Yes, rats eat cockroaches. Both wild and domestic rats are opportunistic omnivores that readily hunt and consume roaches when they encounter them. Cockroaches are a natural part of the diet for many rodent species, providing a protein-rich food source that rats will actively pursue.
Why Rats Hunt Cockroaches
Rats are not picky eaters. They’ll consume nearly anything with caloric value, from grains and fruit to insects, carrion, and garbage. Cockroaches fit neatly into this diet because they’re abundant in the same environments rats inhabit: kitchens, basements, sewers, and outdoor spaces near human activity. When a rat spots a roach, it will chase and catch it. Rats are fast, agile, and well-equipped to handle prey of that size.
Cockroaches offer genuine nutritional value. Analysis of the American cockroach shows roughly 9% crude protein, nearly 18% crude fat, and over 21% fiber. For a rat foraging in an urban environment, a roach is a calorie-dense snack that’s easier to catch than many other prey items. That said, cockroaches are a supplement to a rat’s diet, not a staple. Rats primarily rely on plant-based foods, stored grains, and human food waste. Roaches fill gaps when other food is scarce or when the opportunity presents itself.
Which Rats Eat Roaches Most Often
Brown rats (the common city rat) and black rats both eat cockroaches, but the behavior is most frequent in environments where both species overlap. Urban settings, restaurants, apartment buildings, and sewers create ideal conditions. Wild rats living outdoors also eat roaches when they find them, though they may have more diverse insect prey available.
Pet rats will eat cockroaches too, and some owners occasionally offer feeder insects as enrichment. Rats in laboratory settings have been observed consuming cockroaches with no hesitation, confirming the behavior isn’t limited to desperate or starving animals. It’s simply part of being an omnivore.
Parasites Transmitted Through Roaches
Eating cockroaches isn’t without risk for rats. One well-documented danger involves a parasite called a thorny-headed worm (Moniliformis moniliformis). Rats are the primary host for this parasite, and cockroaches serve as the middleman in its life cycle. Here’s how it works: an infected rat sheds parasite eggs in its droppings. Cockroaches and beetles feed on those droppings and become carriers. Inside the cockroach, the parasite develops into an infective stage over 6 to 12 weeks. When another rat eats that infected roach, the parasite latches onto the rat’s intestinal wall using a barbed “thorny head,” matures into an adult worm, and starts the cycle again.
This cycle is so well-established that scientists consider the rat-cockroach-rat transmission loop a textbook example of parasite life cycles. In areas with heavy rat and roach populations, the infection rate can be significant. The worms cause intestinal inflammation and can affect a rat’s overall health, though they rarely kill adult rats outright.
Bacterial Risks From Cockroach Prey
Cockroaches are notorious carriers of harmful bacteria. They crawl through sewage, garbage, and decaying organic matter, picking up pathogens along the way. Salmonella and other bacteria that cause gastrointestinal illness have been isolated from cockroach bodies, legs, and gut contents. German cockroaches in particular have been experimentally linked to spreading Salmonella Typhimurium, a common cause of food poisoning in both animals and humans.
When a rat eats an infected cockroach, it can pick up these bacteria. Rats themselves then become carriers, shedding the bacteria in their droppings and spreading contamination to food preparation surfaces, stored food, and water sources. This chain of transmission is one reason why buildings with both rat and cockroach infestations pose a compounded health risk. The two pests essentially amplify each other’s ability to spread disease.
Do Rats Control Roach Populations?
It’s tempting to think rats might serve as natural roach control, but the reality is less helpful. A single female cockroach can produce hundreds of offspring in her lifetime, and roaches reproduce far faster than rats can eat them. Rats pick off individual roaches opportunistically, but they don’t hunt them systematically enough to make a dent in an established colony.
In fact, the relationship tends to work in reverse. Buildings with rat problems often have roach problems too, because the conditions that attract one (food waste, moisture, shelter, poor sanitation) attract the other. Rat droppings even provide food for cockroaches, creating a feedback loop where each pest supports the other’s population. Addressing one infestation without tackling the other typically leads to limited results.
What This Means for Pest Control
If you’re seeing both rats and roaches in your home or building, treating them as a single problem is more effective than targeting each separately. Eliminating food and water sources hits both species. Sealing entry points reduces access for rats, while removing clutter and organic debris takes away cockroach hiding spots. Bait stations designed for one pest can sometimes interfere with the other. Rat poison, for example, can be consumed by cockroaches, though it’s not an effective roach treatment.
One practical concern: if you use roach bait stations, rats may eat the bait or disturb the stations. Placing roach baits in areas rats can’t easily access (inside wall voids, behind appliances flush against walls, or in narrow crevices) helps ensure each treatment reaches its intended target.