A black Lab mix has been at a Washington shelter for over 500 days. The volunteer who posted his story on TikTok thinks 'black-dog syndrome' could be to blame.

• Butter, a 3-year-old Lab mix, has been at a shelter for "over 500 days," a volunteer said on TikTok.
• The clip, posted by volunteer Julie Saraceno, has been viewed almost 156,000 times.

A viral TikTok video shows a 3-year-old black Labrador mix who has been at a Washington shelter for over 500 days, according to the volunteer who posted the footage. The video, which has been viewed over 155,000 times since it was posted on July 7, is tugging at the heartstrings of TikTok users.

In the clip, animal volunteer Julie Saraceno shows Butter, who was taken to the Benton-Franklin Humane Society in Kennewick in November 2021.

"POV you've been a shelter dog for over 500 days and nobody wants to take you home," she wrote on the clip.

Saraceno told Newsweek that Butter "always been a nervous guy, and the shelter life doesn't help much either."

Benton-Franklin is a no-kill shelter, which means that some animals can stick around for a long time, like Butter or another dog, Balto, who had been at the shelter for 483 days in June 2023. In another TikTok video, Saraceno said Butter's adoption fee is $55.

"I have no idea why someone hasn't adopted this precious face!" one commenter wrote on the July 7 video. "Come on guys, let's get this baby a home," another added.

Adult dogs stay in shelters for longer than puppies on average, Zazie Todd, an animal-behavior expert and author, wrote on her website. Todd said she compared two shelters in New York and found that puppies had an average stay of 23 days, while adult dogs stayed for almost double the time, at 42 days.

What is black-dog syndrome?

In one of her TikTok videos, Saraceno posits that Butter could be having a more extended stay because he's a black dog, and those tend to get adopted slower.

"Black dog syndrome or big black dog syndrome is a phenomenon in which black dogs are passed over for adoption in favor of lighter-colored animals," Saraceno wrote. "Observed by shelters and rescue groups across the world, BDS is an issue negatively affecting the adoption rates of black dogs."

"It definitely exists," Madeline Bernstein, president of the Society for the Prevention of Cruelty to Animals Los Angeles, told the Los Angeles Times in 2008, explaining that some people mistakenly see black dogs as mean.

Kim Saunders, the head of shelter outreach for Petfinder.com, told ABC News in 2009 that black dogs are euthanized more than lighter dogs. She also said that she thought that she believed black dogs don't photograph as well, rendering them almost invisible.

Saraceno agreed, telling Newsweek, "I do feel like, from what I've seen, black dogs stay in the shelter longer. I think it's some sort of unconscious bias people have walking through the shelter. The darker dogs just don't stand out as much in their kennel."

Whether it's because of his coloring, his "nervous" personality, or just bad luck, Butter is still available at Benton-Franklin.