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Arkansas Tarantula Survey
Tarantulas in Arkansas: Why are they here?
Tarantula (Ronald F. Billings)
Only one tarantula species is thought to occur in Arkansas, Aphonopelma hentzi, commonly referred to as the Texas brown tarantula. Due to the many problems with tarantula taxonomy, the possibility exists that more than one species could occur in the state. The presence of tarantulas in Arkansas harkens back to a time, about 4,000-8,000 years ago, when the climate in this part of North America was much warmer and drier. As a result of higher temperatures and lower amounts of rainfall, open, dry habitats more typical of the American southwest and Great Plains expanded further eastward. As these habitat types expanded into Arkansas, animals and plants adapted to arid conditions expanded their ranges further east as well. Along with tarantulas, other arid-adapted species that made their way into Arkansas during this time include the striped bark scorpion, giant red-headed centipede, collared lizard, prickly pear cactus, and yucca.
Sandstone Glade (John Pelton)
However, as the climate cooled and rainfall increased, these species did not retreat back to the southwest and Great Plains. Instead, they became isolated within suitable patches of dry, open habitat surrounded by increasing amounts of forest. Many of these arid-adapted species can now be found in a type of habitat called a glade. Glades are very dry, open areas characterized by thin soils and exposed bedrock. The vegetation of glades typically consists of grasses and other herbaceous plants that tolerate dry conditions. The thin, poor soils, along with fires that would burn through glades, historically limited the presence of trees in these areas. Arkansas possesses a number of different types of glades, all differentiated from one another based upon the type of rock (sandstone, limestone, dolomite, shale) that underlies the area.
Today, glade habitats are no longer as common as they once were. The glades of Arkansas have been subjected to mining, overgrazing, and have been destroyed outright through development. Fire suppression has also lead to the degradation of large areas of glade habitat. Without fire, glades can be invaded by some woody plants, most notably eastern redcedar. As eastern redcedar moves in, the area of useable habitat for glade-associated species is reduced, or in some cases even eliminated. Loss of glade habitat has probably played an important role in the decline of some species, some of which are now considered threatened or endangered, including the federally threatened Missouri bladderpod (found only in Arkansas and Missouri).
