How common are mutations?
Virtually everything on the Blasted Earth has some odd mutation or genetic change be it man, alien, plant, or animal. Somethings are simply alien life forms. Keep in mind we have the created-designer animals mostly they have weird abilities often specific to the society that created them. Cats that can blend in with designer curtains and carpets stand out in the jungle. Pet rabbits that emit light in certain frequencies so they stand out against the blue walls of some household that has not existed in 300 years. These designs should have a specific purpose even if those purposes are no longer valid. A bunny that glows orange with a refraction mutation may be presented to the party as they pass by an open field. The unlucky character who decides to take a pot shot finds the fire bounces back from the hapless bunny and fries the character who fired the shot. By way of example.