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The following account is modified from Amphibian Declines: The Conservation Status of United States Species, edited by Michael Lannoo (©2005 by the Regents of the University of California), used with permission of University of California Press. The book is available from UC Press.

Rana berlandieri Baird, 1854(a)
            Rio Grande Leopard Frog

James C. Rorabaugh¹

1. Historical versus Current Distribution.  Rio Grande leopard frogs (Rana berlandieri) occur from central and western Texas and the Pecos River drainage in Eddy County, southeastern New Mexico, south along the Atlantic slope through at least southeastern Mexico (Platz, 1991; Degenhardt et al., 1996; Conant and Collins, 1998; Dixon, 2000).  Hillis et al. (1983) considered the southern limit of the distribution to be near Veracruz and frogs from farther south in the Campeche region to be Rana brownorum (= R. berlandieri brownorum, Sanders, 1973).  Frost (1982) noted populations of “berlandieri-like frogs of uncertain taxonomic affiliation” from farther south in Mexico, Guatemala, Honduras, and Costa Rica.  Platz (1991) considered specimens from as far south as northeastern Nicaragua to be Rio Grande leopard frogs, but recognized no subspecies.  Lee (1996) considered frogs in southwestern Campeche, Tabasco, and southern Veracruz to be R. b. brownorum, and frogs from farther south on the Yucatán Peninsula to be R. b. berlandieri.  Rio Grande leopard frogs are currently extant throughout their historical range and are well established as an introduced species in Arizona on the Gila River drainage and associated croplands from Phoenix to the Colorado River confluence; on the Colorado River, Arizona–California near Yuma, Arizona; in the Imperial Valley of southeastern California; and on the Rio Colorado, Sonora, and Baja California Norte, Mexico (Platz et al., 1990; Jennings and Hayes, 1994b; Miera and Sredl, 2000; Rorabaugh et al., 2002).

2. Historical versus Current Abundance.  No historical information.  However, in New Mexico, R.D. Jennings (1987) found Rio Grande leopard frogs to be most abundant at sites with large, flowing springs that formed pools along the spring run.  On the Yucatán Peninsula, they are “common” in virtually all freshwater habitats, but seem to reach especially high densities in open, disturbed situations (Lee, 1996).  Numbers of frogs at some sites apparently vary greatly among years and seasons (Jung et al., 1999; personal observations; C. Painter, personal communication).

3. Life History Features.

            A. Breeding.  Reproduction is aquatic.

                        i. Breeding migrations.  Breeding migrations are unknown in Rio Grande leopard frogs.  In warm climates, the species may breed year-round (Garrett and Barker, 1987; Davidson, 1996).  However, in New Mexico, breeding probably peaks early in the spring, and calling has been heard from April–August (R.D. Jennings, 1987; Degenhardt et al., 1996).  In central Texas, the species breeds in spring and fall, but in areas of sympatry with other leopard frog species, Rio Grande leopard frogs breed in fall and early winter (Hillis, 1981; but see Platz, 1972).  Ideuer (1979) reported that the Rio Grande leopard frog breeding season covers at least 11 mo in central Texas.  On the Yucatán Peninsula, breeding is associated with the rainy season (Lee, 1996); tadpoles have been observed from February–September, and newly metamorphosed frogs have been found in March–April (Campbell, 1998).  In California and Arizona, introduced Rio Grande leopard frogs probably breed nearly year-round.  Individuals have been heard calling as early as 10 February and as late as 29 October.  A pair in amplexus was observed on 28 October near Yuma, Arizona (personal observation).  In an experimental setting, Oldham (1974) found no evidence that female Rio Grande leopard frogs were attracted to playbacks of recorded mating calls.  Blair (1961a) described the phenology and other aspects of the breeding ecology of "Rana pipiens" near Austin, Texas.  However, it is unclear as to whether he was working with Rio Grande leopard frogs or southern leopard frogs (Rana sphenocephala). 

                        ii. Breeding habitat.  In Texas, Rio Grande leopard frogs are found in arid regions along streams or rivers and near cattle tanks, ponds, or ditches (Garrett and Barker, 1987).  Hillis (1981) found that in central Texas the species breeds almost always in pools along flowing streams or rivers; but breeding also occurs in artificial ponds and tanks.  In New Mexico, Rio Grande leopard frogs generally are found in clear, flowing streams or permanent pools in intermittent stream drainages that originate from springs.  Animals are occasionally found in cattle tanks, as well (Fritts et al., 1984; R.D. Jennings, 1987).  At Black Gap Wildlife Management Area, Brewster County, Texas, Rio Grande leopard frogs were found only in earthen cattle tanks (Axtell, 1959).  In northern Guatemala and the Yucatán Peninsula, including Belize, Rio Grande leopard frogs usually occur at permanent water in wet, moist, or dry tropical forest (Campbell, 1998).  They are a common inhabitant of a cienega (wetland) on the northern coast of the Yucatán Peninsula, where the water is possibly brackish, and in cenotes (natural wells resulting from collapse of the limestone roofing of subterranean chambers) in the northern peninsula (Lee, 1996).  In Arizona and California, Rio Grande leopard frogs are typically found on the edges of large slow-moving rivers, in agricultural ditches, drains, canals, and sumps; and in one case, they were found in a fish hatchery (Platz et al., 1990; Jennings and Hayes, 1994b; Rorabaugh et al., 2002).  Hutchison and Hazard (1984) examined diel and seasonal cycles of erythrocytic organic phosphates in frogs they called Rio Grande leopard frogs, which may have some relevance to use of, or behavior in, hypoxic environments.  However, the frogs used in their experiments were from Sinaloa, Mexico, outside of the range of Rio Grande leopard frogs (the frogs used were Rana forreri).

            B. Eggs.

                        i. Egg deposition sites.  Egg masses in Eddy County, New Mexico, were 7–9 cm across and attached to emergent vegetation in 9–15 cm deep, quiet water along a stream (Degenhardt et al., 1996).

                        ii. Clutch size.  Unknown; however, clutches of other leopard frog species typically contain from hundreds to several thousand eggs. 

            C. Larvae/Metamorphosis.

                        i. Length of larval stage.  Tadpoles are known to overwinter in Texas (Hillis, 1982) and Arizona (personal observations).  Bragg (1961) reported on comparative behavior and development of “Rana pipiens berlandieri” and two other anurans.  However, the study was conducted near Norman, Oklahoma, where Rio Grande leopard frogs do not occur (he was probably working with the plains leopard frog, Rana blairi).

                        ii. Larval requirements.

                                    a. Food.  Tadpole stomachs in Texas contained blue green algae, green algae, inorganic particles, and many diatoms.  The predominance of diatoms is probably due to indiscriminate feeding of bottom detritus and the indigestibility of diatoms.  In the laboratory, larvae are cannibalistic (Hillis, 1982).

                                    b. Cover.  Probably necessary to avoid currents.  Tadpoles are probably transported passively downstream in drainages.  Tadpoles are adapted to life in streams (Hillis, 1982) and will swim upstream against a current (Wassersug and Feder, 1983).  Rio Grande leopard frog tadpoles will supplement cutaneous gas exchange by gulping air at the water surface.  Air breathing contributes substantially to total oxygen uptake, even in normoxia, and increases stamina of tadpoles under hypoxic conditions (Feder, 1983a; Wassersug and Feder, 1983).  Maness and Hutchison (1980) reported on heat "hardening" or acute adjustment of thermal tolerance in Rio Grande leopard frogs; however, the animals used in their experiment were from Sinaloa, Mexico, and thus were probably Rana forreri.

                        iii. Larval polymorphisms.  Unknown.

                        iv.  Features of metamorphosis.  Although variable across their range, breeding occurs over a period of a few to many months each year (see "Breeding Migrations" above).  It is not unusual to find tadpoles of different size classes in the same body of water (Jennings, 1985), and newly metamorphic frogs can be found over an extended time period during warm seasons.  In areas of hybridization between Rio Grande leopard frogs and southern leopard frogs (R. sphenocephala) in Texas, the former metamorphose earlier than either hybrids or southern leopard frogs (Kocher and Sage, 1986).

                        v. Post-metamorphic migrations.  Unknown.

            D. Juvenile Habitat.  No differences have been described between adult and juvenile habitat use. 

            E. Adult Habitat.  See "Breeding habitat" above.  The presence of holes or burrows where frogs can take refuge may be an important habitat feature (Jennings and Hayes, 1994b).

            F. Home Range Size.  Unknown.

            G. Territories.  Playback of mating trills of Rio Grande leopard frogs typically elicits chuckle calling, which is probably associated with male territorial behavior (Mecham, 1971; Gambs and Littlejohn, 1979). 

            H. Aestivation/Avoiding Dessication.  Rio Grande leopard frogs are apparently active throughout warm periods and seasons.  No periods of aestivation have been described.

            I. Seasonal Migrations.  No seasonal migrations have been described; however, individuals have been observed to disperse at least 1.6 km from any known water source during the summer rainy season in Arizona (personal observations), and after the first rains in the Yucatán Peninsula, frogs have been collected several km from water (Campbell, 1998).  In New Mexico, R.D. Jennings (1987) noted collections of Rio Grande leopard frogs from intermittent water sources and suggested these were frogs that had dispersed from permanent water during wet periods. 

            J. Torpor (Hibernation).  Rio Grande leopard frogs are inactive during the cold winter; although in warmer areas they may be active year-round.  In Arizona, active Rio Grande leopard frogs have been observed as early as 9 January and as late as 29 October.

            K. Interspecific Associations/Exclusions.  In New Mexico, Rio Grande leopard frogs were not found in association with other anurans, although several anuran species were found nearby (R.D. Jennings, 1987).  At Big Bend National Park, Texas, Rio Grande leopard frogs occurred with low-density American bullfrog (R. catesbeiana) populations.  In Texas, Hillis (1981) found areas of sympatry between Rio Grande leopard frogs and southern leopard frogs in McLennan and Falls counties, and between Rio Grande leopard frogs and plains leopard frogs in Brown, Coleman, and Comanche counties.  In areas of sympatry, habitat, temporal, and behavioral differences among ranid species may act as premating isolating mechanisms.  However, hybridization between Rio Grande leopard frogs and southern leopard frogs occurs in central Texas (Sage and Selander, 1979; Kocher and Sage, 1986) and between Rio Grande leopard frogs and plains leopard frogs in Coke and Mitchell counties, Texas (Platz, 1972).  At 13 sites in central Texas where Rio Grande leopard frogs hybridized with southern leopard frogs, the hybrid zone appeared to be stable over a 3–5-yr period (Kochler and Sage, 1986).  Platz (1981) found Rio Grande leopard frogs replacing plains leopard frogs in Coke and Mitchell counties, Texas, during 1969–‘75.  Rio Grande leopard frogs are often found in association with numerous predatory fish species (R.D. Jennings, 1987; Rorabaugh et al., 2002).  In California and Arizona, Rio Grande leopard frogs commonly occur with Woodhouse’s toads (Bufo woodhousii) and American bullfrogs; however, Rio Grande leopard frogs appear to thrive in habitats that support limited numbers of bullfrogs (Jennings and Hayes, 1994b; personal observations).  Rio Grande leopard frogs are found occasionally with Great Plains toads (B. cognatus), Sonoran Desert toads (B. alvarius), and Couch’s spadefoot toads (Scaphiopus couchii) in Arizona (personal observations).

            L. Age/Size at Reproductive Maturity.  Unknown.

            M. Longevity.  Unknown.

            N. Feeding.  Degenhardt et al. (1996) note that Rio Grande leopard frogs probably feed on a variety of insects and invertebrates.  In Texas, frog stomachs often contained small leopard frogs (Platz et al., 1990).

            O. Predators.  In New Mexico, checkered garter snakes (Thamnophis marcianus) prey on Rio Grande leopard frog tadpoles and metamorphic animals, and predation by American bullfrogs and fishes was identified as a potential threat to the species (R.D. Jennings, 1987b).  Sanders and Smith (1971) suggest crayfish, turtles, fishes, birds, small mammals, and man prey on Rio Grande leopard frogs.  An adult aquatic beetle (Cybister fimbriolatus) preyed upon a Rio Grande leopard frog tadpole near Austin, Texas, and larvae and adults of this beetle, and early instar larvae of another beetle (Hydrophilus triangularis), preyed upon tadpoles in the laboratory (Ideker, 1979).  Aggregations of tadpoles near shorelines may increase predation rates by grackles (Quiscalus mexicanus; Ideker, 1976).  Swimming and air breathing increased the rate at which Rio Grande leopard frog tadpoles were attacked by painted turtles (Chrysemys picta; Feder, 1983).  I watched a hunter gig a large Rio Grande leopard frog near Yuma, Arizona.

            P. Anti-Predator Mechanisms.  Frogs seek shelter under rocks and in streamside vegetation during the day.  If startled while active, individuals quickly hop into the water or thick vegetation (Degenhardt et al., 1996; personal observations).  Where Rio Grande leopard frogs are found in association with predatory fishes in New Mexico, dense aquatic vegetation that could serve as cover for tadpoles and egg masses was typically present (R.D. Jennings, 1987).  Burst swimming is used by tadpoles to avoid predation by turtles (Feder, 1983b).

            Q. Disease.  In 1992–‘93, M. Sredl (personal communication) noted a die-off of Rio Grande leopard frogs at a pond near Phoenix, Arizona.  Dead and moribund frogs were symptomatic for “red-leg,” a bacterial infection.  Histological analysis of dermal tissues demonstrated the presence of chytridiomycosis (Sredl and Caldwell, 2000b), a fungal disease implicated in declines of anurans in Australia, Central America, and elsewhere (Berger et al., 1998).

            R. Parasites.  Two species of mites, Hannemania hylae and H. sp. were found on Rio Grande leopard frogs in Big Bend National Park, Texas (Jung et al., 2001).  Guillen-Hernandez et al. (2000) describe trematodes (digeneans) in Rio Grande leopard frogs collected from Los Tuxtlas, Veracruz, Mexico.  A tetrathyridia (Mesocestoides sp.) was found in the liver and mesenteries of a single specimen of Rio Grande leopard frog from Texas (McAllister and Conn, 1990).

4. Conservation.  Rio Grande leopard frogs have no status under the Federal Endangered Species Act or C.I.T.E.S., but are considered a Species of Special Protection by the Government of Mexico (Secretaria de Desarrollo Social, 1994).  The species is not considered a Species of Special Concern, Threatened, or Endangered by the states of Texas, New Mexico, Arizona, or California.  Rorabaugh and Sredl (in press) recommend development of strategies to curb the ongoing invasion of this species into Arizona and California as a means to protect native anurans and other species that may be vulnerable to predation, competition, or diseases carried by Rio Grande leopard frogs.

¹James C. Rorabaugh
U.S. Fish and Wildlife Service
2321 West Royal Palm Road
Phoenix, Arizona 85021-4915
Jim_Rorabaugh@fws.gov

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 20 Apr 2024.

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