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.
Lusitania. The Lusitania was a British passenger ship that was sunk by a German U-Boat on May 7, 1915. 128 Americans died. The unrestricted submarine warfare caused the U.S. to enter World War I against the Germans.