The Japanese giant salamander, being restricted to streams with clear cool water, is entirely aquatic and nocturnal. Unlike other salamanders who lose their gills early in their life cycle, they only breach their heads above the surface to obtain air without venturing out of the water and onto land. Also due to their large size and lack of gills, they are confined to flowing water where oxygen is abundant. When threatened, these salamanders can excrete a strong-smelling milky substance whose odor resembles that of Japanese pepper (hence its name, giant pepper fish). It has very poor eyesight, and possesses special sensory cells covering its skin, running from head to toe and termed the lateral line system. These sensory cells host hair-like shapes that detect minute vibrations in the environment, and are quite similar to the hair cells of the human inner ear. This feature is essential for its hunting because of its poor eyesight. It feeds mainly on insects, frogs and fish. It has a very slow metabolism and lacks natural competitors. It is a long-lived species, with the captive record being an individual that lived in the Natura Artis Magistra, the Netherlands, for 52 years. In the wild they may live for nearly 80 years.