Flexi Says: Estivation is a dormant state that some animals enter into to survive very hot or dry conditions. Estivation is similar to hibernation, except that hibernation occurs during cold, winter conditions. For example, lungfish are freshwater fish, and during dry periods, they burrow into the mud and obtain all of their oxygen from air by using this primitive swim bladder-lung. When this happens, they enter estivation where they severely reduce their metabolic rate, so they are able to survive in this condition for several years. It is often a seasonal adaptation, and they emerge when water levels return.