Fennec foxes and jerboas have fur on the bottoms of their feet. The furry bottoms stop their paws from getting burned on the hot sand.
The bottoms of fennec foxes' and jerboas' feet are covered in fur. This fur protects their paws from the heat of the sand.
Fennec foxes and jerboas grow fur under their paws to keep them safe. That fur keeps the hot sand from hurting their feet.