Answer:
lack of water and high concentration of heat and dryness
Step-by-step explanation:
Deserts don't get that much rainfall, so desert wildlife are adapted to survive in such a dry climate. Take the camel, for instance, it can store three bathtubs of water in it's hump, so it can go a very long time without water. And without that rainfall, the desert is dry and, usually, very hot. Animals have adapted to this by only coming out in the nighttime when it's cooler.
hope this helped:)