140 



Reptiles and Amphibians — Our Living Resources 



Tarahumara frog {Rana larahii- 

 inarae) in Mexico. 



For further information: 



S.F. Hale 



Herpetologist 



139 W.Suffolk Dr. 



Tucson, AZ 85704 



and 1983 was consistently very acidic, attrih- 

 uted primarily to particulates produced by a 

 copper smelter in Douglas, Arizona (Blanchard 

 and Stromberg 1987), which has since been 

 shut down. The alkaline soils in the area may 

 buffer the streams from the acid rain: stream pH 

 values were always slightly basic. 



Analyses of water from affected streams 

 showed consistently elevated levels of cadmi- 

 um, a toxic metal, especially in relation to lev- 

 els of the essential metal, zinc. In several 

 species of vertebrates, sensitivity to cadmium 

 toxicity is reduced with zinc supplementation 

 (Supplee 1963; Webb 1972). At Sycamore 

 Canyon and Big Casa Blanca Canyon localities, 

 frogs survived longest near springs where zinc 

 concentrations were highest. Levels of arsenic 

 in streamwater were occasionally elevated 

 (Hale and Jarchow 1988). 



Although the proximity of operating copper 

 smelters is correlated with population declines 

 in Tarahumara and leopard frogs, exact causes 

 of declines are not clear. No declines in frogs 

 were noted until the 1970's, yet copper smelter 

 emissions were much higher in the areas of 

 declines in the early 1900"s than recently. One 

 of our hypotheses that accounts for the timing 

 of the declines relates them to a long-term 

 leaching of acid-soluble zinc from canyon 

 walls, accumulation of insoluble cadmium in 

 stream sediment, and sediment accumulation in 

 stream pools from infrequent heavy rains before 

 declines. 



In southern and central Sonora, ranid frog 

 populations appeared stable and reproductive at 

 least through 1986: no population declines or 

 extirpations were noted, either of Tarahumara or 

 leopard frogs. Populations visited since 1986 do 

 not appear to be declining. 



Conclusions 



We are confident that the Tarahumara frog 

 no longer occurs in the United States, based 

 upon repeated surveys of historical and poten- 

 tial habitat in southern Arizona. Although 

 repeated surveys since 1983 in Mexico have not 

 been as extensive as in the United States, sites 

 visited in central and southern Sonora apparent- 

 ly continue to support healthy frog populations. 



We conclude that the Tarahumara fros is not 



threatened with extinction throughout its range 

 at this time, although the sudden declines and 

 local extiipations in northern populations, coin- 

 cident with declines of leopard frogs, are a seri- 

 ous concern. 



State and federal resource management 

 agencies in both Arizona and Sonora, Mexico, 

 with independent biologists and the Arizona- 

 Sonora Desert Museum (ASDM) and Centro 

 Ecologico de Sonora have formed the 

 Tarahumara Frog Reestablishment Oversight 

 Group. This group proposes to reestablish the 

 Tarahumara frog in selected historical sites and 

 maintain captive frog populations at ASDM and 

 elsewhere to provide stock for additional rein- 

 troduction. By intensively monitoring reintro- 

 duced populations and measuring important 

 environmental variables we hope to detemiine 

 the cause of declines in native ranid frogs in this 

 area. Rain, streamwater, and air quality will be 

 assessed continuously at each site, including 

 pH, heavy metals, solar radiation (especially 

 ultraviolet), and air particulates. Stream bottom 

 substrate and tissue samples from frogs and frog 

 prey and predator species will be sampled for 

 heavy metals. Only after the causes of the 

 declines have been identified and corrected can 

 we expect long-term reestablishment of 

 Tarahumara frogs and recovery of leopard 

 frogs. 



References 



Blanchard, C.L.. and M. Stromberg. 1987. Acidic precipita- 

 tion in southeastern Arizona: sulfate, nitrate and trace- 

 metal deposition. Atmospheric Environment 21:2.375- 

 2381. 



Campbell. B. 1931. Rana larahumarae. a frog new to the 

 United States. Copeia 1931:164. 



Clarkson. R.W.. and J.C. Rorabaugh. 1989. Status of leop- 

 ard frogs {Rana pipiens complex: Ranidael in Arizona 

 and southeastern California. Southwestern Naturalist 

 34:531-538. 



Hale, S.F.. and J.L. Jarchow. 1988. The status of the 

 Tarahumara frog iRana tarahumarae) in the United 

 States and Mexico: Part 2. C.R. Schwalbe and T.B. 

 Johnson, eds. Report to Arizona Game and Fish 

 Department. Phoenix, and Office of Endangered Species. 

 U.S. Fish and Wildlife Service. Albuquerque. NM. 101 

 pp. 



Hale, S.F. and C.J. May. 1983. Status report for Rami 

 tarahumarae Boulenger. Arizona Natural Heritage 

 Program, Tucson. Report to Office of Endangered 

 Species. U.S. Fish and Wildlife Service. Albuquerque. 

 NM. 99 pp. 



Hale. S.E. E Retes. andT.R. Van Devender. 1977. New pop- 

 ulations of Rana tarahumarae (Tarahumara frog) in 

 Arizona. Journal of the Arizona Academy of Science 

 11:134-135. 



Little. E.L.. Jr. 1940. Amphibians and reptiles of the 

 Roosevelt Reservoir area. Arizona. Copeia 1940:260- 

 265. 



Supplee. W.C. 1963. Antagonistic relationship between 

 dietary cadmium and zinc. Science 139:119-120. 



Webb. M. 1972. Protection by zinc against cadmium toxic- 

 ity. Biochemical Pharmacology 21:2767-2771. 



Williams. K.L. 1960. Taxonomic notes on Arizona herpeto- 

 zoa. Southwestern Naturalist 5:25-36. 



