302 The Naturalist in La Plata. 
its very slow rate of increase, and yet see them in 
such incalculable numbers. The female has but one 
litter in the year of two young, sometimes of three. 
She becomes pregnant late in April, and brings 
forth in September ; the period of gestation is, I 
think, rather less than five months. 
The vizcacha is about two years growing. A 
full-sized male measures to the root of the tail 
twenty-two inches, and weighs from fourteen to 
fifteen pounds; the female is nineteen inches in 
length, and her greatest weight nine pounds. Pro- 
bably it is a long-lived, and certainly it is a very hardy 
animal. Where it has any green substance to eat 
it never drinks water; but after a lone summer 
drought, when for months it has subsisted on 
bits of dried thistle-stalks and old withered grass, 
if a shower falls it will come out of its burrows 
even at noonday and drink eagerly from the pools. 
It has been erroneously stated that vizcachas 
subsist on roots. Their food is grass and seeds; 
but they may also sometimes eat roots, as the 
eround is occasionally seen scratched up about the 
burrows. In March, when the stalks of the peren- 
nial cardoon or Castile thistle (Cynara cardunculus) 
are dry, the vizcachas fell them by gnawing about 
their roots, and afterwards tear to pieces the great 
dry flower-heads to get the seeds imbedded deeply 
in them, of which they seem very fond. Large 
patches of thistle are often found served thus, the 
ground about them literally white with the silvery 
bristles they have scattered. This cutting down 
tall plants to get the seeds at the top seems very 
like an act of pure intelligence; but the fact is, 
