824 MR. W. H. HUDSON ON THE [Nov. 1 9, 



trench a foot or more in depth, and often three or four feet in length. 

 Its use is, as I have inferred, to facilitate the conveying of the loose 

 earth as far as possible from the entrance of the burrow. But after 

 a while the animal is unwilling that it should accumulate even at the 

 end of this long passage ; he therefore proceeds to form two additional 

 trenches, that form an acute, sometimes a right angle, converging 

 into the first, so that when the whole is completed it takes the form 

 of a capital Y. 



These trenches are continually deepened and lengthened as the 

 burrow progresses, the angular segment of earth between them 

 scratched away, until by degrees it has been entirely conveyed off, 

 and in its place is the one deep great unsymmetrical mouth I have 

 already described. There are soils that will not admit of the animals 

 working in this manner. Where there are large cakes of " tosca " 

 near the surface, as in many localities on the southern pampas, the 

 Vizcacha makes his burrow as best he can, and without the regular 

 trenches. In earths that crumble much, sand or gravel, he also 

 works under great disadvantages. 



The burrows are made best in the black and red moulds of the 

 pampas ; but even in such soils the entrances of many burrows are 

 made differently. In some the central trench is wanting, or is so 

 short that there appear but two passages converging directly into the 

 burrow ; or these two trenches may be so curved inwards as to form 

 the segment of a circle. Many other forms may also be noticed,. 

 but usually they appear to be only modifications of the most common 

 Y-shaped system. 



As 1 have remarked that its manner of burrowing has peculiarly 

 adapted the Vizcacha to the pampas, it may be asked what particular 

 advantage a species that makes a wide-mouthed burrow possesses over 

 those that excavate in the usual way. On a declivity, or at the base 

 of rocks or trees, there would be none ; but on the perfectly level and 

 shelterless pampas, the durability of the burrow, a circumstance 

 favourable to the animal's preservation, is owing altogether to its 

 being made in this way, and to several burrows being made together. 

 The two outer trenches diverge so widely from the mouth that half 

 the earth brought out is cast behind instead of before it, thus creating 

 a mound of equal height about the entrance, by which it is secured 

 from water during great rainfalls, while the cattle avoid treading over 

 the great pit-like entrances. But the burrows of the Hare, Arma- 

 dillo, and other species, when made on perfectly level ground, are 

 soon trod on and broken in by cattle ; in summer they are choked up 

 with dust and rubbish ; and, the loose earth having all been thrown 

 up together in a heap on one side, there is no barrier to the water 

 which in every great rainfall flows in and obliterates the kennel 

 drowning or driving out the tenant. 



I have been minute in describing the habitations of the Vizcacha, 

 as I esteem the subject of prime importance in considering the zoo- 

 logy of this portion of America. The Vizcacha does not benefit 

 himself alone by his perhaps unique style of burrowing ; but this 

 habit has proved advantageous to several other species, and has been 



