PROTECTIVE MIMICRY. 235 



Mimicry among Mammals. 



It is a remarkable fact that so extremely few cases of 

 mimicry among the Mammalia have been placed on record ; 

 I cannot help thinking also that it is a highly significant fact. 

 There can be no a priori reason against the occurrence of 

 mimicry in this group ; on the contrary, many considerations 

 seem to point to the great advantages which would be secured,. 

 by a defenceless quadruped mimicking one that, for some 

 reason or other, was little attacked by predatory enemies. The 

 chief foes of the herbivorous Mammalia are, perhaps, the 

 carnivorous members of their own order ; but a good many 

 of the smaller species rodents and iusectivores are devoured 

 by predaceous birds, not only hawks and eagles, but also 

 by the raven and other birds of the crow kind ; many 

 mammals in tropical countries fall victims to alligators and 

 crocodiles. 



Now, all these foes of the unprotected Mammalia are ad- 

 mittedly creatures which have a keen sight. Many of the 

 Camivora, notably the Cats using the term, of course, in a 

 wide sense, to include lions, tigers, panthers, and so forth 

 appear to hunt their prey almost entirely by sight. Dr. Hill* 

 has come to the conclusion that " in the dog the sense of smell 

 is paramount, in the cat it is largely replaced by hearing and 

 sight, in the otter it is extremely deficient." This conclusion, 

 based upon the varying development of certain parts of the 

 brain connected with those three senses, appears to be borne 

 out by actual observations upon the habits of the animals. 



As to birds, it is generally agreed that the sense of sight is 



far more perfectly developed than that of smell. In fact, if it 



were not so, the theories of warning colours and mimicry 



would at once fall to the ground, since it is especially birds 



* " The Plan of the Central Nervous System." Cambridge, 1885. 



