OTHER SOIL ANIMALS - The Soil - page 115

F IG. 39
Newly formed burrow system of a mole introduced into a meadow in the Dutch polders. (Redrawn from J.
Haeck 1969.)
J. Haeck mapped the construction of a burrow system of a mole, introduced into
an unoccupied meadow in one of the Dutch polders, over the course of seven days (it
disappeared after this). The mole dug a total distance of 102 metres in the course of
a week at between 12 and 19 metres a day. Notice how, in Figure 39 , the runs often
went under cow dung which, presumably, the mole could smell some distance away,
and which would attract a concentration of worms and coprophilous insects.
Once a burrow system is established, however, extension will only be necessary
from time to time. In dry or freezing weather, when surface-living worms become in-
active, and burrowing worms retreat to deeper layers, moles will often deepen their
burrows and throw up more mole-hills to dispose of the displaced soil. Mellanby
shows a photograph of a mole-hill forced up through a covering of snow. In light soils,
too, the burrows collapse more readily than in loamy soils, and need more frequent re-
construction. This is particularly the case in heathland or moorland soils where earth-