500 CHAINS OF CIRCUMSTANCE 



of the introduction of Rabbits is a tendency on the part of 

 heather moor to disappear and be replaced by grassy moor- 

 land. How this change from heather to grass must influence 

 the animals in the area affected the reader can guess. 



INFLUENCES OF SHEEP, GOATS AND RABBITS 



When Neolithic man drove his flocks before him across 

 the dry ground of the English Channel, he left them as far 

 as possible to roam at their own free will. Their numbers 

 were greater than those of the animals they displaced, so 

 that cropping of herbage became more intensive, and within 

 the forest and on its margin seedling trees were devoured 

 for their succulent leaves. As under the influence of Rabbits, 

 the general covering of the ground was affected. For many 

 years, on a portion of Scotstown Moor in the neighbourhood 

 of Aberdeen, Professor J. W. H. Trail has told me, Sheep 

 have been annually penned for short periods of ten days or 

 a fortnight, on their autumn migrations from the highlands 

 to the lowland feeding-grounds. There even so short en- 

 campments have caused noticeable changes in vegetation, 

 for the areas of the pens stand clear cut to-day in the midst 

 of the moor as areas in which heather has been banished and 

 has been replaced by "grass-heath" associations of plants. 

 Other results, to which I have already alluded (p. 323), 

 followed when the higher lands were cleared of their wild 

 fauna and the custom developed of sending Sheep and 

 Goats to pasture on the upland moors and hills. Here, as 

 food became scarce in winter time, they fed upon the seed- 

 lings which formed the advanced posts of the forest and 

 paved the way for new extensions of forest growth. The 

 extension of woodland in all areas open to the inroads of 

 flocks has been prevented. 



Further, even within the woodland, Sheep, Goats and 

 Rabbits are exceedingly destructive; young seedlings and 

 even sturdy trees up to three or four feet high are ruined 

 by the demolition of their foliage and leading shoots and 

 by the gnawing of their bark. So that when nature claims 

 an aged and timeworn member of the forest, there is no 

 fresh growth spontaneously to take its place; and the wood- 

 land, which was prevented from extending by these aliens, 



