Plains Leopard Frog

Lithobates blairi (Mecham, Littlejohn, Oldham, Brown & Brown, 1973)

The dorsum is tan to brown but may be green with dark spots that lack a white border.  The snout frequently has a single spot; the tympanum usually has a white, centered spot; the dorsolateral line is interrupted at the groin.  These characteristics, combined with a yellow wash on the ventral surface of the legs and belly, all combine to distinguish this frog from other Arizona leopard frogs. Adults reach 51 to 114 mm SUL, with the western populations having a larger body size.  Tadpoles metamorphose at 27 to 30 mm SUL. Scott and Jennings (1985) described Plains Leopards Frog tadpoles at stage 40. The body length 27 mm; total length 81 mm: the dorsum and sides are olive with numerous obscure dark dots giving a gray-brown effect; belly and throat shiny white with a pink ­bronze wash ventrolaterally. Tail musculature pale olive with large bronze blotches; tail fins clear olive with indistinct bronze blotches giving an appearance of pale spots; entire tail covered with indistinct dark smudges and blotches. Peritoneum of the lateral body wall is black dorsally shading to gray laterally and white ventrally; peritoneum covering dorsal body muscle is black; lungs dark gray. Iris black with gold flecks; flecks densest around pupil. No cross-like pattern in iris.

Voice. Stebbins (1985) describes the advertisement call as two to four guttural chuck like notes, tuck, tuck, tuck, tuck each lasting less than a second. He also reports grunt and grinding notes are produced. Brown (1991) published an audiospectragram of the advertisement call of Rana blairi from Hudson, McLean Co., IL.

Distribution and Habitat. Lithobates blairi is a Great Plains species that followed the prairie peninsula eastward into the Midwest. It expanded into grassland habitats during the drier periods between glacial expansions. and ranges as far east as central Indiana. On the western edge of the range they are present in southern Arizona, central New Mexico, central Colorado. The northern edge of the distribution is in southern South Dakota, central Iowa and northern Illinois. The southern edge of the range is in north central Texas, southern New Mexico, and southeast Arizona with central New Mexico and Arizona population represented by disjunct populations (Brown, 1992, Brown et al. 1993, Conant and Collins 1998). In New Mexico, Plains Leopard Frogs reach an elevation of 2,130 m near Sierra Blanca, Lincoln County (Stebbins, 1985 Degenhardt et al. 1996). In Arizona, an isolated population is present on the western side of the Chiricahua Mountains and adjoining Sulfur Springs Valley, at elevations of 110–2,590 m (Stebbins 1985). A single individual found near Flagstaff may represent an introduction of the species in northern Arizona (Clarkson and Rorabaugh, 1989). Hammerson (1982a, 1999) noted Colorado populations only go to 1,828 m in elevation, undoubtedly due to the higher latitudes of those populations. Overwintering may occur at upland sites or the frog may overwinter in the mud and benthic debris of ponds and streams, which they use for reproduction.  In Arizona it uses grasslands, oak savanna, and oak–pine forests in Arizona. For reproduction it uses potholes, pools in rocky canyons, streams, and livestock tanks.  After reproducing, it moves away from water to feed and replenish its stores of fat (Crawford et al. 2005). Grant et al. (2018) suggest that the Plains Leopard Frog larvae would survive better than the Northern Leopard Frog in areas that flood on a regular basis. Scott and Jennings (1985) report this frog as most common in muddy tanks and rivers. Frost and Bagnara (1977) suggest the R. blairi-like leopard frogs of southeastern Arizona are essentially identical to known R. blairi from the central United States. But note that the prominent olive-green inner-spot coloration observed in R. blairi in Arizona might be of taxonomic significance. The extreme western distribution for the main body of the species in the central United States is presently unresolved, their field observations imply that a distributional discontinuity (possibly as great as 350 km) probably exists between the main body of the species and the populations of southeastern Arizona. The area comprising extreme southwestern New Mexico is largely Chihuahuan Desert, and permanent surface water is practically non-existent in the low mountain ranges and basins of the region except where irrigation practices have been initiated. At the present time, this region appears to be too arid to support populations of R. blairi. Climatological indicators (Stockton and Fritts 1970) suggest that this general area was less xeric in historic times, and, accordingly, the region might have supported R. blairi populations continuous with those of extreme southeastern Arizona. There presently is little or no permanent surface water in the Sulphur Springs Valley except that supplied by wells for irrigation and ranching. Turkey Creek and Rucker Creek are intermittent streams (with numerous permanent pools) that drain the western slopes of the Chiricahua Mountains. Following exceptionally heavy rains, Turkey Creek communicates with irrigated areas of the valley for short periods of time (hours). They surmise that the present population of blairi on Turkey Creek represents a relictual population which in turn seeded Sulphur Springs Valley populations subsequent to the relatively recent introduction of irrigation practices in the valley.

Reproduction.  Breeding sites are water-filled ditches, ponds, streams, temporary pools, marshes, and canyon pools that are fish-free.  Males call from the surface of the water with a series of clucks each lasting 0.48 to 0.89 seconds and a three-note trill call that lasts 0.5 to 1 second. It is shorter and slower than the Northern Leopard Frog. Breeding can occur anytime from February through October, depending on local environmental conditions (Axtell and Haskell 1977, Black and Sievert 1989, Caldwell and Glass 1976, Collins 1982, Collins and Collins 1991, Dunlap and Kruse 1976, Ehrlich 1979, Frost and Bagnara 1977, Frost and Platz 1983, Gray and Stegall 1986, Hammerson 1982a, Hillis 1981, Johnson, 1977, 1987; Lynch 1978,1985; Post and Pettus 1967, Rundquist et al. 1978 Scott and Jennings 1985, Stebbins 1985). Hammerson (1982a) sometimes found newly laid eggs and large tadpoles together, and he suggested that breeding might occur more than once a year at a given site. Males frequently call in a floating position at the water surface (Black and Sievert 1989, Hillis 1981). Frost and Bagnara (1977) played tape recordings of mating calls of blairi to sexually active male blairi in the evening before calling began. Males responded vocally to these recordings, and they also often turned to face (and sometimes approached) the source of the recording. However, playbacks of mating calls of Rana chiricahuensis failed to evoke any response from male blairi under similar circumstances. Breeding has been reported from February–October (Brown 1992, Degenhardt et al. 1996). Scott and Jennings (1985) report New Mexico Plains Leopard Frog eggs in May, medium sized tadpoles in April through August, large tadpoles April through September, and transforming tadpoles May through August. Tadpoles can metamorphose at any time during the summer dependent upon when eggs were laid (Hammerson, 1982a). However, when eggs are laid in late summer or fall, tadpoles overwinter and transform the next spring (Axtell and Haskell 1977, Collins 1982, Collins and Collins 1991, Hammerson 1982a, Johnson 1987, Lynch 1985, Scott and Jennings 1985). Newly metamorphosed juveniles averaged 27 mm in length in Missouri (Johnson, 1987), and the supralabial stripe is often well defined in the young (Stebbins, 1985). The usual annual activity period was reported by Collins (1982), Collins and Collins (1991), Hammerson (1982a), and Johnson (1987) to extend from early spring (Feb.-Apr.) into fall (Oct.). Hammerson (1982a) noted that in the fall, large numbers of R. blairi gathered at some ponds used as over-wintering sites. Sometimes the species is active in winter (Collins 1982, Collins and Collins 1991). Winter activity under ice in Oklahoma was reported by Black et al. (1976). Smith et al. (1983) noted four frozen R. blairi in December that had apparently died after leaving a Missouri pond through holes in the ice. Frost and Bagnara (1977) found that after being disturbed, R. blairi often sought refuge in vegetation surrounding bodies of water. Gillis (1979) observed that when R. blairi were subjected to dehydration stress, they assumed a water-conservation posture (legs tucked near body, ventral surface pressed on substrate). Scott and Jennings (1985) report New Mexico Plains Leopard Frog eggs in May, medium sized tadpoles in April through August, large tadpoles April through September, and transforming tadpoles May through August. Clutch sizes are 4,000–6,500 eggs that require a few days to three weeks of incubation to develop into tadpoles. Tadpoles usually metamorphose in midsummer.  However, late-hatching tadpoles may overwinter and transform the following spring. Larval Survival and Hybridization. Parris (2000) examined relative fitness of parental and hybrid leopard frogs by measuring larval performance in artificial ponds and laboratory containers. Effect of a variable hydroperiod on growth, development, and survival was used to assess larval responses to a desiccating aquatic environment. Larvae for the artificial pond experiment were obtained from field-collected egg masses of Rana blairi and R. sphenocephala (a Gulf Coastal Plain species). Artificial crosses with adult animals produced larvae of one parental and three hybrid genotypes for laboratory performance assays. Experimental pond drying significantly reduced survival for both parental species. Rana blairi had higher survival than R. sphenocephala across all treatments. Both species reduced larval period lengths when exposed to a drying environment relative to constant water levels. The laboratory experiment revealed Backcross2 hybrid larvae exhibited longer larval period lengths than parental R. sphenocephala and certain F1 hybrid genotypes in the drying environment. Proportion of survivors metamorphosing was greatest for the F1 hybrid genotype SB and lowest for the Backcross2 hybrid genotype. Consequently, advanced-generation hybrid genotypes (i.e., Backcross2) did not perform well in desiccating environments. Direct measurements of important fitness components of parental and hybrid genotypes are critical for determining the evolutionary potential of natural hybridization. Hybridization occurs between Northern Leopard Frog and Plains Leopard Frogs where these species co-occur. The Plains Leopard Frogs is native to the southeastern portion of Arizona with one record from Ashhurst Lake near Flagstaff. This record may represent an introduction (Rorabaugh, 2005) see below. Predators. Fishes, American Bullfrogs, gartersnakes, raptors, prairie dogs, raccoons, opossums, and skunks have all been reported to feed on this species.  Declines in numbers and extirpated populations are likely due to habitat loss, the invasive bullfrog, and chemicals (herbicides, pesticides, and other agrochemicals.  In a 2014 survey done by the Department of Defense, this species was not found to be carrying the Bd fungus. There is no open season on this species.

Disease. Christman and Jennings. (2018) found 11% of the individuals tested in New Mexico were infected with Bd.

Declines and Conservation. Clarkson and Rorabaugh (1989) suggested losses of R. blairi in Arizona may be the result of fragmentation of its insular distribution via groundwater pumping, agricultural development, and introductions of exotic amphibians and fishes. Sulphur Springs Valley has no through-flowing streams, and most localities surveyed were intermittent man-made stock tanks. Some sites previously reported for the species were dry when they examined them. One locality had a large population, but the presence of bullfrogs may reduce the chances of its continued existence, if indeed bullfrogs are a factor in declines of ranid frog species in western North America (see Hayes and Jennings, 1986). The record of R. blairi from Ashurst Lake southeast of Flagstaff, Coconino Co., Arizona, by Platz may represent an introduction or indicate that R. blairi was once more widespread in montane localities in Arizona. The idea of the bullfrog as the reason for the loss of this species is possible but puzzling given that the Plains Leopard Frog’s natural distribution is shared with the American Bullfrog.

Taxonomy. Rana blairi was described by Mecham et al. (1973:3) based upon the holotype UMMZ 131690 from the type locality 1.6 km W New Deal, Lubbock County, Texas, USA. Dubois (1992:332) used the combination Rana (Pantherana) blairi. Hillis and Wilcox (2005:305) used the combination Rana (Novirana, Sierrana, Pantherana, Scurrilirana) blairi. This was considered an invalid name formulation under the International Code of Zoological Nomenclature (1999) as discussed by Dubois (2007:395). Hillis and Wilcox (2005:305) used the combination Rana (Novirana) blairi. Frost et al. (2006:369) place the species in the genus Lithobates, using the combination Lithobates blairi. Dubois (2006:829) used the combination Lithobates (Lithobates) blairi. Hillis (2007:335) implied the combination Rana (Scurrilirana) blairi. Fouquette and Dubois, 2014:405 used the combination Rana (Lithobates) blairi.