Thomas of Cantimpré [circa 1200-1272 CE] (Liber de natura rerum, Quadrupeds 4.66): The otter [luther], as he says [i.e. Liber rerum] is a cunning and mischievous animal living around ponds and rivers. It is about the size of a walleye [fish], and the shape is almost similar. It is brown and black in color, with shiny skin. This animal has dens above the waters and ponds, in which it lives and breeds. It lives on fish and hunts them with amazing frequency. Although it may live long under the waters, yet it draws its breath from the air, whence it sometimes happens that, where there is a gurgus, an instrument made of sticks for catching fish [i.e. a fish trap], it enters in the search of prey, but because it does not want to abandon the prey and cannot return by the place by which it entered, because the nature of the trap prevents escape, and the trap itself being not quickly torn, it must be suffocated in the meantime in the water, because it could not recover its breath in the air. This beast is so greedy for food, that it collects the fish it catches in its den, in which it hides, in such a heap, that from the excessive stench of decay produced from the putrid fish, it infects not only the cave, but also the air, which is not without its own danger, as any who want to capture this beast experiences. This beast is sometimes domesticated by fishermen and is sent into the water, which forces the fish to enter the dangers of their nets and be caught by their gills. Hence it seems to be of great benefit to its owners. - [Badke translation/paraphrase]