CHICAGO (UPI) -- A brewery in Chicago enlisted the help of four feral cats to defend their grain from rats and other pests.

The four cats Venkman, Ray, Egon and Gozer were brought in to Empirical Brewery in December to help keep the brewery's pest problem under control.

"The traditional rodent control solutions weren't working for us, so we turned to Cats at Work," the brewery's website states. After a brief acclimation period, the cats were free to roam around the brewery.

Empirical Brewery brought the cats in from Tree House Humane Society and offered them a home in exchange for their work.

"We built them a house, we feed them, we change their litter and in exchange they offer the best pest control solution around," they wrote.

According to an FAQ, the cats help to protect the sterility of the grain and ultimately the integrity of the brewing process.

"Our grain is stored in heavy sacks, which the cats protect from rodents but never eat themselves. From the grain crusher, to the grist case, to the mash tun, to the boil kettle, to the fermenter, to the bright tank, everything is part of a closed system," the post states. This is necessary to maintain a nearly sterile environment for the yeast to properly ferment the beer without bacterial interference.

Venkman, the head brewery cat, also has his own Twitter account which chronicle's the cat's adventures.

Copyright 2016 by United Press International