Bugraphy of the Vizcacha. 303 
the vizcachas cut down every tall plant they can. 
I have seen whole acres of maize destroyed by them, 
yet the plants cut down were left untouched. If 
posts be put into the ground within range of their 
nightly rambles they will gnaw till they have felled 
them, unless of a wood hard enough to resist their 
chisel-like incisors. 
The strongest instinct of this animal is to clear 
the ground thoroughly about its burrows; and it 
is this destructive habit that makes it necessary for 
cultivators of the soil to destroy all the vizcachas 
in or near their fields. On the uninhabited pampas, 
where the long grasses grow, I have often admired 
the vizcachera; for it is there the centre of a clean 
space, often of half an acre in extent, on which 
there is an even close-shaven turf: this clearing is 
surrounded by the usual rough growth of herbs and 
giant grasses. In such situations this habit of 
clearing the ground is eminently advantageous to 
them, as it affords them a comparatively safe spot 
to feed and disport themselves on, and over which 
they can fly to their burrows without meeting any 
obstruction, on the shghtest alarm. 
Of course the instinct continues to operate where 
it, is no longer of any advantage. In summer, when 
the thistles are green, even when growing near the 
burrows, and the giant thistle (Carduus mariana) 
springs up most luxuriantly right on the mound, 
the vizcachas will not touch them, either disliking 
the strong astringent sap, or repelled by the thorns 
with which they are armed. As soon as they dry, 
and the thorns become brittle, they are levelled ; 
and afterwards, when the animal begins to drag 
