Estivation is another form of torpor, dormancy, or "sleep".  Animals that estivate are trying to escape things happening in their environment.  This happens in hot, desert climates where heat and water are so important to the animals that live there.  Estivation protects these animals from high temperatures and drought.
    Just as animals hibernate in order to stay alive in cold places, animals estivate [or aestivate] in hot, dry places.  The bodies of estivators will slow down.  Breathing and heartbeat get very slow.  The animal doesn't need as much food and water to live since food is fuel for energy and they aren't using much.  Reptiles use 90-95% less energy when they are estivating.  Animals don't move, grow or eat during this time.
    When hot and dry times come, estivators will find themselves a safe place to sleep--usually underground.  This is the only way some animals can live through high heat and no water.
     Some examples of estivators are: