In the 1972 sci-fi horror film "Night of the Lepus", what is the threat that needs to be eliminated?

The American film "Night of the Lepus" deals with giant mutant rabbits that developed from an experiment that was meant to control a local rabbit population around a town in Arizona. One test subject rabbit that was given an experimental drug by the researchers Roy and Gerry Bennett (portrayed by Stuart Whitman and Janet Leigh) was switched with an uninjected control subject and is given to their daughter Amanda (Melanie Fullerton). The injected rabbit escapes and shortly afterward mutilated bodies begin to be found around town.

Explosives are found not to affect the growing population of mutant rabbits, their terrorizing spreads farther to other nearby towns. A plan to trap the rabbits by herding them using car lights and a large electrified fence, followed by machine gun fire, ultimately stops the rampage of the rabbits.

The cast also included Rory Calhoun, DeForest Kelley and Paul Fix. The film was savagely criticized for its poor special effects, lackluster acting and the overall premise that rabbits could be made to be terrifying. It is now considered a cult film.