Endogeic earthworms live and burrow in the soil to find their food. They burrow by pushing the soil aside or
ingesting it and are thus sensitive to soil compaction. However there is a scarcity of data regarding the effects of
soil bulk density on the burrowing behavior and activity of endogeic earthworms. We carried out laboratory
experiments using repacked soil cores with various levels of bulk density (from 1.18 to 1.38 g cm 3) in which
individuals of Aporrectodea caliginosa or Allolobophora chlorotica were incubated for six weeks. The burrow
systems inside the soil cores and the compaction around the burrows were then analyzed using X-ray tomography.
Soil water infiltration measurements were also carried out. The increase in bulk density had a negative
impact on all burrow system characteristics (length, volume, diameter, continuity, number of burrows). When
bulk density increased from 1.18 to 1.38 g cm 3, volume, diameter, continuity and the number of burrows
decreased on average by 77 %, 21 %, 81 % and 58 %, respectively. The increase in density due to compaction
around the burrows was similar whatever the species and the bulk density. Increasing soil bulk density from 1.18
to 1.38 g cm-3 also greatly decreased water infiltration ( 89 % for both species) and increased breakthrough time
(10 and 25-fold for A. chlorotica and A. caliginosa respectively). However, compared to a control without
earthworms, water infiltration in cores incubated with endogeic species was only increased significantly at 1.18
and 1.23 g cm 3. This illustrates that burrows made by endogeic earthworms moderately increase water infiltration
and only when the soil bulk density is low. Data provided in this study could be used to refine simulation
models of earthworm burrowing behavior where burrowing is assumed to be mainly governed by soil water
content, temperature and soil bulk density.