Tarahumara Frog (Rana tarahumarae)

Photo by Steve Hale

Photo by Steve Hale

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Description

Editor’s Note.  On 20 October 2014 a team of biologists led by the Arizona Game and Fish Department released 285 large juvenile Tarahumara Frogs and 297 Tarahumara Frog tadpoles into Sycamore Canyon west of Nogales, ending a 40 year hiatus during which the species was absent from that canyon. We follow Amphibiaweb and Yuan et al. (2016: Systematic Biology, doi: 10.1093/sysbio/syw055) in our usage of Rana rather than Lithobates for Arizona’s ranid frogs.

The Tarahumara Frog was described in 1917 as Rana tarahumarae by George Albert Boulenger from specimens collected at Ioquiri (=Yoquivo) and Barranca del Cobre in the Sierra Tarahumara of southwestern Chihuahua, Mexico. That name remained unchanged until Frost et al. (2006) proposed the genus name Lithobates for this species and most other North American ranid frogs. The proposal was adopted by the Society for the Study of American Amphibians and Reptiles (Crother 2008, 2012), but remains controversial (e.g. Pauly et al. 2009). No subspecies of the Tarahumara Frog are recognized. Hillis and Wilcox (2005) placed the Tarahumara Frog into the Tarahumara group of New World ranids, which also includes L. johni, L. pueblae, L. psilonota, L. pustulosa, L. sierramadrensis, and L. zweifeli. All frogs of this group lack vocal sacs and slits, have reduced or no external tympana, and they tend to be highly aquatic and typically occupy montane streams and plunge pools. The group is largely restricted to the Sierras Madre Occidental, Madre Oriental, and del Sur of Mexico (Hillis and Wilcox 2005). The Tarahumara Frog is the only member of the group that is known to vocalize, and is the only one whose range extends into the United States.

Fig. 1: Adult Tarahumara Frog reared from a portion of an egg mass collected in the Sierra de la Madera, Sonora.

Fig. 1: Adult Tarahumara Frog reared from a portion of an egg mass collected in the Sierra de la Madera, Sonora.

In southeastern Arizona, the Tarahumara Frog is akin to the Jaguar of the amphibian world, in that it is a species of remote places, often rugged barrancas and sierras with poor access, whose range barely extends into the United States. Also like the Jaguar, this species has declined, particularly in the northern portions of its distribution.

Description and Similar Species

This is a moderate-sized (< 114 mm SVL) robust frog with a rounded snout. Dorsally it is dark brown, gray, or olive-gray with few or no well-defined spots (Fig. 1, 2, 5). Usually across the dorsal surface of the hinds limbs are dark bars, which may be somewhat diffuse, or broken into spots and dark blotches. These markings may be absent or indistinct in individuals that are dark overall. The front limbs and sides may exhibit dark spots or blotches as well, and less distinct dark markings may be found on the back. The dorsum is relatively rough and pustulose for a Southwestern ranid frog. The venter is white or cream, sometimes with a dark or gray wash on the chin, throat, and chest. Dorsolateral folds are absent or weak, tending to be more prominent in southern populations (S. Hale, pers. comm.). A fold of skin runs from the eye back and around the small tympanum. The usually indistinct and minutely pustulose tympanum is about one-half the diameter of the eye. The Tarahumara Frog lacks vocal sacs or slits. The tips of the digits are slightly expanded, more so on the hind feet, and the digits of the hind feet are webbed to the tips.  Webbing is absent on the front feet. The eyes are large and the pupils are round. The iris is a gold-brown and flecked with black. Males are not as large (< 96 mm SVL) as the females and in adult males the thumbs are swollen and black. Tadpoles grow as large as 106 mm total length prior to metamorphosis. Larger tadpoles are brown, brownish-olive, or tan with numerous dark spots and blotches (Fig. 3). The spots may coalesce to form mottling on the tail. This description was compiled from the following sources: Zweifel (1968), Wright and Wright (1949), Hale and May (1983), and personal observations.

Fig. 2: Juvenile Tarahumara Frog from the Sierra de la Madera stock showing dorsolateral folds (typically weak or absent in this species).

Fig. 2: Juvenile Tarahumara Frog from the Sierra de la Madera stock showing dorsolateral folds (typically weak or absent in this species).

The only frog in the 100-Mile Circle with which the Tarahumara Frog might be confused is the American Bullfrog. It grows to a much larger size (< 203 mm SVL), has smoother skin, a distinct tympanum that is 1-2 times as large as the eye, and mottling on the chin. Leopard frogs have distinct spots on the dorsum and prominent dorsolateral folds.

Distribution and Habitat Use

The Tarahumara Frog is known from about 70 localities in the Sierra Madre Occidental and adjoining sky island mountain ranges west of the continental divide at elevations of 460-1860 m from south-central Arizona south through eastern Sonora and southwestern Chihuahua to Los Ornos, Sinaloa, near the common borders of Sinaloa, Chihuahua, and Durango (Smith and Taylor 1948, Zweifel 1968, Rorabaugh and Hale 2005, Lemos-Espinal and Smith 2007, personal observations). It is unknown from Durango, but given the proximity of the Los Ornos locality to the Durango border and apparent suitable habitat, it may occur in the western mountains of that state. Reports of the species from New Mexico (Linsdale 1933, Little and Keller 1937, Wright and Wright, 1949) and at Rose Creek near Roosevelt Reservoir, Arizona (Little 1940) were based on misidentified specimens of American Bullfrogs (Stebbins 1951, Zweifel 1968). Fig. 4 shows the distribution in Arizona and Sonora.

Fig. 3: Late stage Tarahumara Frog tadpole, Sierra de la Madera stock.

Fig. 3: Late stage Tarahumara Frog tadpole, Sierra de la Madera stock.

The species was first reported from Arizona by Berry Campbell (1931), who found them on 18 June 1931 “near Pena Blanca Springs, Santa Cruz County” at a series of pot holes as well as at an “old tumbled-in mine”. Whether this is the Peña Blanca Spring that is currently along Ruby Road at the crossing of Peña Blanca Canyon, or whether it refers to Alamo Spring or the spring that is now inundated by Peña Blanca Lake is unknown. Wright and Wright (1949) were the first to definitively report Tarahumara Frogs from nearby Alamo Canyon. In 1949, Stebbins (1951) found them in Sycamore Canyon about 10 km west of Peña Blanca Spring. In 1948 they were found in Tinaja Canyon in the Tumacacori Mountains (Williams 1960); and during 1970-1974 Tarahumara Frogs were discovered in Big Casa Blanca, Gardner, and Adobe canyons in the Santa Rita Mountains (Hale et al. 1977, Hale and May 1983). Arizona localities are described by Hale and May (1983).  Refugia populations of this frog have been established outside of its native range in ponds at the International Wildlife Museum in Tucson and a canyon in the Castle Dome Mountains, Kofa National Wildlife Refuge, Yuma County, Arizona, as part of a conservation program (see “Conservation” below). Fig 4 T Frogjpg

The Tarahumara Frog is an inhabitant of rocky streams and plunge pools in canyons and arroyos located within tropical deciduous forest, foothills thornscrub, semi-desert grassland, oak woodland, and pine‑oak woodland. Within Arizona and the 100-Mile Circle, localities are characterized by semi-desert grassland, oak woodland and savanna, and pine-oak woodland.  Plunge pools in stream reaches with low mean flows (< 6 liters per second) and relatively steep gradients (> 60 m per km of stream) provide the best breeding sites. Perennial reaches and pools are needed for breeding.

Activity and Reproduction

In southern and lowland sites, Tarahumara Frogs may be active nearly year round. In Arizona, they are most active from April into October and are active by day and at night. In Big Casa Blanca Canyon, Hale and May (1983) found that emergence of frogs begun in early April when water temperatures rose above 100 C. During the dry season, frogs congregate in areas of perennial flow and at drought-resistant plunge-pools and tinajas. When the rains come in June or July, frogs migrate up- and downstream to take advantage of increased available habitat. In the fall they tend to return to areas of permanent water. Breeding occurs primarily towards the end of the dry season (April-May) in perennial plunge pools and tinajas, but reproduction has also been documented in late summer. Clutches of 2,200 or more eggs (Stebbins 1951) are laid in spherical masses, typically deposited on bedrock in quiet pools (Fig. 5). Tadpoles take up to two years to metamorphose, but in captivity metamorphosis occurs in as little as three months. Despite lacking vocal sacs or slits, males and females, and juveniles and adults, manage to emit a variety of soft snores, whines, and squawks any time water temperatures are 150 C or above (Rorabaugh and Elliott 2006). These calls are not always associated with breeding activity.

Fig. 5: Tarahumara Frog and egg mass, Big Casa Blanca Canyon, Santa Rita Mountains, Arizona.

Fig. 5: Tarahumara Frog and egg mass, Big Casa Blanca Canyon, Santa Rita Mountains, Arizona.

The Tarahumara Frog is typically found in water or on the water’s edge, but they are certainly capable of dispersal overland and along drainages. A female marked and released in Big Casa Blanca Canyon in 2004 as part of a reestablishment program was found at an impoundment in a tributary of Adobe Canyon in 2008. The shortest route possible between the two sites is 1.6 km, and the most likely routes all involve at least some overland (not along drainages) travel. This same frog was found in Gardner Canyon in 2013 at a straight line distance of about 3.4 km across rugged terrain from the Adobe Canyon site (King et al. 2013). Again, the frog likely travelled overland considerable distances to make this trek. Within Big Casa Blanca Canyon, Hale and May (1983) documented movements up to 1885 m.

Diet

Tarahumara Frogs are likely opportunistic carnivores. Items reported in the diet are diverse, including various invertebrates (e.g. beetles, moths, water bugs, scorpions, centipedes, grasshoppers, spiders, and caddisflies), as well as a juvenile Sonoran Mud Turtles, snakes, including a Yaqui Black-headed Snake, and Sonora Chub (Gila ditaenia) (Zweifel 1955, McDiarmid 1968, Hale and May 1983). Cannibalism occurs in captive colonies and is suspected in the wild. In the Castle Dome Mountains, Arizona, Tarahumara Frogs occasionally eat European Honey Bees (Apis mellifera), but do so only rarely, despite the fact that these insects are often in abundance at the water’s edge. I watched a Tarahumara Frog at an outdoor captive facility eat a large orange hornet (Vespidae).  Tadpoles are likely omnivorous with a strong tendency towards algivory. In captivity, tadpoles ate spinach, sliced vegetables, fish food, algae, and boiled egg whites. 

Conservation

The Tarahumara Frog is listed as vulnerable on the IUCN’s Red List, but is neither found on Mexico’s list of special status species nor on the U.S. list of threatened and endangered species.  Under Arizona Game and Fish Department (AGFD) regulations, it is illegal to collect or possess a Tarahumara Frog without specific permits.

On 7 April 1974, Clay May and Darrell Frost observed 19 dead Tarahumara Frogs in Sycamore Canyon below Yanks Spring, Pajarito-Atascosa Mountains, Arizona. Several live but lethargic Tarahumara Frogs were also observed, and the skin on top of the head of some individuals was dry.  Two live leopard frogs showed no escape movements. However, when Steve Hale visited the canyon in August, frogs were abundant and appeared healthy. But, that was the last time Tarahumara Frogs were observed in Sycamore Canyon (Hale and May 1983). In 1950 at Peña Blanca Spring, Richard Zweifel found the area had been developed into a campground; no Tarahumara Frogs were observed, but Zweifel found them at Alamo Spring (R.G. Zweifel field notes reported in Hale and May 1983). The species was last observed at Alamo Spring in 1970 by Clay May. The construction of Peña Blanca Lake in 1957 and introduction of American Bullfrogs were probably further stressors that made that area poor habitat for the Tarahumara Frog (Hale and May 1983). American Bullfrogs were stocked in Peña Blanca Lake from 1968-1971; however, UAZ museum specimens from the lake collected in 1968 before the stocking began and 1967 from nearby Summit Tank prove that American Bullfrogs were already in the area. Frogs were absent from Tinaja Canyon in the Tumacacori Mountains and the area provided only limited habitat when Steve Hale visited that site in 1980 (Hale and May 1983).

Decline and ultimately extirpation of Tarahumara Frog populations in the Santa Rita Mountains occurred during 1977-1983. In October 1977 a very strong tropical storm drenched the area, dropping 194 mm of rainfall on Patagonia from 6-9 October. Big Casa Blanca and adjacent canyons were scoured and littered with debris. When Steve Hale surveyed Big Casa Blanca Canyon in the spring of 1978, no juvenile frogs from the 1977 cohort were found. However, many tadpoles survived the flood and metamorphosed frogs were observed in 1978 and 1979.  Yet in July 1980 no tadpoles or metamorphosed frogs were found. Only a few frogs persisted in the canyon until 28 May 1983 when Steve Hale and Jim Jarchow found a large, dead female frog at the String of Pools reach (Hale and May 1983). That was the last Tarahumara Frog observed in Arizona until recent reestablishment efforts. Similar die offs and population loss were documented at several sites in Sonora beginning in the early 1980s (Hale et al. 2005).

Possible causes of population decline and loss include chytridiomycosis, cadmium or other heavy metal poisoning, winter cold, flooding or severe drought, habitat alteration, and predation by non-native predators (Hale and Jarchow 1988, Hale et al. 1995, Hale 2001). Six of eight frogs examined from those collected during the die off at Sycamore Canyon in 1974 tested positive for Batrachochytrium dendrobatidis (Bd), the organism that causes the fungal skin disease chytridiomycosis (T. Jones, pers. comm.). In retrospect, Hale et al. (2005) found that the condition of frogs found during the die off in Big Casa Blanca Canyon was consistent with symptoms of chytridiomycosis. They also found that frogs from several declining or extirpated populations in Sonora tested positive for Bd, although some populations there were apparently persisting with the disease.

The Tarahumara Frog Conservation Team first met in 1992 to discuss reestablishing the Tarahumara Frog back into Arizona. After much planning and coordination, including navigating the rather tedious 12-step reestablishment process required by the AGFD, and obtaining the proper Mexican and U.S. permits, a portion of a Tarahumara Frog egg mass was collected by Steve Hale in May 2000 from the Sierra de la Madera near Magdalena, Sonora (approximately 72 km south of the border), and imported to the U.S. where it was propagated at the Arizona-Sonora Desert Museum and other localities (Rorabaugh et al. 2005).  Refugia populations from this stock were established at the International Wildlife Museum, Tucson, and a canyon in the Castle Dome Mountains, Kofa National Wildlife Refuge, Arizona.

On 26 June 2004, 47 adult, 138 juvenile, and 229 tadpole Tarahumara Frogs were released at four sites in Big Casa Blanca Canyon (Rorabaugh 2005). Additional releases occurred in 2005 and 2006. The frogs reproduced and thrived in the canyon through 2006. However, in the summer of 2006, heavy flooding following the 2005 Florida Fire deposited huge amounts of sediment and cobble in the canyon, filling in many of the breeding pools. This habitat degradation was followed by a major die off in March of 2007. Dead and dying frogs tested positive for Bd (King et al. 2013). In 2008 only three small frogs and 20 tadpoles were found.  None was found in 2009, although a single frog was reported in 2010. The only known wild frog still alive from the 2004-2006 releases is the large female that was found at the Adobe Canyon tributary in 2008 and then again in Gardner Canyon in 2013.

Tarahumara Frogs from the collection site in the Sierra de la Madera tested negative for Bd, suggesting that perhaps the population is naïve to chytridiomycosis. In 2008, additional stock was collected from Rancho El Trigo southeast of Yécora, Sonora, a site where Tarahumara Frogs have persisted with chytridiomycosis since at least 1982. It is hoped these frogs might show some resistance to the disease. In 2012 and 2013 frogs and tadpoles from this stock were released into Big Casa Blanca Canyon. The habitat is still much degraded from post-Florida Fire sedimentation, but considerable habitat for tadpole development still exists. Tarahumara Frogs were also released at Adobe Canyon. In early October 2013, a die off of Tarahumara Frogs was underway in Big Casa Blanca Canyon. Tissue samples are awaiting testing, but the frogs were symptomatic for chytridiomycosis (A. King, pers. comm). Whether enough frogs survive the die off to establish a self-sustaining population will be determined by future monitoring. In spite of uncertainties in the Santa Rita Mountains, planning is underway to reestablish the species at other historical localities in southern Arizona.

Literature Cited

Boulenger, G.A. 1917. Descriptions of new frogs of the genus Rana. Annual Magazine Natural History (ser. 8) 20(120):413-418.

Campbell, B. 1931. Rana tarahumarae, a frog new to the United States. Copeia 1931:164.

Crother, B.I. (editor). 2008. Scientific and standard English names of amphibians and reptiles of North America north of Mexico, with comments regarding confidence in our understanding. Sixth edition. Society for the Study of Amphibians and Reptiles, Herpetological Circular No. 37:1-84.

Crother, B.I. 2012. Scientific and standard English names of amphibians and reptiles of North America north of Mexico, with comments regarding confidence in our understanding, seventh edition. Society for the Study of Amphibians and Reptiles, Herpetological Circular (39):1-92.

Frost, D.R., et al. 2006. The amphibian tree of life. Bulletin of the American Museum of Natural History 297:1-370.

Hale, S.F., and J.L. Jarchow. 1988. The status of the Tarahumara frog (Rana tarahumarae) in the United States and Mexico: part II. Report to the Arizona Game and Fish Department, Phoenix, Arizona, and the Office of Endangered Species, U.S. Fish and Wildlife Service, Albuquerque, NM.

Hale, S.F., and C.J. May. 1983. Status report for Rana tarahumarae Boulenger. Report to the Office of Endangered Species, U.S. Fish and Wildlife Service, Albuquerque, NM.

Hale, S.F., F. Retes, and T.R. Van Devender. 1977. New populations of Rana tarahumarae (Tarahumara frog) in Arizona. Journal of the Arizona Academy of Science 11:134‑135.

Hale, S.F., P.C. Rosen, J.L. Jarchow, and G.A. Bradley. 2005. Effects of the chytrid fungus on the Tarahumara frog (Rana tarahumarae) in Arizona and Sonora, México. Pp. 407-411 in G.J. Gottfried, B.S. Gebow, L.G. Eskew, and C.B. Edminster (compilers), Connecting Mountain Islands and Desert Seas: Biodiversity and Management of the Madrean Archipelago II. Proceedings RMRS-P-36: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fort Collins, CO.

Hale, S.F., C.R. Schwalbe, J.L. Jarchow, C.J. May, C.H. Lowe, and T.B. Johnson. 1995. Disappearance of the Tarahumara frog. Pp. 138‑140 in E.T. LaRoe, G.S. Farris, C.E. Puckett, P.D. Doran, and M.J. Mac (editors), Our Living Resources: A Report to the Nation on the Distribution, Abundance, and Health of U.S. Plants, Animals, and Ecosystems. U.S. Department of the Interior, National Biological Service, Washington, D.C.

King, A.D., M.J. Sredl, H. Hicks, J.C. Rorabaugh, C.M. Akins, K. Smith, C. Crawford, S. Poulin, and J.A. Lemos Espinal. 2013. Evolving expectations: A decade of repatriating Tarahumara Frogs (Lithobates tarahumarae) to Arizona, USA. Poster, Joint Meeting of Ichthyologists and Herpetologists, Albuquerque, NM, 10-15 July 2013.

Lemos-Espinal, J.A., and H.M. Smith. 2007b. Anfibios y Reptiles del Estado de Chihuahua, Mèxico/Amphibians and Reptiles of the State of Chihuahua, Mexico. Universidad Nacional Autónoma de Mèxico y Comisión Nacional para el Conocimiento y Uso de la Biodiversidad. Mexico.

Linsdale, J.M. 1933. A specimen of Rana tarahumarae from New Mexico. Copeia 1933:222.

Little, E.L. 1940. Amphibians and reptiles of the Roosevelt Reservoir area, Arizona. Copeia 1940(4):260-265.

Little, E.L., and J.G. Keller. 1937. Amphibians and reptiles of the Jornada Experimental Range, New Mexico. Copeia 1937(4):216-222.

McDiarmid, R.W. 1968. Variation, distribution and systematic status of the black-headed snake Tantilla yaquia Smith. Bulletin of the Southern California Academy of Sciences 67(3):159-177.

Pauly, G.B., D.M. Hillis, and D.C. Cannatella. 2009. Taxonomic freedom and the role of official lists of species names. Herpetologica 65:115–128.

Rorabaugh, J.C. 2005. Re-establishment of the Tarahumara frog into Arizona, USA. IUCN Re-introduction News 24:43-44.

Rorabaugh, J.C., and L. Elliott. 2006. Calls of the Tarahumara frog. Sonoran Herpetologist 19(12):134-136.

Rorabaugh, J.C., and S.F. Hale. 2005. Rana tarahumarae Boulenger, 1917, Tarahumara frog. Pages 593-595 in M.J. Lannoo (editor), Amphibian Declines: The Conservation Status of United States Species.  University of California Press, Berkeley, CA.

Rorabaugh, J.C., S.F. Hale, M.J. Sredl, and C. Ivanyi. 2005. Return of the Tarahumara frog to Arizona.  Pages 345-348 in G.J. Gottfried, B.S. Gebow, L.G. Eskew, and C.B. Edminster (compilers), Connecting mountain islands and desert seas: biodiversity and management of the Madrean Archipelago II. Proceedings RMRS-P-36, U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fort Collins, CO.

Smith, H.M., and E.H. Taylor. 1948. An annotated checklist and key to the Amphibia of Mexico. U.S. National Museum Bulletin 194:iv + 118 p.

Stebbins, R.C. 1951. Amphibians of Western North America. University of California Press, Berkeley, CA.

Williams, K.L. 1960. Taxonomic notes on Arizona herpetozoa. The Southwestern Naturalist 5(1):25-36.

Wright, A.H., and A.A. Wright. 1949. Handbook of frogs and toads of the United States and Canada.  Third edition, Comstock Publishing Association, Ithaca, NY.

Zweifel, R.G. 1955.  Ecology, distribution, and systematics of frogs of the Rana boylii group.  University of California Publications in Zoology 54:207‑292.

Zweifel, R.G. 1968. Rana tarahumarae. Catalogue of American Amphibians and Reptiles 66:1‑2.

Author: Jim Rorabaugh

Originally published in the Sonoran Herpetologist 2013 26(4):80-85.

For additional information on this species, please see the following volumes and pages in the Sonoran Herpetologist: 1988-91 Collected Papers:91-92; 1999 Jul:73-74; 2002 Aug:85; 2004 Jul:70; 2004 Nov:102-106.

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