92 MAMMALIA 



damage they do. The annual export of approximately 3,000,000 rabbits 

 valued at about 70,000 and of some 8,000,000 skins valued at about 

 115,000 is all the return they give, but it only represents a small 

 proportion of the dimensions of the pest. In all parts where rabbits 

 abound, their destruction entails a heavy expense on the occupiers 

 of the land. There are no data available anywhere to enable one to 

 estimate how many rabbits are destroyed every year, but far more 

 are killed by phosphorus than by trapping. The latter method alone 

 furnishes any statistical data, the former is an unknown quantity, 

 but it represents a very large figure. 



Probably the most ghastly exhibition of the work of rabbits is to 

 be found in the grass-denuded districts of Central Otago, parts of 

 which have been reduced to the condition of a desert. It is improbable 

 that this state of affairs could have been brought about by rabbits 

 alone. Before their advent, the runholders who had possession of 

 the arid regions in which the rainfall probably averages 10 to 12 

 inches annually, and certainly never exceeds 15 inches were doing 

 their best to denude the surface of the ground by overstocking with 

 sheep and frequent burning. The latter was resorted to because many 

 of the large tussock-forming grasses especially such as the silver- 

 tussock, Poa ccespitosa yielded coarse and rather unpalatable fodder, 

 but after burning the tufts, a crop of tender green leaves sprung up, 

 which were very readily eaten. Unfortunately the burning not only 

 got rid of most of the coarse growth of the tussocks, but it also swept 

 off the numerous bottom grasses which occupied the intervening 

 spaces, such as Agropyrum scabrum, Danthonia Buchanani, Danthonia 

 semiannularis, Triodia Thomsoni and Festuca ovina, which were the 

 mainstay of the depasturing flocks. Even before the rabbits arrived 

 the work of denudation of the grass-covering had been proceeding 

 apace through the causes mentioned. Thus Buchanan, writing in 

 1865, said: "it is no wonder that many of the runs require eight 

 acres to feed one sheep, according to an official estimate." Mr Petrie 

 thought this an unduly severe estimate, "as in the mid-seventies 

 the sheep-runs of Central Otago were reputed to carry at least one 

 sheep to four acres, and the majority of them carried one sheep to 

 three acres or somewhat less." 



Mr Petrie, who reported to the Department of Agriculture on 

 the grass-denuded lands of Central Otago, knows more about this 

 subject than anyone else, and I quote him at some length : 



Before the rabbit-invasion began the hill-slopes carried a fairly rich 

 and varied covering of tussock and other grasses, and, except on the steeper 

 rock sun-baked faces, had not been very seriously depleted even in the 

 early nineties. The earlier stages of this depletion may now be seen in 



