322 ANIMAL DEFENCES 



has been rendered less useful because it has also been adopted 

 by certain natural enemies, i.e. Owls, which are among the most 

 persistent foes of small rodents. In these birds the nocturnal 

 habit has almost certainly been acquired for aggressive pur- 

 poses. It is interesting to note that some members of the order 

 possess the large eyes characteristic of thorough -going nocturnal 

 species. This is the case, e.g., with the Egyptian Jerboa {Dipus 

 yEgyptiacus). 



The Edentates, like many other ancient and primitive groups, 

 are markedly nocturnal, and the leaf-eating Sloths in particular 

 probably derive a good deal of protection from the habit. The 

 same remarks apply to the more defenceless vegetable -feeders 

 among the Marsupials, such as the Phalangers, Koalas, and 

 Wombats. The more powerful Kangaroos, on the other hand, 

 feed by day, while the rapacious Dasyures and the Tasmanian 

 Wolf prey at night on weaker animals. 



The feeble members of the lowest group of Mammals, the 

 Monotremes, are nocturnal in habit, the Spiny Ant-eaters entirely, 

 and the Duck-billed Platypus largely so. 



Birds are essentially a day-loving class, and when nocturnal 

 habits have been acquired, as in owls and night-jars, they chiefly 

 have reference to the nature of the prey. In some few cases, 

 however, the night-feeding practice would appear to have a pro- 

 tective meaning, as, e.g., in two New Zealand birds, the Owl-Parrot 

 or Kakapo {Strmgops habroptihts) and the Kiwi {Apteryx). The 

 former feeds chiefly on vegetable matter, and being practically 

 devoid of flying powers is singularly defenceless; its time of 

 activity might be divined by the owl-like character of its head. 

 The Kiwi is the smallest and most defenceless of the runnine birds. 



Among Reptiles, — Crocodiles and large Snakes, such as 

 Pythons, are respectively largely and entirely nocturnal, but pro- 

 tection is not the end to be attained. A case, however, of which 

 the meaning is probably partly protective, is afforded by most of 

 the species of the litde climbing lizards known as Geckos, of which 

 large eyes are characteristic, and these organs exhibit the vertical 

 pupils often found among nocturnal forms. The specialization 

 even here, however, has no doubt as much reference to the pursuit 

 of certain sorts of insects under favourable conditions as to protec- 

 tion ; indeed, the former may be the chief object of the habit. 



Although Amphibians constitute a group which is predomi- 



