Why fewer animals live in desert than a rainforest?

Answer 1

There are two main types of desert: hot desert and cold desert (also called tundra).

In the tundra, animals need to be able to stay warm, and therefor there are few or no cold blooded vertebrates. Trees can't even grow in cold deserts because the winter is so cold that the soil stays frozen year round, just a few inches beneath the surface.

In hot deserts, plants are primarily affected by the heat because it increases the rate that water evaporates. However, desert plants are very good at conserving their water. For animals, hot deserts are often so hot, that they simply hide underground until nighttime. For those that don't, it increases how much water loss they have and thus, they need more water (although there are animals, like Meerkats, that live in hot deserts and still are active during the day, yet they get all of the water that they need from food).

Clarification:

Tundra and desert are two distinct biomes. While they may share some characteristics, they are different biomes.

Deserts are divided into two general types:

Hot Deserts - such as the Sahara, Arabian Desert, Mojave Desert

Cold Deserts - such as the Atacama, Gobi, Antarctica and Great Basin

Some cold deserts may get quite hot during the summer but winter temperatures can be very cold. They are sometimes called 'cold winter deserts.' Hot deserts usually stay mild in the winter but summers are very hot. Some cold deserts are classified as such because of their geographic location near the sea that tends to moderate their temperatures. Both the Atacama and the Namib Deserts are generally mild the year round with no temperature extremes. Sometimes they are labeled as 'cool coastal deserts.'

Answer 2

the reason why the animals live in the hot desert is because the majority of the animals are lizards and therefor they are cold blooded so they need heat in order to survive

Answer 3

Because there is less food, higher temperatures and fewer resting places than in the rainforest.