Our IJviiif; Rcs<}i<ivt's — ReptiU's and Amphibians 



139 



The decline o\' the Santa Rita Mountains 

 population began in 1977 (Fig. 2). Total num- 

 bers of frogs (adults and juveniles) captured 

 plummeted from 252 in 1976 to 46 in 1977: 

 estimated total population size fell from a max- 

 imum 1,020 frogs to 625 (Hale and May 1983). 

 In June 1977 some captiued frogs became unre- 

 sponsive and often died, apparently I'rom the 

 stress of capture, a response not previously 

 observed. In 1978 no frogs marked in prior 

 years, nor tiny larvae attributable to that year's 

 breeding, were found. Larger tadpoles from 

 1976-77 persisted. Twenty newly metamor- 

 phosed frogs were observed in 1978 and 40 in 

 1979: from 1980 to 1982 we saw one to three 

 frogs attributable to those frogs. In spring 1983 

 the last known Tarahmnara frog in the United 

 States was found dead. Repeated visits (some 

 times yearly) to all former Arizona localities 

 have yielded no additional sightings. 



Three of seven populations studied from 

 1981 to 1986 in northern Sonora appeared 

 healthy, with adult and juvenile frogs as well as 

 both small and large larvae, suggesting a stable, 

 reproductive population. Frogs were not seen at 

 three other sites where they had been found in 

 the 1970's and early 1980"s. The last popula- 

 tion, in Carabinas Canyon. Sierra El Tigre, 

 which contained numerous frogs and tadpoles, 

 was in the initial stages of a major decline when 

 first observed in fall 1981. Within a year all 

 frogs had disappeared from the downstream end 

 of this population, but frogs in the upper portion 

 of the drainage appeared to have suffered no 

 decline in numbers through our most recent 

 visit to the site in 1986. 



Carabinas Canyon frogs displayed clinical 

 signs suggestive of heavy metal poisoning, 

 including inegular muscular acti\ ity and failure 

 of muscular coordination (ata.xia). partial paral- 

 ysis of the hind legs, dilated pupils unrespon- 

 sive to light, and a loss of the righting response. 

 The skin was often dry on the head and back. 

 Symptoms were amplified by the stress of cap- 

 ture and handling. Frogs displaying obvious 

 signs of heavy metal poisoning were already 

 dying. 



Field examinations of dead frogs showed no 

 evidence of gross pathological disorders. Skin 

 cultures showed no common pathogens; species 

 representing probable normal skin flora and 

 opportunistic secondary pathogens attacking a 

 debilitated host were present. Histopathological 

 examinations of five dying frogs (E. Jacobson. 

 J. Hillis Miller Health Center. College of 

 Veterinary Medicine, Gainesville, Florida) 

 revealed no gross pathologies (Hale and May 

 1983: Hale and Jarchow 1988). 



Populations of Chiricahua and Yavapai leop- 

 ard frogs (Rana chiricahuensis and R. yava- 

 paiensis) declined with the Tarahumara frog 



Arizona 



' Tucson 



New Mexico 



M Smelters 



A Local extinction 



y^ Declining but present 



ik Historical location 



where they occurred together, although leopard 

 frogs were not eliminated from most 

 Tarahumara fixig sites. In Sycamore Canyon. 

 Chiricahua leopard frogs have managed to 

 maintain a small but viable population near 

 Yank Spring, but numbers decrease downstream 

 in previously favorable leopard frog habitat. 

 The Chiricahua leopard frog has experienced 

 catastrophic declines elsewhere, and is in dan- 

 ger of disappearing from most of its range 

 (Clarkson and Rorabaugh 1989). 



Rain collected at the Sonoita Creek and 

 Canelo Hills preserves in the summers of 1982 



250- 



Fig. 1. Range of the Tarahumara 

 frog. Rana tarahumarae. Copper 

 smelters are at Douglas, AZ (now 

 closed), and Cananea and 

 Nacozari, Sonora. Historical loca- 

 tions include both surveyed popu- 

 lations thai appeared stable, and 

 unvisited historical localities 

 (Campbell 19.^1; Little 1940; 

 Williams 146(1; Hale et al. 1477; 

 Hale and May 198.^; Hale and 

 Jarchow 1988). 



200 



150 



100- 



50- 



Juvenlles 

 Adults 



I 



75 77 79 81 83 85 87 

 Year 



91 93 



Fig. 2. Number of Tarahumara 

 frogs captured 1975-93. Big Casa 

 Blanca Canyon. Santa Rita 

 Mountains. Santa Cruz County, 

 AZ (Hale and May 1983). 



