to investigate actions of water in keratin, the piezoelectric, dielectric, and elastic constants are measured at 10 hz, at temperatures between -160 and 150 degrees c, and at various hydration levels. from changes in the piezoelectric, dielectric, and dynamic mechanical parameters with moisture content (m.c.), the authors have identified three regimes (i, ii, and iii) in the hydration of water for keratin. at high hydration (21 percent m.c.) around o degrees c, the piezoelectric constants for keratin steeply decrease with increasing temperature. this may be attributed to interfacial polarization which is strongly related to self-associated water molecules (particularly regime iii water) just around crystalline helical regions which can exhibit the stress-induced, i.e. piezoelectric, polarization and may be attributed to electrode polarization induced by the increase of mobile ions in the amorphous matrix region, some of which would be released from their trapped states just around the piezoelectric phase by the regime iii water