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.
The shipbuilding industry turned out thousands of cargo ships for wartime service. The United States learned how to mass-produce merchant ships during World War I. Three decades later, convoys of American Liberty and Victory ships delivered tons of fuel, ammunition, and other supplies to fight World War II. At least 1,500 merchant ships were sunk during the war.