Where are the rats running from the ship?

Almost 70 species of rats live in the world, but the man’s neighbor is only a gray rat. She settles everywhere where there is shelter, access to food and water, and the greater the room, the greater its population. Therefore, landfills, warehouses, livestock complexes, houses with garbage chute, trims of ships for her native house.

True, people animals face, activating by the night and again hiding in shelters for about 8 am when we go to work. At other times, rats can be seen only if something went wrong – for example, there is no longer enough food or need new refuge. Then they run.

And run quite well – at a speed of up to 9.6 km / h. For comparison, pedestrian speed – 5 km / h. Still rats are excellent swimmers and can swim up to 2 km. So imagine the rodent running from the ship simply: jump off, float and saved – such a logic sees such. But she is mistaken.

When the ships were still sailing, the sailors noticed that many rats would run out of some on the pier. Subsequently, these ships endured crash in a bora or because of the attack. So born belief that the future would foresee the future and saved in advance.

But! First, ships stood in harbors. No one watched rats jumping into the sea. Secondly, cases where the rats ran away, and the ship returned safely, was not discussed.

Here you need to remember another story. During World War II, the mathematician Abraham Wald received an extraordinary task: to decide which places on American aviation bombers need to be strengthened. Statistically, they were calculated, and everything seemed obvious, but Wald pointed out other places of the building – those with samples in which the planes would not be able to return. The principle was called the "systematic error of the survivor". Its essence is that when analyzing events, the conclusions are built only in cases.

So the trums of the ships of the rat left not because shipwrecks waited. Cause in the other. These rodents live families who have a lifetime. The ship is a place where they breed very quickly, thanks to the large space, the abundance of materials for the dwellings and food availability. The family grows, places soon ceases to grab, and the rats are forced to look for a new one, more than the former. And the fact that some ships after that tone, most likely nothing more than an accident.