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INVASIVE SPECIES OF OUR REGION Main sources: Tellman, Barbara, ed., 2002, Invasive Exotic Species in the Sonoran Region, Tucson: University of Arizona Press and the Arizona-Sonora Desert Museum; Collins, James, "Where have all the Frogs Gone?", Natural History June 2004, pp. 44-49; Note: this page is under construction. Comments and suggestions are welcome. ANIMALS By "invasive species" we mean those exotic species (introduced -- usually by humans -- from outside the reference environment) which have become so well adapted to their new environment that they interfere with the species that are native there (here we follow the definition provided by Tellman et al, 2002, pp. xix-xx). As a general rule, the more disturbed a habitat is by human activity, the higher the number and percentage of non-native species will be. Other factors support the invasion of exotics. For example, in the Southwest, most native plants (cactuses, shrubs, and trees) have evolved so they do not form continuous stands, and so most of them do not support wildfires, and consequently such plants have not fire-adapted and are seriously damaged by fire. In contrast, many invasives cluster into continuous stands, support wildfires and thrive on them. The purpose of the present pages is to identify the invasives appearing on Saguaro Juniper lands so that we may identify relevant locations and be prepared to act if and when these forms appear to be threatening our natives or are otherwise damaging the ecosystem.. What follows below is structured mainly by the list provided by Tellman et al (op.cit.), of "the most invasive exotic species in the Sonoran Desert Region", supplemented by additional exotics specifically present in our area as we identify them. (Click on names printed in blue and underlined below for elaborations on the relevance of these life forms to our Saguaro Juniper area.) Insects: European Honeybee (Apis mellifera) Honeybees were introduced into Mexico by the Spaniards, who prized them for both honey and candle wax. Although some Native American peoples had long kept native bees for their wax and honey, by the 19th century the European honeybee became dominant, and the bees spread from there into the Southwest. (Honeybees also came here from both California and the eastern U.S. during the 19th century, and of course the Africanized honeybee -- a co-specific of the European race -- has arrived late in the last century.) Amphibians: Eastern Bullfrog (Rana catesbeiana) Bullfrogs are native east of the Mississippi River, but were introduced into Arizona in the 1920s by what is now the Arizona Game and Fish Department, which observed at the time that "These lusty chaps seem to prosper in our climate," and that the Department sought more opportunities for the public to "enjoy frog hunting as a sport and frog flesh as food...."(Tellman, p. 43). The practice of inserting thousands of tadpoles into Arizona streams continued into the 1980s. Bullfrogs are voracious predators (butterflies, dragonflies, native frogs, fish, turtles, birds and small mammals), and reproduce prolifically. According to Collins (cited above, pp. 47-48), these invaders are gradually becoming a global displacer of native amphibians, not only through competition and predation, but also by carrying new pathogens (fungi and viruses now known to be contributing to declines of native frogs).
Reptiles: Crustaceans: Crayfish (Orcontectes virilis & Procambaus clarkii) Crayfish are voracious eaters of snails, tadpoles, native fish (our local native fish appear to be especially vulnerable), frogs, and small turtles, and they disturb stream bottoms and thus increase the murkiness of water, inhibiting plant growth. In doing so, they strip streams of aquatic plants. We have not yet encountered them in the Hot Springs Canyon area. For more details and images of crayfish, see this link: http://www.usgs.gov/invasive_species/plw/crayfish.html Mammals: Feral domestic cats (Felis catus) Rats Fish: Mosquito fish Green sunfish other fish
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