72 The Study of Animal Life PART i 



heights. A young one about six months old being left 

 behind called loudly for aid. " One of the largest males, 

 a true hero, came down again from the mountain, slowly 

 went to the young one, coaxed him, and triumphantly led 

 him away the dogs being too much astonished to make an 

 attack." 



FIG. 15. Chimpanzee (Anthropopithecus or Troglodytes calvus). 

 (From Du Chaillu.) 



Many birds, such as rooks and swallows, nest together, 

 and the sociality is often advantageous. Kropotkine cites 

 from Dr. Coues an observation in regard to some little cliff- 

 swallows which nested in a colony quite near the home of a 

 prairie-falcon. " The little peaceful birds had no fear of 

 their rapacious neighbour ; they did not let it even approach 

 to their colony. They immediately surrounded it and 



