Introduction

The official motto of Chicago is Urbs in Horto, which translates to “City in a Garden”, but it can also be described as a city overrun with rats. The pest control company Orkin has ranked Chicago as the rattiest city in the United States for nine years in a row. I worked for two years as a pest control technician and I oversaw the rodent control program for the Village of Niles in the summer of 2023. I’m also certified by the Illinois Department of Public Health for general use and restricted use pesticides. I have extensive, firsthand experience working with rodenticide baits to control rats and I saw the worst of the problem as a pest control tech in Chicago. The rat problem in Niles is a more recent phenomenon and not nearly as severe as it is in Chicago, though the drivers are the same.

The Problem (and why it’s so hard to get under control)

The Chicago rats we’re familiar with are Norway rats (Rattus norvegicus), a non-native species adapted to living in close association with humans in urban environments. This species has other common names like brown rat, sewer rat, and street rat, but I’ll refer to them as Norway rats here. Norway rats are almost entirely dependent on humans for food, water, and shelter; large cities like Chicago provide a near perfect environment for them to not only live but to thrive. The main driver of the problem is poor sanitation on the part of residents. This is common knowledge in the pest control industry and I experienced this almost daily while doing field work in Chicago, and to a lesser extent while working in Niles. Norway rats have food preferences but they are best described as omnivorous. Some of the contributing food sources I encountered while working in Chicago and Niles include dog feces, spilled bird seed, home grown garden vegetables, and fruit from fruit trees. This problem is simultaneously easy to remedy (remove the food sources the rats depend on) and intractable because of Chicago residents who don’t practice good sanitation and inadvertently feed rats and contribute directly to the problem. Throw in poor garbage disposal and you have a perfect storm of conditions that are responsible for the ongoing infestation.

Rodenticide Baiting as a Means of Pest Control

Rodent control bait boxes (click to see the larger version)

A common method of controlling rats is to use boxes that contain rodenticide baits. You’ve probably seen these bait boxes and wondered what purpose they serve (and they’re hard to miss if you live in Chicago). Bait boxes are small, black or gray plastic boxes placed around the perimeters of buildings and other structures. Some of these boxes are shaped like rocks to blend in better with landscaping (the photo at right shows two such boxes). They have two holes, one on each side, that allow rats and other target rodents to enter and eat the poison laden bait inside. The only purpose of bait boxes is to hold rodenticide baits. They’re designed, as best as humanly possible, to keep people and dogs from accessing the bait, since the bait is harmful to any mammal that consumes it. The boxes are locked and can only be opened for servicing with a special key. This method of rodent control is inexpensive, easy to set up, and easy to maintain. More importantly, a bait box program covers a large area. When I worked for a pest control company in Chicago and for the Village of Niles, part of my job involved setting up and servicing these bait stations for our clients. I would determine where the best locations for placing the stations were, fill the stations with bait, and on return visits replace missing or old bait with fresh bait. The bait consists of a food attractant and a very small amount of poison. The poison is an anticoagulant that interferes with blood clotting and leads to death through uncontrolled bleeding. This use of anticoagulant baits is effective in killing rats and other target rodents, something I witnessed while working in Chicago and Niles. We also used old fashioned mechanical snap traps for rat control but snap traps are more labor intensive and messier to work with.

Drawbacks

The drawbacks of using anticoagulant baits to control rats are twofold. First, though effective, rodents eventually develop resistance to the baits, rendering them useless and requiring the development of new baits. We were using a second generation anticoagulant bait in Niles because rats had developed resistance to the first generation of baits. This is a common and recurring problem in pest control — companies develop poisons, the use of these poisons puts enormous selective pressure on target pests, because of the variation in the populations of these target pests some resist the effects of the toxins, these animals survive, reproduce, and pass along their resistant genes to their offspring. It’s a vicious cycle, and an inelegant way to control pests.

The second, more insidious effect is secondary poisoning of non-target animals. Predators like hawks and owls that consume poisoned rats take in some of the poison and become poisoned themselves. This is a well documented phenomenon and I won’t get into the details of it here. This article from the National Park Service offers a good overview of the problem — Avoiding Unintentional Poisoning.

Banning Rodenticide Baits Won’t Work

I’ve heard talk of moving to ban rodenticide baits. Despite their shortcomings, these products work well at controlling rat numbers; without them, or an effective alternative, Chicago’s rat problem would be even worse. Such a ban would face stiff opposition from the many pest control companies that operate in the Chicago area and who depend on rodenticide baits for their business. Opposition would also likely come from the Chicago municipal government, since the City uses rodenticide baits as part of its own rodent control program.

Challenges and Possible Solutions

Using rodenticide baits to control rats only addresses the symptoms of the problem and not the underlying causes, which are usually sanitation issues. Getting enough people to clean up after their dogs, clean up spilled bird seed, pick up fallen fruit from their fruit trees, and address other contributing factors is a tall order, especially in a city as large as Chicago. Proper sanitation would reduce the need to use rodenticide baits to control rodents, reducing the incidences of secondary poisoning of wildlife. This isn’t difficult to understand but getting everyone, or at least enough people on the same page won’t be easy. Hiring a pest control company to set up a baiting program to control rats is easier, which is why so many landlords and property management companies choose this option.

So what can be done? If we’re going to change behaviors we need to start with ourselves and work outwards. Be part of the solution by not contributing to the problem. Practice good sanitation on your own property. Talk to your friends, family, and neighbors about the connection between poor sanitation, the use of rodenticide baits, and secondary poisoning of wildlife. Here are some tips to keep rat numbers down and lower the chances of incidental poisoning of non-target animals and people.

• Clean up dog waste in your yard and don’t let it sit overnight. Rats love dog poop.
• If you have bird feeders, clean up spilled bird seed or install a screen underneath the feeder to catch the seed before it reaches the ground.
• Consider removing your fruit trees or at least don’t leave fallen fruit on the ground.
• Consider removing your garden vegetable plants and don’t let the vegetables stay on the plant longer than necessary. You might also consider installing fine wire chicken mesh around the plants to make it harder for rats to access the vegetables.
• Rats need standing water to drink. If you have an unprotected koi pond, rats will drink the water. Consider removing the koi pond or installing fine wire chicken mesh around it.
• Properly dispose of your garbage. Poor garbage disposal is a big problem in Chicago and a driver of our rat problem. To illustrate this point, I once found whole lobster tails in an alley behind a building in the Loop my company had a contract with. Lobster tails. Chicago rats are probably eating better than most of its human residents, which is why the rats are thriving. Make sure your garbage cans have tight fitting lids, don’t let garbage bags spill out of the can, and make sure rats haven’t chewed holes in the plastic cans to access food (they can and will do this).
• Don’t ever use OTC rodenticide baits for personal use. You might kill rats but you’re just as likely to kill native wildlife like chipmunks and squirrels and you could harm or kill pets. I saw this firsthand while working in Niles.
• Don’t ever use anticoagulant rodenticide baits for personal use. You can buy these products online from Amazon and you don’t need a license or certification. Try it yourself. Go to Amazon and do a search for First Strike soft bait. This is the same product we used in Niles when I worked for the Village government overseeing its rodent control program. This and similar anticoagulant rodenticide baits are dangerous and heavily regulated by the government. If you don’t know what you are doing you could harm or kill native wildlife, pets, and people. The criminal penalties for misuse of these products are severe.

A broader, large scale education program similar to Cats Indoors might be worth considering. Such a program could emphasize the connection between sanitation, the use of rodenticide baits, and the effects these baits have on wildlife. If it reaches enough people it could change behaviors and lead to a decrease in rat numbers and less need to use rodenticide baits.

Final Thoughts

This isn’t an easy problem to solve. As I try to emphasize here, getting enough people on the same page is the biggest hurdle. I’m probably being overly optimistic about the chances of success but addressing the underlying cause seems to be the first place we should start.

Structural Pest Control Certification