They are about as thick as your finger, and about a meter long. When we walk around our place, you often hear a gurgling sound (quiet freaky the first time you hear it), that is the worm moving about in the soil. The literature says that they are mostly in gullies, but we have them around our land, both in the gullies and in open areas - even more compacted areas.
They are different from the common earthworms, as they don't seem to live in the top soil, but mine the clay (so you wouldn't find them unless you dig a deep hole). The amazing thing is this:
this photo is of a lump of clay that I found while turning over the vegy garden. Its a hard clod, but through it is a tunnel of the giant earthworm, and in it is a worm casting. Can you see the little grass roots in that? The worm is aerating the heavy clay soil, and fertilizing it, allowing grass and other plants to get their roots right down into the deep soil (where the water is). The worm NEEDS to be wet to live, so their presence suggests water. No wonder the native trees are growing at such a rate - with helpers like the giant earthworm, aerating and watering the subsoil for them!!! Since little is known about them, there isn't alot known about how farming impacts them. Obviously ploughing is no good, although shallow ploughing wouldn't probably affect them as they are deeper in the soil. Chemicals are a big issues, and they think this is why they are in low numbers - makes sense why there are many of them here - we don't put chemicals on our land - we don't even use herbicide on the ragwort and blackberries - we do it the 'hard' way - by hand and scythe.
Anyway, it would be interesting to see if there are worms on neighbouring properties, since nearly everyone up here puts out superphosphate (or worse) on their land each year - our place has been 'neglected' apparently.... Just horse/alpaca manure here - and plenty of grass rotting back down.... We have dung beetles, while our neighbour had buy some for their place!!!
