The sensations caused by dehydration, the continuing loss of fluid through the skin and lungs and in the urine and feces while there is no water intake into the body. Thirst becomes more and more insistent as dehydration worsens. Water and electrolytes are needed to replace losses, and an adequate intake of sodium as well as water is important for maintaining blood volume. Herbivores and human vegetarians, whose diets lack sodium, have a natural appetite for sodium; however, severe sodium deficiency in carnivorous animals and humans can result in the development of a well-marked sodium appetite as well. Water intake varies considerably between individuals and depends on climate, custom, and diet. Reproduction affects drinking behavior; fluid intake increases during pregnancy and especially during lactation. Normally, the amounts of water drunk and taken in food are more than enough to maintain hydration of the body, and the usual mixed diet provides all the electrolytes required.