Instinctive behavior occurs when an animal has a particular internal state while it is in the presence of a specific external stimulation called a releaser or a sign stimulus.
How many ships did the U-boats sink? During the war the U-boats sank about 2,779 ships for a total of 14.1 million tons GRT. This figure is roughly 70% of all allied shipping losses in all theatres of the war and to all hostile action. The most successful year was 1942 when over 6 million tons of shipping were sunk in the Atlantic.
In terms of crew deaths, it lists them as follows (boat losses do not include scuttled boats in this breakdown): 1939 : 9 boats sunk and 204 sailors killed (148 survivors) 1940 : 24 boats sunk and 643 sailors killed (331 survivors) 1941 : 34 boats sunk and 887 sailors killed (645 survivors)