Mecodema oconnori is stenotopic (able to tolerate only small environmental changes). It is adapted for digging, and lives in wet broadleaf, podocarp, or beech woodlands, both lowland and montane.
This shining black beetle is nocturnal, hiding during the day under logs. Its main food is earthworms and small spiders, and it is a slow runner. It gives off an unpleasant smell when disturbed.