The importance of earthworms for soil functioning is widely accepted and is mainly linked to their burrowing, feeding and casting behaviours. However, our knowledge of earthworm behavior is still limited by the lack of efficient and easy-to-use methods. In this work, we describe and test a new marker of earthworm bioturbation. Dense particles of tungsten, visible in X-ray images, were located at a certain depth in repacked soil cores inoculated by either Lumbricus terrestris or Aporrectodea caliginosa, alone or in combination. This marker was compared to the classical luminophore method (i.e. colored sand particles) generally used in aquatic ecology. The dynamics of both the burrow systems and the casting activities was followed using X-ray tomography every two weeks for a period of 10 weeks. Below ground casting activities could be assessed since parts of the casts excreted by the earthworms were marked by tungsten and appeared white in the images. The time dynamics of both burrow and cast productions were almost linear and significantly influenced by the earthworm species and the presence of litter. As expected, L. terrestris created larger (up to 50 cm3) and deeper burrow systems and made fewer macropores compared to A. caliginosa. Surprisingly, both species were equally influenced by the presence of litter, and this highlighted their behavioral plasticity. For example, A. caliginosa decreased by 32 % the volume of burrows in the presence of litter and the resulting burrow system was significantly shallower which showed that this endogeic species is indeed able to partly feed on surface litter. The use of tungsten particles is a promising new tool to accurately characterize the casting activities of earthworms in the soil and to study behavioral plasticity under the influence of environmental factors.