by movement of a mole or other animal through an undisturbed trace 18 in this regard it is contemplated that the sensor or detector of apparatus 12 could use a non soil contacting sensor or detector operable to detect movement of underlying soil which would be adjusted or tuned so not to signal when inconsequential movements occur as a result of wind rainfall and the like as another advantage by tamping a portion of the soil overlaying a tunnel so as to be at least generally level with the adjacent soil areas then placing apparatus 12 over the tamped portion resting on the adjacent soil actuator 50 will be positioned at a desired consistent elevation above the tamped soil or could be in contact with the soil as desired such that no adjustment of the actuator position is required for use at different locations in this way apparatus 12 is easy to use and can be expected to obtain consistent results if adjustment is necessary or desired the position of actuator 50 can be changed and consistent results will be obtained as long as the soil is prepared in generally the same way and the apparatus is used in the same manner as another possible advantage it is contemplated that utilization of an elongate covering structure.