Scientists believe that the unique eating habits of wood-eating catfish evolved from the long-term competition with other catfish in the rivers of the Amazon basin. Germain said, "In the Amazon basin where these catfish live, rocks are rare. There is more mud, water and wood. Therefore, wood is a food source for fish. " In the Amazon basin, there are about 700 species of catfish living in * * *, and they make a living by scraping organic materials on the surface of objects such as wood. By swallowing wood, wood-eating catfish can make use of organic matter, microorganisms and microbial by-products in the space between wood fibers. Germain believes that "this digging ability has become an advantage because it can help catfish get food that other surface predators can't get."