THE COLOURS OF DESERT ANIMALS 157 



History Museum in Kensington, and shown the large 

 case which illustrates desert hf e. We remember the 

 sandy rocks, the sparse dry vegetation and the birds, 

 beasts and reptiles all coloured so that they were 

 inconspicuous. We did not reaHze that they were 

 inconspicuous, at any rate in part, because they 

 were motionless, and that about half the creatures 

 in the case were strictly nocturnal. We were told 

 that the animals were so coloured as a protection 

 from their enemies, and most of us have grown up 

 without ever critically examining this statement, so 

 that the theory of protective coloration is still widely 

 accepted by people who are not strictly scientists, 

 but are very deeply interested in biological problems ; 

 the time has come to examine it very closely. This 

 theory presumes that there are predaceous creatures 

 from which the animal must be protected, or else 

 that the animal is itself predaceous and that its 

 colour enables it to stalk its prey with success ; the 

 theory presumes also that the protection given is 

 actually effective under natural conditions in the 

 open desert. One asks at once from what enemies 

 the desert creature needs to be protected. Admit 

 that the moths, grasshoppers, mantids, spiders, 

 and other smaU organisms are preyed upon by 

 insectivorous birds and reptiles, and suppose that the 

 colour of these small animals gives them some 

 measure of safety ; the supposition is not based on 

 accurate knowledge, but it is not unreasonable. 

 Now, what are the enemies of the larger "pro- 

 tectively coloured " birds, the Sandgrouse (Pterocles) 

 and Courser (Cursorius) ? 



