Animal welfare organizations across the region are waiving adoption fees for guinea pigs this weekend following a large surrender, shining the spotlight on a new ordinance that bans the sale of the critters at pet shops in Boston.

Recently, the Animal Rescue of League received 55 guinea pigs from a single home, with MSPCA-Angell taking in 20 of the pets. The surrender prompted the two agencies to team up with Dakin Humane, Lowell Humane, and the Animal Protection Center of Southeastern Massachusetts in hosting the fee-waived adoption event.

The event starts Friday and runs through Sunday, with the $30 adoption fee for guinea pigs being waived. In total, the groups are hoping more than 100 guinea pigs will find their new homes.

“Their owners purchased guinea pigs from pet stores where they were incorrectly sexed, resulting in many litters,” MSPCA-Angell said of the 55 surrenders on X, the former Twitter platform. “This underscores the importance of measures like Boston’s recently passed ban on guinea pig sales in pet shops.”

Mayor Michelle Wu, just before Christmas, signed the ordinance that the City Council passed in early December banning the sale of guinea pigs at pet shops across the city.

City officials enacted a “pet shop” ordinance in 2016, prohibiting the sale of dogs, cats and rabbits, except in cooperation with an animal shelter or rescue organization. It left out guinea pigs, a “significant share” of which come from large-scale, out-of-state commercial breeding facilities and brokers,” the ordinance states.

“Pet shelters across the country have seen an influx of guinea pigs being surrendered since the COVID-19 pandemic, with Animal Care Centers of New York City reporting that guinea pig surrenders have doubled since 2019,” the ordinance states.

The increase is being felt in Boston, with the city’s Animal Care and Control reporting significant increases in intakes year over year from 2020 through 2022.

Guinea pigs usually have lengthy stays at the MSPCA before being eventually adopted, said Deborah Bobek, director of operations at the MSPCA. In 2022, the average stay was 29 days compared to 18 for dogs and 13 for cats, she said during a December hearing on the ordinance.

In early December, 44 guinea pigs at MSPCA, some of whom had been waiting four months to be adopted, Bobek said. The agency hosted five fee-waived adoption events, she added.

“The events are the only thing keeping us from drowning in guinea pigs,” Bobek said. “However, despite their success in helping us place more guinea pigs, they are labor intensive for staff, and I am concerned that as we have continued to repeat the events this year, the popularity has started to wane, not allowing us to match our adoption rates with our intake rates.”