All animals need to eat to stay alive. For omnivorous scavengers like Rats, what they eat doesn’t really matter. However, they need to eat enough to sustain themselves between meals. We often think of rats as being like mice, just larger. But these rodents have very different eating habits, and these differing habits influence their behaviour in different ways.
Mice need to eat frequently, but they can get by on a minimal amount of food. Mice can literally live off crumbs left behind by people. Because of this, starving mice out is tricky. Rats are a different story, however. They don’t need to feed as often as mice, but they need to eat much bigger meals when they do. Rats can’t go more than four days without food and water. If they have access to water, they can last a bit longer, but they will die within a week at the most. Mice have evolved to take on most of the water in their diets from the food they eat. Rats can’t harness the moisture from their meals nearly as effectively; they need a separate source to keep themselves alive. Easy access to water is an essential consideration for rats when they’re deciding on a nesting spot.
If you find yourself facing down a rat infestation in your home, denying them access to food is definitely a good call. It takes four or five days for a rat to die of starvation, but if they can’t find any food at all, they will usually move on to a new spot before they die. The more active they are, the faster they will dehydrate and deplete their energy reserves, so the less food available, the less active they will be. However, given that they will eat just about anything starving them out is more complicated than it sounds.