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.
Many of these ships were never found, so the exact number of shipwrecks in the Lakes is unknown; the Great Lakes Shipwreck Museum approximates 6,000 ships and 30,000 lives lost, while historian and mariner Mark Thompson has estimated that the total number of wrecks is likely more than 25,000.