A trap for exterminating pests, preferably rats in sewers, said trap comprising: a trap housing and a bait mechanism. The trap also has a trigger mechanism capable of detecting the presence of a rat and releasing a killer mechanism when the rat is within the total range of the killer mechanism； and a trapper mechanism capable of detaining an animal. The trap may also convey a killed animal from a first position, in which discharge of the killed animal will not entail that it is conveyed away by water running through the sewer, to a second position, in which discharge of the killed rat will entail that it is conveyed away by water running through the sewer.
