Fire creatures are about transmutation and change, dynamic growth, courage and strength of will. Ground-dwelling animals such as Moles or Prarie Dogs are Earth. Most creatures which don't fit the other elements, such as Deer or Wolf or Mouse, are also Earth. Don't be absolutist with these definitions, however. They are meant as a tool to learn from, not as a box to compartmentalize.
Many animals correspond to more than one element.
Butterflies may be Fire, but they also have Air qualities. Bear, who hibernates and dreams, also has a Water element. Some traditions correspond the Cat family to Fire. Hippo's Water and Earth create Mud. What does this teach you about the creature.