In addition to the larger and more obvious animals like deer and bear, there are hundreds, thousands, perhaps millions, of microscopic animals like protozoa, nematodes, flatworms, enchytraeids and water bears (a tiny animal living in the water film found on the surface of leaves, mosses, and leaf litter - phyllum Tardigrada).
Research has shown that earthworms can cause changes in the abundance, composition and activity of a whole range of these microscopic organisms through both directs effects of removing the forest floor and mixing it into the upper soil horizons and through indirect effects like changes in nutrient availability.