Animals are so prevalent in Momaday's writing because the Kiowa depended on animals for their livelihood and prosperity.
The Kiowa, being a semi-sedentary tribe, migrated with the American bison, their main food source along with turkey, deer, antelope and plants like wild berries and wild fruit.
Furthermore, they used dogs to drag travois that had camping goods, and when they acquired horses from Spanish rancherias, they became a fully mounted warrior nation.