The rabibunny village is constantly harrassed by mutants. For this reason, they offer Twinsen to open the Door of the Sacred Carrot if he destroys the mutant factory. Twinsen then disables the factory by killing the green eggs that he finds there. From then on, the mutants are stopped from being manufactured, but a lot of them still remain in the Northern Hemisphere. Twinsen encounters some more mutants in Tipett Island.
There is no mention of mutants in LBA2.