Armadillo Decline
The armadillo family shows all the signs of being
in decline. Its range is restricted to tropical and subtropical America. The living
species are few and specialized in habit, being limited to running and digging. There are
no climbers or swimmers. The largest living species, the giant armadillo, is dwarfed by
the fossil
glyptodon that stood 5 feet high. If
no more, this suggests a dying down in the adaptability in the race as a whole. The fairy
armadillo, perhaps the most specialized, is also the most restricted. Its final stronghold
in the sandy plains of Argentina is now being threatened by expanding agriculture.
Although the armadillos seem to be declining, and
everything points to this, one species is actively extending its range. This is the
nine-banded armadillo. In 1880 it lived little farther north than the Lower Rio Grande
Valley on the borders of the 
United States and Mexico.
By 1905 it had moved into the western half of Texas as far as the Colorado River. Since
then it has moved across to Kansas and Missouri. Its has occasionally been found in New
Mexico and Oklahoma but has not become firmly established. It has been introduced to
Florida.
Why this sudden burst of life should have occured is not known. There is little sign that the nine-banded armadillo is enjoying especial freedom from enemies, abundance of food or a rapid rate of breeding. Rather the reverse is true. Usually a zoological group, like an individual, reaches a peak of development, then declines. There are, however, one or two examples from the fossil record suggesting that groups may take on a new lease of life.
