136 ANIMAL LIFE IN DESERTS 



several birds, but by none more than by Hypocolius 

 ampelinus. These instances must not be supposed 

 to imply that fleshy fruits are common in deserts ; 

 the reverse is the case. 



Animals serve the plants by distributing their 

 seeds, but they do immense harm to the vegetation by 

 devouring plant and seed ahke. The deserts of the Old 

 World support large numbers of domestic goats, sheep, 

 cattle, and camels, and of wild gazelles, antelopes, 

 and hares, and these animals Hve by browsing shrubs 

 and herbs. In the neighbourhood of a bedawin 

 encampment or an Arab village or a frequented 

 track it is almost impossible to find an untouched 

 plant of any kind. Cannon observed in Algeria 

 that the Mzabite cemeteries, in which the domestic 

 animals are not allowed to graze, form a place of 

 refuge to plants which otherwise do not exist at all 

 near the haunts of man. It is frequently stated that 

 thorns (page 62) are produced as a defence against 

 these browsing animals, and this explanation may be 

 true in some places, but certainly does not fit the 

 facts very generally. In favour of the defensive 

 theory is the fact that in the Southern United States 

 and in parts of Australia, where species of Opuntia 

 (" Prickly Pear ") are used as food for sheep and 

 cattle, only the thorny species can be successfully 

 grown. If the thornless species are planted they 

 must be protected by fencing against the grazing 

 animals, and it is actually cheaper to grow the 

 thorny species and to destroy the thorns by fire, 

 when the plant is required for the stock, than to 

 protect the thornless ones with fences. It is a fact 



