Associated with earthworm enclosures is a novel method (“tunnel” trapping) that can be used to observe and record emigration of earthworms. Trap units can be combined with earthworm fencing in the field [24], or with mesocosms in laboratory experiments allowing examination of emigration rates, while manipulating biotic and abiotic factors (e.g., population density, community structure, predation, resources availability, temperature, precipitation).
Tunnel traps can be prepared using 1 litre plastic pots with mounted needle-perforated lids. Holes ( mm) drilled in these smaller “capture pots” just below the lid allow insertion of PVC tubing (10 mm ID, 5 cm long) to connect to either earthworm fencing in field enclosures or larger soil-filled mesocosms. Surface migrating species can move from enclosures/mesocosms into traps via the tubing that is aligned at the soil surface (Figure 2). Movement of captured individuals back into containers is prevented by filling capture pots with soil or other suitable medium to half of their total volume. Providing acceptable conditions (e.g., soil and food) in capture pots can allow earthworms to survive for long periods therefore permitting relatively infrequent examination. Tunnel traps have been successfully used in both field and laboratory experiments which aimed to examine dispersal of the anecic L. terrestris as affected by population density and resources availability