In reality these animals are not related to rodents although there is a distinct resemblance.
Determining the species from which the Zone's rodents developed has so far proved impossible although it can be said with certainty that their ancestors were gregarious mammals. Reaching up to 40cm at the shoulder they are more mobile, aggressive and ravenous than the normal desert animal.
Mutant rodents live mainly in basements and destroyed buildings feeding on everything they can get their teeth in, from plants to careless stalkers. Sometimes rodents attack and kill big animals and mutants in a large group tearing them apart before they can escape.