DENVER -- Cuddling inside Colorado barns and standing watch in stables, hundreds of feral cats are on their second lives.
"The working cats program is a great way for us to find homes for cats that may not have been adoption candidates a few years ago," said Joan Theielen, with the Dumb Friends League. "Their job is to help with pest populations, so things like mice or rats you might have on your property."
The cats act as an environmentally-friendly form of rat or mouse control.
The Dumb Friends League launched the program in 2012, and it has been growing fast. Last fiscal year, the organization reported that 406 working cats were adopted to good homes.
"They may not be lap cats or very cuddly, but we have caring owners that will provide them with a home outdoors. With a job and they can be really successful," said Theielen.
A similar program has also seen success in large cities such as Chicago, where feral cats are being used to attack rat problems in backyards and even breweries.
"Before we got the cats, we used to have rodents," Nevin McCown, the Head Brewer with Empirical Brewery told CNN. "Every once in a while, I would discover little holes that had been scratched in bags of grain, and you know what I have to do with that, I have to throw it out...They keep my grain safe."
In Denver, the Dumb Friends League spays and neuters the working cats, gives them their vaccinations and microchips them.
"We have 15 cats available for adoption right now and the adoption fees are waived," said Theielen.
Owners must require a safe, warm place for the cats, as well as food, water and veterinary care.