Mammals are common, but since most animals are secretive, visitors usually see white-tail deer, cottontail rabbits, jackrabbits, and perhaps an occasional skunk or porcupine.
Like the flora, Amistad’s fauna also represents an area of transition. Many tropical species, especially birds, are at or near their northern limits. Great kiskadees (a flycatcher), olive sparrows, and two tropical kingfishers, the ringed and green, can be seen in the Amistad area. Tropical butterflies, like the white peacock, ruddy daggerwing, common mestra, and the polydamas swallowtail may be found.
Perhaps Amistad NRA’s greatest wildlife phenomenon is the fall migration of Monarch butterflies. Around October, just after the first major autumn cold front, thousands of Monarchs pass through this part of Texas on the way to their wintering grounds in the mountains of central Mexico. They roost in trees in the hundreds, waiting for favorable winds from the north to help them on their journey south.