Amber-Georgina Maskell, says that the company decided to review its age-verification process after receiving “some correspondence from vets” in the wake of the news of Bobi’s death. Maskell says that the company is reviewing the evidence it already has on file, seeking new evidence, and reaching out to experts and people linked to Bobi’s record-breaking claim. As Bobi was also the oldest recorded dog ever (the previous record holder, Bluey, died in 1939), that record title has also been paused. Guinness also has records for the oldest cats, llamas, and mice, but Maskell said that those categories are not currently paused.