Sometimes for unknown reasons (whether because of the cold, whether because of non-compliance with hygiene) several animals tails firmly glued together. Formed "the rat king" - the many-headed, multilegged creature. I think if it happens only black rats. The king get his food cannot and goes to the full Board of his subjects. And subjects voluntarily feed him.
The king until the end of days tied to the place. Rats with normal tails are not averse to walk. Ten years ago in new York was all this time the rat mob under the leadership of Charlie - so the police have dubbed her mother well the rat. In 1966, hundreds of thousands of rats in Thailand, too, felt a desire to change places. They roamed through the country, crossed rivers. (Rats don't like to swim, but if need be will catch fish.) And yet the most breathtaking travel rats owe people - ships and trains have transported them across the planet.