Animal in the dessert that has big ears which give off heat to cool off and it hops very fast?

The animal you're describing is likely the fennec fox. Native to the Sahara Desert, the fennec fox has large ears that help dissipate heat, allowing it to regulate its body temperature in the extreme desert climate. Additionally, it is known for its agility and speed, enabling it to hop quickly across the sandy terrain to escape predators and catch prey.