Adults don t give alarm calls for baboons even though their offspring are particularly vulnerable to baboons. However, the communication system is adaptive for survival. Cheney and Seyforth wanted to know how primate communication systems reflected human communication systems from a mechanistic point of view. Bernd Heinrich took a more adaptationist approach to studies of ravens in the Maine woods. Ravens feed on dead carcasses in winter.
Carcasses are hard to find, hard to break into because the surface can freeze.
Ravens aren t common either. Heinrich saw 15 ravens eating a dead moose. Thought that ravens had yelled to attract other ravens. Birds are one big family. Birds should be related.