In September 1983, nuclear weapons fell across the planet, many thousands of cities and towns were destroyed and the surviving humans evacuated huge areas and escaped to 'safe' areas. In their wake, they left many animals some of which were domesticated, like pet cats and dogs, and some not so domesticated. In the United States, the craze of the late 1970s and early '80s was to own large exotic pets, tigers, lions and other big cats were kept in backyards across the country. After Doomsday many escaped, survived and reproduced.