Researchers described Rana kauffeldi as a new cryptic species of leopard frog from the New York City metropolitan area and surrounding coastal regions in 2014 (Feinberg et al. 2014). This species is morphologically similar to two largely parapatric eastern congeners, Rana sphenocephala and R. pipiens. Feinberg et al. 2014 primarily used bioacoustic and molecular data to characterize the new species, but also examined other lines of evidence. The discovery of R. kauffeldi was unexpected in one of the largest and most densely populated urban parts of the world. It also demonstrates that new vertebrate species can still be found periodically even in well-studied locales rarely associated with undocumented biodiversity.
Rana kauffeldi typically occurs in expansive open-canopied wetlands interspersed with upland patches, but centuries of loss and impact to these habitats give some cause for conservation concern. Other concerns include regional extirpations, fragmented extant populations, and a restricted overall geographic distribution. Feinberg et al. 2014 assigned a type locality within New York City and report a narrow and largely coastal lowland distribution from central Connecticut to northern New Jersey (based on genetic data) and south to North Carolina (based on call data).
From Feinberg et al. 2014
Body moderate and robust; head longer than wide. Dorsal outline of snout acuminate; lateral snout profile round. Nares dorsolaterally oriented, slightly protuberant, around two-thirds closer to tip of snout than anterior corner of eye. Canthus rostralis distinct and angular; loreal region steep and slightly concave. Eyes large and protuberant; diameter slightly less than combined eye-to-naris and naris-to-snout distances. Internarial distance nearly equal to eye-to-naris distance. Tympanum distinct and relatively large (>65% diameter of the eye); bordered dorsally and posteriorly by faint supratympanic fold. Distinct dorsolateral fold runs uninterrupted from posterior eye to pelvic insertion of femur. Forearms relatively short and robust; unwebbed fingers; relative length III>I>II>IV. Fingers lack fringes; tips rounded without expansion; subarticular tubercles small, round, and moderately prominent. No palmer tubercles appear present. First finger slightly swollen at base with faint nuptial pad; all other fingers slender. Hindlimbs relatively long, moderately robust; thigh and shank length nearly equal. Relative toe lengths IV>V>III>II>I; toes have rounded tips without expansion; subarticular tubercles small, round, and prominent. Inner tarsal fold connects tarsus to large, distinct, elliptical, elevated inner metatarsal tubercle. Indistinct, small outer metatarsal tubercle faintly evident. Toe IV very long and slender; toe V slightly fringed; webbing present between all toes; webbing formula I1 – 2II1+ – 2⅓III1+ – 3+IV3 – 1V following Savage (2002). Skin on dorsum smooth with several raised folds running between and parallel to dorsolateral folds. Flanks, thighs, and shanks smooth. Ventral surface mostly smooth with papillae-like granulation on groin and thighs. Large, distinct, paired lateral external vocal sacs.
In photographs taken before preservation, dorsal ground color of holotype varies from mint-gray in bright lighting to light olive green in darker conditions. Medium to dark brown spots irregularly distributed across dorsum and lateral body; more elongate or barred on the limbs. Distinct black postorbital patch encompasses dorsal and posterior tympanum along the supratympanic ridge. Labial margins slate gray with light mottling and distinct ivory stripe above the upper margin; terminates under the tympanum (continues to anterior forearm in females). Dark canthal band runs from snout tip through the nare and iris, along outer edge of dorsolateral fold; terminates above the arm. On snout, inner edge of canthal band is paralleled by light brown band that continues through the eyelid to merge with a dorsolateral fold that varies from gold to bronze in different lighting. Iris gold with dark intrusions at corners. Vocal sac slightly darker than surrounding skin. Lower flank of holotype pale with light yellowish-green hues and smaller, lighter spots and mottles; these intrude onto ventral margins, throat, or body in some individuals. Tympanum finely granulated brown color with black flecks; central spot creamy and subtly defined in holotype; bright and well defined or entirely absent in some individuals. Reticulum and anterior ventral margin of thigh dark with distinct light flecks or mottles; off-white in holotype, occasionally bone-white, light yellow or green in some individuals. Ventral limbs of holotype pinkish-gray with scattered mottles; body pale white. Inner tarsal fold and outer metatarsal tubercle are bright white against a dark brown tarsal background; webbing pale gray.
Generally similar to that in life with several notable distinctions. Ground color dark olive green in holotype but can range from tan to dark brown in other specimens (as in paratypes YPM 13559 and 13560). Colored flecks and mottles in life appear white in preservative. Ventral body and limbs of holotype cream, light mottling behind knees. Dorsolateral fold of holotype rust brown; off-white to brown in other individuals. Tympanic spot, when present as in the holotype, typically subtle and grayish white.
From Feinberg et al. 2014
Rana kauffeldi is known from three states (CT, NY, NJ) based on genetic samples (Newman et al. 2012) and seven states (NY, NJ, PA, Delaware [DE], Maryland [MD], Virginia [VA], and North Carolina [NC]) based on bioacoustic sampling reported here. The estimated range from these samples is approximately 780 km, north-to-south, from central CT to northeastern NC. The range is narrow, however, east-to-west, occurs almost entirely within the densely populated I-95 corridor, and is smaller than most if not all other ranid frogs along the eastern North American seaboard. Within the presented range, we depict a core sampling area where gaps in genetic and bioacoustic information were filled by other lines of evidence (e.g., specimens, photographs, geology, or historical literature). Rana kauffeldi appears to occur parapatrically in this core area. Beyond the core area, we depict an extended area of potential occurrence based on habitat features and proximity to known bioacoustic confirmations in DE, MD, VA, and NC. We also note the potential for sympatry with R. sphenocephala (in the south) and R. pipiens (in the north) based on genetic, bioacoustic, and specimen sampling.
Rana kauffeldi has a mesic distribution that is wider in the north and narrows from Trenton, NJ, to the Delmarva Peninsula. This part of the range essentially follows the Delaware River floodplain and the Atlantic Fall Line – the geologic interface between the relatively xeric Atlantic coastal plain where R. sphenocephala occurs, and more interior and upland regions to the west – where R. pipiens occurs. This species is usually abundant where it occurs, but populations in the NY/NJ-metro area tend to be disjunct and isolated from one another and often occur in highly fragmented landscapes with limited connectivity or dispersal opportunities. Rana kauffeldi was generally included within the range of R. sphenocephala prior to its discovery, but northern mainland populations from northeastern PA to central CT may have been included within R. pipiens instead.
We also consider R. kauffeldi to have previously occurred within parts of an apparent extirpation zone that includes most of coastal NY and southern CT. We used multiple lines of evidence to inform this conclusion, including historical locality information (Klemens 1993; Kauffeld 1937; photographs Overton 1949a,b; Villani 1997; call descriptions Overton 1949b, Sherwood 1898; personal communications (A. Sabin and F. C. Schlauch), and museum specimens). Our assessment of museum specimen and photographs included frogs from Long Island (n = 27) and Bronx County, NY (n = 7). Based on our examination, 29 of these 34 frogs were R. kauffeldi. Two other individuals, from xeric parts of Long Island, NY (Suffolk County), appeared to be R. sphenocephala (AMNH 125956, 176153). The remaining three frogs were R. pipiens, two of which (AMNH 106549, 106550) came from the Bronx County site previously noted by Pace (1974) and Klemens et al. (1987), where specimens of R. kauffeldi (AMNH 52342, 106551–10654) were also collected historically. The third was a lone individual from western Long Island, in Queens County, NY (AMNH 36651). We also examined specimens (n = 9) from two presumably extirpated sites in southeastern CT (New Haven County). All were R. pipiens, but neither site is coastal or located within a bottomland riparian floodplain where R. kauffeldi would be expected to occur.
From Feinberg et al. 2014
Little is known about non-breeding activity or dispersal in R. kauffeldi, but leopard frogs have been described as being fairly terrestrial on Staten Island (Mathewson 1955). In our work, we observed individuals on land later in the season, but also noted periods, typically in summer and early fall, when few if any individuals could be found. Diet is not specifically known, but is presumably similar to those reported for other regional leopard frog species.
Individuals may exhibit a limited degree of color change around a general base color that can vary widely between frogs, from light green to dark brown. Holmes (1916) noted that leopard frogs (sensu lato) tend towards darker nocturnal shading and brighter, more vivid diurnal colors (as a putative mode of camouflage). Some degree of seasonal color change also appears to exist in R. kauffeldi; we often observed frogs with darker, drabber color and fainter tympanic spots in the early spring, and more vivid and varied overall color and brighter, more defined tympanic spots later in the season.
From Feinberg et al. 2014
Holotype (YPM 13217) falls within the R. kauffeldi clade in the mitochondrial phylogeny reconstructed by Newman et al 2012. Mitochondrial and nuclear haplotypes are identical to other R. kauffeldi samples. As reported by Newman et al. 2012, R. kauffeldi is genetically distinct from all other regionally occurring spotted ranid frogs (R. sphenocephala, R. pipiens, and R. palustris). The mitochondrial phylogeny suggests that R. kauffeldi is most closely related to R. palustris. Average pairwise mitochondrial sequence divergence (uncorrected p) is similar to genetic divergences between other closely related species in the R. pipiens complex (Newman et al. 2012).
From Feinberg et al. 2014
Rana kauffeldi inhabits a restricted range of mesic lowland habitats that primarily includes coastal freshwater wetlands, tidally influenced backwaters, and interior riparian valley floodplains. This species is typically associated with large wetland complexes composed of open-canopied marshes, wet meadows, and slow-flowing systems with ample open upland and early-successional habitats. Aquatic conditions are usually clear, shallow, and sometimes ephemeral, with emergent shrubs or stands such as cattail, Typha spp., or the invasive common reed, Phragmites australis.
From Feinberg et al. 2014
Rana kauffeldi begins breeding around the same time as R. sylvatica and R. sphenocephala and slightly in advance of R. pipiens and R. palustris. In NY, we have observed migratory activity on rainy nights with above-average temperatures in early February, and have documented the onset of chorusing after several days of above-average temperatures in early-to-mid March. Choruses are most consistent nocturnally, with air temperatures ranging from 10–18°C, but sustained diurnal and nocturnal chorusing is common early in the season and through the initial 2–3 week peak breeding period (late March and early April in NY), especially on warmer days. Thereafter, chorusing tapers to a more episodic nocturnal and precipitation-based regime from mid-April through early June (in NY). We have not observed opportunistic mid-summer chorusing as we and others [26], [71] have for R. sphenocephala, but we have observed occasional second breeding periods with the onset of cooler autumn temperatures and precipitation (late August through November).
During breeding, males congregate in concentrated groups, or possible leks (Pace 1974) that typically include five or more frogs, with as few as 30 cm between individuals. Males call while floating in shallows with emergent vegetation and as little as 20 cm of water. As stated by Mathewson (1955), their calls are low-pitched and do not carry far. This is especially apparent in the presence of louder, higher pitched sympatric species like spring peepers (Pseudacris crucifer). Thus dense aggregations may have compensatory value, especially when faced with noisy conditions (Wollerman 1999) or acoustic competition from other anurans (Wells 2007; Gerhardt and Schwartz 1995; Penna and Velasquez 2011) Egg masses are often clustered in groups or deposited near one another. Porter (1941) and Moore (1949) discussed eggs and embryonic development among specimens (referred to as R. pipiens) from Philadelphia and NJ, respectively, that we consider R. kauffeldi.
From Feinberg et al. 2014
The Atlantic Coast leopard frog (Lithobates kauffeldi) is a species of amphibian that is endemic to the United States.[4] As a member of the genus Rana sensu lato, it is classified as a true frog, with typical smooth skin and a narrow waist. Its range stretches along the northern part of Eastern Seaboard, from Connecticut to North Carolina. The species takes its common name from the speckles on its legs and back reminiscent of a leopard pattern.[3][5]
It is one of several species classified as leopard frogs, distinguished as unique through its mating call, genetic differences,[6] habitat, and morphological distinctions.
The Atlantic Coast leopard frog is one of several species of leopard frogs. Its species name, kauffeldi, is derived from the name of Staten Island herpetologist Carl Frederick Kauffeld, who in 1936 proposed that there could be a third species of leopard frog inhabiting the New York metropolitan area, specifically Staten Island.[7] The author team that described the species in 2014 christened it after Kauffeld in honor of him.
L. kauffeldi is found along the northeastern coast of the United States from central Connecticut to northeastern North Carolina. The north-south range is approximately 780 km long, and the width is about 100 km from the Atlantic shoreline inward. The range narrows as it progressed southward, mostly along the I-95 corridor. The species is thought to inhabit ten states, but the entirety of its distribution and range is not known.[3] It is thought to be extirpated from most of western New York and Long Island.[1]
The Atlantic Coast leopard frog is thought to be sympatric with both the northern leopard frog and the southern leopard frog in the northern and southern parts of its range, respectively. For a time the species remained undiscovered because of its similarity to both of the aforementioned in physical appearance and habitat.[8]
A vector rendition of the range from Figure 1 of Feinberg et al. (2014) showing the range of the Atlantic Coast leopard frog side by side with the previously understood range for the northern and southern leopard frogs is shown here on Wikimedia Commons.[3]
The frogs' coloring ranges from mint-gray to light olive green, and brown spots distribute irregularly across their backs and legs. Dark snout lines run along their heads. They have large eyes and strong legs used for leaping. Coloring has been observed to change between day and night as well as with the seasons, with many individuals taking nocturnal darker tones and diurnal lighter hues.
Adult males have large vocal sacs on either side of the head which are used to produce a mating call. This call is a single and distinct "chuck" sound rather than the repeated "ak-ak-ak" of related species.[3]
The species breeds at a similar time of year as many other leopard frog species. The frogs commence migrations in February and March. As the air temperature rises in March and April, males begin consistent nocturnal choruses of mating calls, though both sustained diurnal and nocturnal choruses have been observed. They float in shallow water in groups of five or more and call to females. The advertisement call does not travel far, which may be a reason for dense groups.
Breeding continues through spring and early summer, peaking in a 2-3 week period in late March and early April in New York. Eggs are laid in clusters.[3]
L. kauffeldi tends to inhabit large wetland areas, such as marshes, wet meadows, or slow-flowing water. Its habitat usually includes clear, shallow water. The species lives in or around open, vegetated spaces as well, with such plants as cattails, reeds, or river shrubs.[3]
The Atlantic Coast leopard frog (Lithobates kauffeldi) is a species of amphibian that is endemic to the United States. As a member of the genus Rana sensu lato, it is classified as a true frog, with typical smooth skin and a narrow waist. Its range stretches along the northern part of Eastern Seaboard, from Connecticut to North Carolina. The species takes its common name from the speckles on its legs and back reminiscent of a leopard pattern.
It is one of several species classified as leopard frogs, distinguished as unique through its mating call, genetic differences, habitat, and morphological distinctions.
