On 2007-12-20 09:17:16 +0000, David in Normandy said:

We've got lots of normal mole hills in the "lawn", but the
other day a solitary mole hill appeared away from all the
other hills, that was double the size of all the others. I
raked all the earth away and onto a flower bed exposing a
hole about 2 inches diameter going into the ground at a
steep angle. I poured a container full of old cooking oil
down the hole. Today there is another large hill above the
same hole.

Is this a mole or some other burrowing rodent? I've not
seen moles attempt to make "a mountain out of mole hill"
before. Perhaps this is an ordinary mole aiming for some
sort of construction record for the largest hill?
Sounds like Mother Mole to me. She's the one who owns your lawn and
stops other moles from taking up residence. She typically lives apart
from her offspring and makes fewer but bigger excavations. You can
target her but if you succeed, another matriarch will move in.