34 



ANIMAL DEFENCES 



under similar circumstances, and this possibly prevents other 

 animals from assaulting them. 



Many poisonous serpents are accredited with producing terri- 

 fying or warning sounds, which may or may not be associated 

 with the other warning methods above described. The character- 

 istic hissing is probably a 

 case in point, and very pro- 

 bably the rattle of the pro- 

 tectively - coloured Rattle- 

 snake may answer the same 

 purpose (fig. 485). 



It is well known that the 

 skin of Amphibians is pro- 

 vided with numerous small 



Fie. 485. Rattle of Rattlesnake, a, In section; b, exterior - - r 1 . i i 



glands of which the secre- 

 tion is more or less poisonous, and the common Toad, for example,, 

 is on this account treated with a fair amount of respect by Dogs,, 

 Cats, and the like. 



There are certain species of Amphibia where these poisonous, 

 properties are advertised by the presence of warning colours. The 

 conspicuous black -and -orange hues of the Spotted Salamander 

 (Salamandra maculosa) may be of this nature, though a clearer 

 case is afforded by a small red-and-blue frog described by Belt 

 (in A Naturalist in Nicaragua). The observer mentioned, sus- 

 pecting from its bold demeanour and glaring colours that this 

 species was inedible, found by experiment that it was invariably 

 rejected by fowls and ducks. A still more interesting case has 

 recently been described by Annandale (in The Proceedings of the 

 Zoological Society of London, 1900) of an Amphibian which only 

 shows bright colours when alarmed. This is a species of Toad 

 (Callula pulchrd] "which is found not uncommonly in the Siamese 

 States, among the rubbish which collects under the houses and 

 in like situations. In this species, the upper surface of which is 

 otherwise of a warm brown colour, a broad yellowish stripe runs 

 along either side of the back; but the peculiar looseness of the 

 skin and the folds into which it naturally falls prevent this stripe 

 from becoming conspicuous. When the animal is disturbed, how- 

 ever, it draws air into its lungs until its body becomes almost 

 globular, and the skin is stretched in such a way that its con- 

 trasting colours are displayed to their best advantage." This and 



