The heavy steel base (3), placed on a levelled mole-hill, vents the mole-tunnel through a large hole surrounding the gun muzzle, on which a detector cone (9b), with a permanent magnet collar (9a) freely slides. The mole, resealing the tunnel, throws up more earth, lifting the detector till the magnet closes a proximity switch (9). The firing unit (13) then passes (15,7a) a current pulse, via the breech-block (2,2a), through an igniter (7) in a cartridge (6) loaded in the barrel (1). The shot discharged, or the shock-wave, kills the mole.Safety features inhibit firing if the device is tilted, or lifted, or if a rain-shield is not closed. The shield incorporates operation indicators, and, with a perforated metal enclosure (4), screens against electromagnetic interference.