I saw my share of victories for cats on Cedar street where I grew up in Pueblo...
Researchers set up cameras in an urban setting to see how cats and rats interacted. And in general, the cats mostly just AVOIDED them.
Over the course of 79 days, the cameras recorded 306 videos where cats had the opportunity to chase a rat. But they only tried to catch them 20 times.
The reason is simple. Most rats are just too BIG for cats the handle. Only TWO rats were killed during the study, and both of them were pretty small.
Cats tend to go for things like mice and small birds that only weigh about an ounce. The average rat weighs about ten times that. Plus, they have bigger teeth and claws, so they're a lot riskier, and harder to kill.
Now, this doesn't mean cats have zero effect. Just having a cat around might make rats AVOID an area a little more. But not necessarily.
Other studies have found cats kill around 4 BILLION birds, and 22 billion rodents a year. Which can devastate local ecosystems. So the researchers say that having a cat around JUST to keep rats at bay might not be a great idea.