The Biology of the Crocodilia 41 
mouths wide open it is quite possible that these 
birds may pick off the worms that are often found 
within. It is also possible that the alertness of 
these birds to danger may serve as a warning to 
the crocodiles with which they associate. 
According to Voeltzkow these crocodiles dig 
caves of thirty-nine to forty feet length in the 
banks of the streams they inhabit, into which they 
retire on the approach of danger. The caves open 
under water and slope upward towards the surface 
of the ground where a few small air-holes are 
found. The natives locate the caves by means of 
the air-holes and dig out the hidden animal, first 
stopping up the entrance. 
In Madagascar the eggs are laid in August and 
September and hatch in about twelve weeks; 
they are laid at night, usually shortly before day- 
break. From twenty to thirty eggs are laid in 
one nest, which is merely a hole dug in the dry 
sand. As was said in connection with the Florida 
alligator, the habits of the two animals are quite 
different in this respect,—the moisture that is so 
important in the one case is fatal to the embryo 
in the other. When the eggs are laid the nest is 
filled in with sand so that there is nothing to indi- 
cate its position except that the female crocodile 
is in the habit of lying on the spot where her eggs 
lie buried. 
Like the alligator the young crocodile makes a 
squeaking noise shortly before hatching and the 
