What is the mystery of Daming Lake in Jinan?

There are two puzzles in Daming Lake, Jinan City, Shandong Province: First, is there a snake? According to the general law, wetlands are places where snakes inhabit and multiply. There are many snakes in other parts of Jinan, but there are no snakes in more than 80 hectares of Daming Lake Fiona Fang. Second, frogs don't bark. There are frogs in Daming Lake, but they don't bark. Once a busybody moved the frog in Daming Lake outside the moat, and the frog cried. Put frogs that can bark outside into Daming Lake, and you will never hear them again. In recent years, biologists have done serious research, from the water temperature and water quality of Daming Lake, to see whether the water temperature and water quality of Daming Lake have any influence or whether there is any difference in the physiology of frogs in the water, but the research has not yet reached a result.