The Saturday event at the Berman Center for Animal Care in Westland, called "Oh, Rat!" was the organization's first adoption event dedicated to find rats homes, The Detroit News reported.
Three or four families were waiting in line at the adoption event when the center's doors opened at 10 a.m. said Linda Reider, director of animal welfare for the Michigan Humane Society.
Reider said by late morning, five of the 13 rats had been adopted.
Humane Society officials said rats can make good pets.
"They are very friendly," said Kevin Hatman, a society spokesman.
Jesse Stump, 9, agreed. His family adopted two rats, sisters named Thelma and Daphne, that immediately took a liking to Jesse.
"They started biting me," he said. "They started crawling up."