The six senses 六根 are likened to six wild creatures in confinement always struggling to escape. Only when they are domesticated will they be happy. So is it with the six senses and the taming power of Buddha truth. The six creatures are a dog, a bird, a snake, a hyena, a crocodile (śiśumāra), and a monkey.

A Dictionary of Chinese Buddhist Terms, William Edward Soothill and Lewis Hodous