An animal trap 106 comprising a trap section having at least one moveable wall (fig 4, 136), to alter the size of the trap section (fig 4. 132) means to detect the presence of an animal within the trap section and to signal their presence to control means, and alter the size of the trap section. The wall may push the rodent through a flap 124 into a collecting means 104. The movable wall may be powered by a motor (fig 4. 142) or a single stroke air compressor (fig 9. 230). The detection means may comprise a beam of light. The moveable wall may be attached to a spring (fig 6. 147) to return the wall to original position, resetting the trap. Other embodiments utilise a pressure sensor to detect a rodent, and a rod and flywheel arrangement or electrical means to move the wall.
