CHICAGO (CBS) — Chicago’s Animal Care and Control (CACC) is warning cat owners, and those who care for feral cat colonies, about a man who’s been out trapping cats.

CACC said the man trapped 15 cats on the South Side on Monday, another 15 on the North Side on Tuesday, and more on Wednesday and brought them all to the city shelter on Western Avenue. The shelter said the man dropped off over 40 cats in total.

The shelter said it is trying to work with him on alternatives to bringing them there, but that he’s adamant on doing just that.

“Many of them do not look injured — many of them look perfectly fine,” said Susan Russell, executive director of Animal Care and Control.

She fears some of the cats brought in might be pets.

The man has been setting the traps himself and bringing them in “to prove a point,” saying the city could do more to keep cats off the street.

Erica Roewade, who’s with the PAWS Chicago Community Cats Department, recently told WBBM Newsradio there are a lot of feral cats around the city.

“Half a million to three quarters of a million free-roaming cats live on the streets of Chicago,” she said. “Honestly from Portage Park and Edgebrook, all the way to the Indiana border, they’re out there.”

The cats brought in are being cared for, but this is adding additional stress to the shelter. CBS 2’s Charlie De Mar spoke with the man bringing them in; he said he plans on setting traps every day and dropping them off.

Animal Care and Control is warning people to keep their cats inside. If your cat has gone missing, click here to view lost pets.