Biomes are the ecosystems in which animals live and can be they separated into several categories. The animals living in those biomes adapt for maximum survival, both physically and behaviorally. They adapt by a wide range of mechanism and how they choose to adapt a certain way is not known, but adapt they do!
Deserts are an extreme land biome. With little moisture, limited plant life, and no water, you would expect the animal life to be similar or adapted in similar ways, but it isn't!
There is the Desert Spade-foot Toad the thrives when the rain falls, but then suddenly starts to dig holes, line them with mud, and then bury itself. As the mud dries out, the toad's body starts to shut down and undergoes estivation, a process similar to hibernation but as a result of heat rather than cold. The toad sits dormant until rain starts to fall. Other creatures in the same desert have evolves to survive off the water in seeds and cacti, their metabolism can actually increase as the environment dries out. They increase their range and start to look for more food and water sources. Both are adapting physically and biologically to their biome, but in different ways!
Budgies from the Australian desert only breeds when there is sufficient water and other birds around. This is because eggs require a lot of water to produce and the budgies are social animals, caring for each other's offspring. This ensures survival of the species, if not the individual. Birds in the same area drive off all others except their mates to be sure to keep the food for themselves. Both situations are physical and behavioral adaptations to the desert biome!
How the physical and behavioral adaptions got started and why they work the way they do is a source of spectulation. The truth can never be known, only guessed. Why does one bird form colonies while the other isolates itself? Scientists can give you advantages for each adaptation, but not the reason for one being better than the other, they both obviously work!
The adaptations over time have been what shaped the animals, many call it evolution. Bats rely on sound rather than sight, but owls have exception vision, but both, like all creatures, have adapted physically and behaviorally to their biomes, and living at night! Nature and the animals that live in it are amazing.