From the Daily Collegian:

Stockholm, Sweden – In an embarrassing admission, Defense Ministry analysts say many signals detected by their navys high-tech buoys – and thought to be foreign submarines – were just the sounds of swimming minks.

The report – coming after the military conceded that an animal set off a weeks-long sub hunt in the Baltic Sea last spring – was leaked to the Dagens Nyheter newspaper and published yesterday.

It said most of the suspicious sounds heard in the islands around Stockholm since the end of the Cold War were minks and other mammals swishing and splashing as they searched for food. Minks, about the size of cats, are plentiful on the islands. They usually feed on the surface, but sometimes dive for crayfish on the bottom.