MILWAUKEE (CBS 58) -- There are some new arrivals at the Wisconsin Humane Society. A single owner surrendered 20 guinea pigs after becoming overwhelmed when they started reproducing at an alarming rate. 

WHS said it's an important learning lesson for anyone who owns guinea pigs. 

"If you have guinea pigs, they do really great in pairs. But you want to make sure that they're the same sex pair, unless you're going to get your guinea pigs spayed or neutered," said Molly McKeown, Wisconsin Humane Society. 

Several guinea pigs have been adopted since, but there are still plenty up for adoption. 

There will be even more guinea pigs available to adopt soon. Some of them require medical treatment and WHS suspects several of the females are pregnant.