FOOD AND GROWTH 61 



Although no reptiles live in organised communities after 

 the fashion of hamsters among rodent mammals and bees and 

 ants among insects, there are a few instances of certain species 

 living in companionship with other animals. In North 

 America, for example, rattle-snakes frequently take up their re- 

 sidence in the burrows of the " prairie-dogs," or prairie-marmots 

 (Cynomys), which are often also tenanted by the curious little 

 owls of the genus Speotito. It used to be supposed that these 

 strangely associated animals constituted a veritable " happy 

 family," but it is now ascertained that the snakes resort to the 

 marmot-warrens for the sake of feeding on the young marmots. 

 When there are no young ones, it would, however, seem that 

 the snakes live in a state of harmony — or at all events of " armed 

 neutrality" — with the marmots. 



Another instance of a similar kind of association is afforded 

 by the New Zealand tuatera (Spkenodon), whose burrows are 

 sociably shared by petrels of various kinds. The petrel is 

 stated to usually occupy the left, and the tuatera the right side 

 of the inner chamber of the burrow, which, by the way, is inva- 

 riably excavated by the reptile. The late Sir J. von Haast 

 observes that while very tolerant of the bird and its young, the 

 tuatera does not allow another reptile of its own kind to live in 

 the same hole, which it is ready to defend by lying in 

 such a manner that the head is placed where the passage 

 widens out to form the chamber. 



Another curious association between a bird and reptile 

 occurs in Egypt. Herodotus tells the story that a bird he 

 called Trocliilus enters the open mouth of a basking crocodile 

 to pick the fragments of food left between the teeth of the 

 reptile. For a long time this story was rejected as a " traveller's 

 tale," but modern observations appear to show that it is per- 

 fectly true. At one time the bird in question was supposed to 

 be the black-backed courser {Pluvialis (Bgyptiacus), but it really 

 appears to be the spur-winged lap-wing, or ziczac {Hoplopterus 

 armatus). An observer writing in 1870 stated that he saw a 

 bird which he believed to belong to the latter species deliber- 

 ately enter the mouth of a basking crocodile two or three 

 times ; and that during one of these visits the reptile actually 

 closed its mouth, opening it again after a time to let the bird out. 



