Western black-headed snake (Tantilla planiceps), also known as the California black-headed snake, is a snake species endemic to the Californias (the U.S. State of California and the Baja California Peninsula in Mexico), as north as the San Francisco Bay and as far east as western Utah. It lives in mostly moist pockets in mostly arid or semiarid environments, and spends much of its life underground. It has a flattened head as most crevice-dwellers, and is seven to fifteen inches in size. It is brown, slender, olive-gray, with a black head bordered by a white collar. Its habitat is often in woodland, desert areas, grassland and along arroyos in areas that are wet in a usually dry region.