The Earthworm Connection to Terrier Work
The great fierce badger of European folklore -- the animal that is reported to be the hardest nut to crack in the terrier world -- does not slay deer for a meal; it does not even chase rabbits.
No, the mighty badger is mostly a worm eater, with wasps, beetles and beetle larvae, roadkill and plant material supplying much of the rest.
Fox in the U.K. (and to an unknown extent in the U.S.) also derive a surprising amount of nutrition from worms. The mythical chicken-killer is much more likely to be sucking down a worm on a spring or summer night than he is to be raiding a chicken coop.
According to David MacDonald, the foremost fox biologist in the world and the author of the excellent book "Running with the Foxes," earthworms comprise 20 to 35 percent of fox diet in many pasture-rich areas where worms come up in high densities on moist nights with little wind.
Previous studies of fox diet have missed earthworms as a key component of fox fiet because observers did not have night-visions goggles and did not do microscopic analysis of fox scat to find the thousands of tiny chatae which are the scale-like growths that worms use to move through the soil.
Believe it or not, a great deal of the United States was earth-worm free prior to the arrival of Europeans. No native earthworms occured in the northern portion of the continental United States or anywhere in Canada except for a small section along the coast near the U.S. border. This absence of earthworms is believed to be due to Pleistocene glaciations -- probably the same force that limited the range of the American groundhog to the same eastern region earthworms were once limited to.
Approximately 70 species of native earthworms have been described from the eastern United States and another 28 species from the Pacific region. Another 45 imported species of earthworms are now commonly found in various parts of the U.S.-- mostly on the East Coast and in the Midwest and concentrated in areas with disturbed soils (i.e. regularly plowed fields)..
The native range of American earthworms.
Charles Darwin was the first scientist to show that earthworms had a huge impact on soils and postulated that it was the actions of earthworms which explained why so many ancient ruins were now found buried under layers of rich soil.
Darwin's own intererest in worms was sparked by a very long period of observation -- he noticed the flinty rocks found on the plowed surface of an abandoned field he often walked had been sinking into the ground over many years, and that some large stones had even disappeared from view. Studying the phenomenon, he found that the stones had not been moved -- they had simply sunk below the surface of the soil. How did this happen? Darwin decided that the action was due to worms feeding in the dirt below the stones. Stones on the surface had slowly settled into the thousands of worm tunnels that had been dug beneath the stones over time, while millions of loamy earthworm casts had helped bury the stones from the top.
Darwin's last book, The Formation of Vegetable Mould through the Action of Worms, was published in 1881, just one year before his death. Initially published for specialists, the book has achieved some notoriety due to it's emphasis on the the fact that major changes on earth are often the cumulative action of seemingly small things occuring over a very long period of time.
In fact, we now now that soil, if scene through very rapid time-lapse photography, can be seen to virtually boil under the stirring action of worms.
Worms are not the only thing that turn over the soil, of course. Badger, fox and groundhogs often turn over large amounts of soil during their den building as well. In fact, the typical groundhog burrow represents over 700 pounds of removed dirt!
Added to these faunal excavations are prairie dog colonies (once numbering in the millions of individual animals) and ground squirrel colonies (still vast). In Europe and Australia rabbit warrens represent a significant amount of soil tillage.
To read more about how terrier work, terrier breeds and Charles Darwin are interconnected see >> A Pictorial History of Terriers