Rana berlandieri Baird, 1854(a)
Rio Grande Leopard
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
3. Life History Features.
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
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.
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.
Habitat. No differences have been described between adult and juvenile habitat
Habitat. See "Breeding habitat" above. The presence of holes or
burrows where frogs can take refuge may be an important habitat feature (Jennings and
F. Home Range
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).
Aestivation/Avoiding Dessication. Rio Grande leopard frogs are apparently active
throughout warm periods and seasons. No periods of aestivation have been described.
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.
(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
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.
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).
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.
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).
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
Literature references for Amphibian Declines: The Conservation Status of United States Species, edited by Michael Lannoo, are here.
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