Differences in burrowing behaviour and spatial interaction between the two earthworm species Aporrectodea nocturna and Allolobophora chlorotica

To study intraspecific and interspecific interactions between different ecological types of earthworm, the burrowing behaviour of two earthworm species (the anecic earthworm Aporrectodea nocturna and the endogeic earthworm Allolobophora chlorotica) was observed in a microcosm. Earthworms were either alone in the microcosm, together with a conspecific earthworm, or with an earthworm of the other species. Observations under red light, including those of the position of the animals and the burrow dug, were recorded 4 times a day for 8 days and provided the data needed to reconstruct the probable trajectories of each earthworm. Differences in movement and burrowing behaviour were observed. Comparisons between the two species confirmed the expected behaviour of each ecological type: A. nocturna reused its burrow system regularly, whereas A. chlorotica rarely did. Moreover, it was shown that A. chlorotica burrowed less and explored a smaller surface when in the presence of A. nocturna. Besides, A. nocturna burrowed less and explored a smaller surface when in the presence of another A. nocturna. If these interactions occur under natural conditions, they could affect the structure of the burrow systems of the earthworm species examined.