Chicago, for the third year straight, topped Orkin’s rattiest city list. And, yet again, some Chicago public officials came out swinging against dog owners. The assertion is that city rats get fat eating dog poop.
The only problem with these continued claims is that they are not true. Rats do not particularly like to eat dog poop. These public officials are only deflecting the real causes of the problem by blaming dog owners who don’t pick up. Even Orkin’s own technical services director, entomologist Dr. Ron Harrison, explains, “There are many different species of rats. The most common rat in Chicago is the Norway rat. It is native to Asia, where it has evolved to eat a variety of grains and other protein-based foods. In Chicago, Norway rats feed on most things in a dumpster that are grain and meat-based. Norway rats have also been known to pick through animal feces, although it is not their first choice if food is available in a garbage can or dumpster.”
Even if all the dog feces were somehow eliminated overnight from the city, not a single rat would suffer because there are so many other easily obtainable (and preferred) food sources.
“The lay public and the lay media seem to think these questions [about rats] should have simple answers,” says Dr. Bobby Corrigan, PhD Rodentology, Purdue University. “Rat populations in mega metropolises, like New York City [or Chicago] are a complex issue.”
Eliminating rats (even denting their numbers) calls for a multimodal approach.
Here’s more about rats, most of which you probably never thought you’d need to know: When populations get too large and food sources are limited, rather than eating dog feces (they cannot survive on dog poo), they will eat their own young. It’s ingenious, because baby rats are nutritionally sound and because rats limit their own numbers when food becomes scarce by using this harsh but effective strategy.
Of course, picking up after dogs is the responsible thing to do, because the feces can become a public health risk for other dogs and people. But this has little to do with rats. And, I’m unsure why Chicago is the only city that blames their rat problem on dogs and dog owners. In fact, Steve Sullivan, former senior curator of Urban Ecology at the Peggy Notebaert Nature Museum in Chicago, and now director of Hefner Museum, Miami University Department of Biology in Ohio, says he’s never seen a peer-reviewed study to confirm that rats like to eat dog feces.
Why are there so many rats? In part there always are, and due to the increase of infrastructure and building construction, they come out from hiding, so we see more of them. Also, we’ll likely never get rid of all the rats, because, over the eons, Norway rats have evolved to live with people.
Still, rats carry disease. According to the Centers for Disease Control (CDC), in the U.S., they include Streptobacillus moniliformis, or rat bite fever; leptospirosis, a potentially deadly condition that unvaccinated dogs, other wildlife, and people can get and continue to transmit; and salmonella.
Beginning at the age of two to three months, a female rat can produce four to seven litters per year with each litter containing eight to twelve pups. Females can become impregnated within 48 hours after giving birth. The number, size, and survivability of litters produced depends on the amount of food and shelter available. So, among the best means of rat control is to affect their food and shelter.
Experts suggests these means to combat rats:
- Make the rats’ most common food source more difficult to come by. In Chicago, there are thousands of overflowing trash cans without covers, not to mention people who just toss trash into the street or alley. Rats currently have no problem enjoying leftover Chicago deep dish pizza, day-old fruits, or leftover tacos. Food is incredibly easy to find.
The large garbage bins with plastic covers are helpful (because hard plastic covers are better than none at all), but rats are able to chew through plastic. Metal trash bins with heavy metal covers are best, but don’t help much when trash is overflowing and lids are not closed.
- While I don’t endorse the city cut down trees with berries, rats do relish these berries. Homeowners can wash the berries from the sidewalk into a storm drain. Drowned berries don’t taste good.
- Bird seed in feeders attract more than feathered friends; rats really enjoy bird seed. There are “rat-proof” bird feeders available.
- Rats eat pet food left outdoors for pets, so don’t leave pet food outside. If you toss bread outside for the birds in the winter, you can’t be sure if that bread is eaten by birds or by rats.
Make home living tough:
- Trash their homes: Pouring dirt into a rat hole won’t do much. Often, they’ll only dig out. Dry ice, commonly used by stagehands to create an artificial fog effect and by merchants trying to keep perishables from spoiling, also can be deadly to small animals at high concentrations. Some cities were using it, but stopped when animal rights advocates protested. I’m unsure how rodenticides are a better choice, because death is more prolonged when rats are poisoned. And, rodenticides have the potential to be eaten by dogs, cats, and even children. Also, rodenticides aren’t 100 percent effective because once killed, buddies sniff what killed their comrade. If they can ascertain the cause, they actually learn not to ingest the same food. Another means to fill a rat hole is to use concrete mix (using water), and then cover with dirt (remember all exits and entrances must be sealed). If the dry ice or concrete methods are administered in the morning when rats are sleeping, they’ll either never awaken (dry ice method) or they’ll be buried alive (concrete method).
- Rats (and mice) can make their homes inside piled up firewood, and may also snack on it. Firewood should be in an enclosed metal shed.
- Cats and rats aren’t the best of pals—that’s not news. Some cities have programs to relocate cats already spay/neutered and vaccinated against rabies to where there’s a persistent rat problem. The cats move in, the rats move out (or may be killed). This system was successfully in place in Chicago; however, the organization that was known worldwide for their TNR program and “working cat program” had many internal changes (not a single one for the better) causing staff and volunteers to depart, and left them with programs like this one barely hanging on. My hope is that another group in the city will fulfill the need.
And you may be hearing more about all this, because in the fall—when it gets colder in northern climates—is when some rats may seek refuge and try to go indoors. Remember, rats can fit into a hole the size of a quarter.
In the end, there is no one solution for controlling rats. Success lies in a multimodal approach. However, dog feces has nothing to do with the rat problem.