Chernobyl mutant rats - myth or reality

Anyone familiar with a school biology course is also familiar with the concept of mutation. Recall: mutation is a persistent and inherited change in the genotype that occurs under the influence of factors of the internal or external environment. That is, the mutated organism will pass on its altered gene pool to its descendants. Making the body mutate is quite difficult, but in nature, mutation takes place much more naturally and efficiently.
Most of the animals and plants-mutants are simply defective living organisms with poorly developed groups of organs or with certain oddities in appearance. For example, the Internet is full of photos of two-headed bulls, humpback cats and tailless dogs, kittens without a paw, or, conversely, with an additional one. Of course, the immunity of such animals does not compare with the immunity of healthy individuals, and therefore the chances of survival for mutants are extremely low. Which, in principle, is natural and prudent from the side of nature: thanks to natural selection, the mutation does not spread everywhere, but remains within the framework of one generation, which dies without leaving offspring.
The main characters of children's cartoons, famous superheroes like Spider-Man or the Hulk, are essentially the same mutants. If you believe the cinema, a person can be made to mutate by factors such as the bite of an animal, a special vaccine or a radioactive substance. However, this is only a fantasy of the directors, since in reality such metamorphoses are hardly possible.
Rumors about Chernobyl rats, supposedly the size of an average dog, for example, here: http://www.otpugiwateli.ru/krisi_mutanti.php - absolutely the same speculation, only not directors, but eyewitnesses and journalists. Moreover, if the latter are simply making money on sensations, those who report such cases to the newspaper really see huge animals. True, all encyclopedias recognize them as normal: the body of a rat, in fact, can reach 40 centimeters in length, weighing more than 1000 grams, which, you see, looks very impressive. Add to this the familiar proverb "fear has big eyes" and you get the end result, a rat the size of a cocker spaniel.
However, it would be unfair to say that giant rats do not really exist. Exists. True, only in Africa, and they eat exclusively grass, but this does not prevent the fans of sensations from uploading their photos under horrific headlines about new types of Chernobyl mutations. Do not fall for provocations, ordinary rats will not harm you at all.
However, any rats will run away from an ultrasonic repeller, for example, from Tornado 400: http://www.otpugiwateli.com/new400.html