Rats have for centuries been one of the most hated species on the face of the planet. The main reason being that people tend to see them as a sign of dirty conditions and diseases, which they are notorious for transmitting. In fact most people are more concerned with the eradication of rats altogether than learning anything about them. As a result many people tend to overlook the rat and how it is in fact an important species in many ecosystems and food chains.
Famously rats have a very varied diet that includes a scavenged food, insects and carrion. They thrive on human waste and discards, and as such can be found wherever humans gather. It is said that in human settlements you are never more than 50 feet away from rats, and that there are 25 rats for every human on the planet. Which puts their numbers at approximately an impressive 175 billion individuals. Rats are not however at the top of their natural food chains, and they indeed have many predators that thrive because they thrive.
Weasels, ferrets and several other members of the polecat family are the main natural predators of rats. Despite some of them being smaller than rats, they will aggressively hunt down and kill all rats that they encounter, often more than they can eat even. Farmers in some countries have for hundreds of years paid for trappers to catch them live weasels or minks and release them in their barns. After which all the rats that previously made their homes in there would be killed, and the scent of the predator would keep them away for several months afterwards.
Because rats will often stray into the open in order to reach food, several predatory species of birds will also take rats from time to time. When caught in the open rats have no defence at all against predatory birds, who can pick them out and grab them with their talons with ease. As rats tend to predominantly stay either underground or out of the open however, this isn't generally to a great amount.
In tropical climates many of the larger predatory insect species will also feed on rats as part of their staple diets. These include tarantulas, giant centipedes and scorpions, which usually kill rats by way of venom rather than with teeth or claws. These types of large invertebrates would not normally feed on rats in any great number, but often they are easier and more numerous than their natural prey, particularly near human populations.
Another major predator of rats is snakes of a number of different species, who seem to be particularly adept at catching and killing them. Many snakes feed almost exclusively on rats and similar small mammals, and because rats are often the most numerous, they are also the most commonly consumed. So much so in fact that there is even a species of snake called the rat snake. Also in some parts of the world snakes are introduced into rat nests as a means of pest control to kill off rats nesting in or around buildings.
The common domestic cat is one such predator and will commonly hunt and kill rats, although more often as a natural instinct than borne out of a need to survive and feed themselves. It dies have to be said that although cats populations are artificially higher then they might be naturally due to people having them as pets, their predation on rats is not numerically significant. The reason being that cats are much more likely to hunt smaller prey such as common garden birds, frogs or mice. Which as well as being easier to catch, put up less of s fight than rats.