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 odds on surviving a u-boat sinking were pretty long. 20 u-boats were sunk (counting 1 missing). Four u-boats had survivors, sixteen were lost with all hands. There were a total of 81 survivors and 953 killed of the u-boat crews.