Papers. 19 



PAPERS 



1. Some Effects oj Imported Animals on the. Indigenous Vegetation. 

 By B. C. Aston. F.I.C. F.C.S. 



[Bead before the Wellington Philosophical Society, 10th May, 1911.] 



The Tauherinikau Valley is portion of a public-works reserve, and extends 

 from the mouth of the gorge near Featherston for some twelve miles in a 

 northerly direction. The valley is a natural fastness into which man seldom 

 penetrates. Bounded on all sides by mountains of 1.500 ft. or more in 

 height, the only outlet for the river bemg a trackless gorge, the valley has 

 become a sanctuary for escaped cattle, wild pigs, and rabbits. On either 

 side of the river, which is comparable with the Hutt in size, are extensive 

 gravel-flats covered with light scrub, chiefly Leptospermum (manuka), fre- 

 quently broken by patches of good grass land on which Yorkshire fog, red 

 and white clovers, and cocksfoot ffcr 1 excellent pasturage for cattle. In 

 January, 1910, one herd of eleven, which allowed one to approach closely, 

 was seen. Along the narrower and higher portions of the valley, where the 

 forest closes into the stream, tracks have been made by the cattle in all 

 directions. It is probably from this valley that they have gained access 

 to the Mount Alpha portion of the Tararua Range above the bush-line. 

 On this high country the effect of the cattle is most readily observed. Well- 

 beaten tracks have been made along all the main ridges from the Quoin 

 (3,900 ft.) to Mount Alpha (4,600 ft.), and thence, to the south side of Mount 

 Hector, approaching almost to the summit. No tracks were observed on 

 the Otaki side of Mount Hector. On the slopes of Mount Alpha nearly 

 every plant of Ligusticum dissectum T. K.* had been closely cropped, from 

 which it appears that this succulent umbellifer, which is one of the most 

 abundant and characteristic plants of this range, will disappear where the 

 cattle are able to reach it. No good argument can be adduced for allowing 

 the cattle to remain. Being so tame they will not provide sport ; of the 

 Hereford breed, they are not so picturesque as, for instance, Highland 

 cattle would be ; and, although as track-makers they have done some 

 good work, further toleration of their existence is likely to result in a perma- 

 nent alteration of the flora, which, from the proximity to Wellington City, 

 should be preserved intact. The effect of the depredations of pigs is every- 

 where noticeable in the valley, both in the forest and on the manuka flats 

 and grass lands, where in the aggregate large areas have been turned over. 

 On the valley-flats a fine patch of the rare orchid Gastrodia sesamoides had 

 been destroyed. Gastrodia Cunninghamii, with its large underground tubers, 

 now fairly common in the Tararua forests, is likely to become very rare. 

 On the high bushed spurs, where well-defined tracks have been worn, the 

 most noticeable objects of the attentions of pigs are the species of Panax 

 (family Araliaceae). These shrubs (P. Colensoi, P. arboreum, and P. simplex) 

 are often barked up to 3 ft. or 4 ft. from the ground, the white wood beneath 

 showing the imprint of large teeth. In the Marlborough Sounds goats are 



*_High up orTNgauruhoe rabbits are similarly exterminating L. aromaticvm. 



