Amphibians of North Carolina
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NC Records

Pseudacris nigrita - Southern Chorus Frog

Taxonomy
Class: Amphibia Order: Anura Family: Hylidae Subfamily: Hylinae
Taxonomic Comments: Pseudacris nigrita hybridizes with P. fouquettei across the Pearl River between Louisiana and Mississippi. The hybrid zone was estimated in 1976 to be from 8.7–14 km wide, but a recent analysis by Engebretsen et al. (2016) show a marked expansion since then, with the estimated width being 350 km. The reasons for this massive expansion is unknown, but may be due to habitat disturbance and alteration from both humans and hurricane damage. These species may be in the process of fusing into one.

Lemmon and Juenger (2017) analyzed 10 contact zones of P. feriarum and P. nigrita across their range and found that these species frequently hybridize in all of the areas surveyed. The frequency of hybridization varies considerably across the contact zones, and ranges from 5% to 31% for F1 hybrids and 11% to 78% for hybrids of undetermined class. Hybridization was particularly high in Virginia and Florida.
Species Comments:
Identification
Description: The adults are small frogs that have slender bodies, slightly enlarged toe pads and granular skin. The head is relatively long and narrow and the snout somewhat pointed. The dorsal ground color is rather drab and can be various shades of olive, gray, brown, or black. Most specimens have three rows of rounded dark spots along the back that may fuse to form longitudinal stripes (Dodd 2013). These are often incomplete and may be missing in some individuals. When present, the mid-dorsal stripe or row of spots tends to extend almost to the tip of the snout, and there is no dark triangular mark between the eyes. A dark band is present on each side of the head that begins near the nostril and widens as it passes through the eye to the shoulder region. It usually passes beyond the shoulder region where it may either continue to the groin or break up before then. The upper lip has a white stripe (sometimes broken) that contrast with the darker band above. The dorsum of the back and front legs are well-banded, and the belly and chest are whitish and unmarked.

The adults vary from around 23-33 mm SUL and the males are slightly smaller than the females. Some of the reported size ranges that were summarized by Dodd (2013) include 23–28 mm SUL (mean = 24.8 mm) for Alabama specimens, 25 and 33 mm SUL (mean = 29.5 mm) for females and 26 and 32.5 mm SUL (mean = 28.3 mm) for South Carolina specimens, and 27-30 mm SUL for females and 25-29 mm SUL for males from south Florida.

The larvae have a uniform black to dark brown body. The dorsal and ventral fins are about the same size or slightly larger than the tail musculature, and are mottled with small dark flecks. The venter is pigmented with a golden or brassy coloration, and the snout is rounded (Dodd 2013).

This species is similar to P. feriarum and can be difficult to distinguish in areas of geographic overlap. Pseudacris nigrita lacks a dark triangular mark between the eyes, tends to have more boldly banded legs, and has an immaculate, whitish venter versus more yellowish venter with dark spots in P. feriarum. The body is less stout and the snout is somewhat more pointed than that of P. feriarum. Most specimens are collected during the breeding season when the males are calling, so voice characteristics are always helpful in sorting out specimens. These species probably hybridize in North Carolina in areas of sympatry (Lemmon and Juenger 2017).
Vocalizations: The advertisement call is a slow metallic ascending trill with 5-10 notes that are readily distinguishable within each trill. Calling rates are temperature dependent, but trills are typically issued every 1-2 seconds, with each trill lasting about 0.4-0.6 seconds or so. Jensen et al. (2008) described the call as resembling a metallic “ik-ik-ik-ik-ik” that resembles a ratchet wrench in use.

In areas in the Coastal Plain where P. nigrita and P. feriarum are sympatric the calls of the two species deviate from the normal calls (Dodd 2013, Mecham 1961). This appears to reflect reproductive character displacement that reduces breeding mistakes with congenerics (e.g., Lemmon 2009, Malone et al. 2014). In areas of overlap, the call of P. nigrita is very slow (11 pulses/sec; call duration of 0.82 sec) relative to populations outside of the zone of overlap. The call of P. feriarum in the zone of overlap also has a conspicuously faster average pulse rate which contrasts with the very slow pulse rate of P. nigrita.
Technical Reference: Dodd (2013)
Online Photos:    Google   iNaturalist
Observation Methods: The adults are most readily observed during the breeding season when they are calling from breeding sites. They are occasionally seen crossing roads on rainy nights.
AmphibiaWeb Account
Distribution in North Carolina
Distribution Comments: The Southern Chorus Frog is found on the Atlantic Coastal Plain from central North Carolina southward to southern Florida. From there the range extends westward through southern Georgia and southern Alabama to the Pascagoula River in southern Mississippi. A disjunct population occurs in southeastern Virginia. In North Carolina, populations are found from a line from Pitt and Beaufort counties westward to Johnston County, then southwestward to the South Carolina border.
Distribution Reference: Beane et al. (2010), Dodd (2013), Lemmon et al. (2007)
County Map: Clicking on a county returns the records for the species in that county.
GBIF Global Distribution
Key Habitat Requirements
Habitat: The juveniles and adults are primarily found in sandy or loamy upland Coastal Plain habitats. Pinelands and mixed pine-hardwoods are commonly used. Representative habitats include pine flatwoods, xeric pine-oak communities, dry prairies, pine rocklands, and xeric hammocks. Individuals are also occasionally found along the margins of dome swamps and hydric hammocks (Dodd 2013, Jensen et al. 2008, Krysko et al. 2019). A variety of disturbed habitats such as cut-over woods are also used.

The adults typically breed in fish-free seasonal habitats and rarely use permanent habitats. These can be as small as flooded vehicle tracks and small puddles in roadways to Carolina Bays. Representative habitats include roadside ditches, the flooded portions of agricultural fields, marshes, woodland pools, cypress savannas and ponds, Carolina Bays, limestone sinkhole ponds, and rainwater pools (Dodd 2013).

Populations in North Carolina are most often found in pine savannas, but also occur in landscapes with managed pine forests (Homyack et al. 2014, 2016, Johnson et al. 2016). They commonly breed in flooded depressions and seasonal ponds in pine flatwoods, as well as Carolina Bays, sphagnum bogs, roadside ditches, borrow pit ponds, and the flooded portions of agricultural fields.
Biotic Relationships: Predators in the wild are poorly documented. This species uses fish-free breeding sites and the larvae are presumably palatable to fishes and other aquatic predators. The juveniles and adults are undoubtedly taken by numerous predators such as aquatic snakes, turtles, mammals and birds, but documented cases are largely lacking. Meshaka and Layne (2015) reported one instance of predation by a ribbon snake in south Florida.
See also Habitat Account for Longleaf Pine Woodlands with Isolated Pools
Life History and Autecology
Breeding and Courtship: The breeding season is variable depending on the latitude, but this species is considered to be a winter or early spring breeder in most areas of the range outside of southern Florida. Breeding in southern Florida may occur at any time of the year and is often geared to seasonal rainfall patterns. Meshaka and Layne (2015), for example, noted that calling in the Everglades occurs throughout most of the year with a peak in June, while calling at the Archbold Biological Station in south-central Florida occurs from October to February with no discernible seasonal peak. At a nearby ranch where water levels are regulated, calling males can be heard year-round.

Calling elsewhere in the range can occur from October through April, although peak breeding normally occurs from late December through early April (Dodd 2013). Breeding can occasionally occur at other times of the year, particularly following exceptionally heavy rain events. Breeding may begin as early as October in northern Florida and southern Alabama, and normally occurs from December through April in Georgia (Dodd 2013, Jensen et al. 2008, Mount 1975). Breeding in North Carolina usually occurs from early February through early April.

Caldwell (1987) conducted detailed studies of the natural history of this species in South Carolina and found that the movement of males to a breeding site can begin as early as November. Most arrived within a month before the females began arriving in February. The adults will sometimes move during the day during overcast or rainy weather, but most move at night (Pechmann and Semlitsch 1986). Males and females that were marked by Caldwell (1987) remained in the pond for about the same amount of time and all left by late March or April. Operational sex ratio of the adults were around 1:1, and some females that left the pond during relatively dry years did not oviposit. The duration of stay in the pond varied markedly between years. The average stay for marked individuals in one year was 4.4 days for males and 4.9 days for females, compared to as long as 23.2 for males and 25.2 days for females in another year.

The males are secretive and usually call from hidden spots beneath clumps of grass or sedges or other vegetation while they are half submerged in shallow water (Dodd 2013). Very little is known about social communication and interactions when individuals are at the breeding sites. Egg laying presumably begins within a few hours after amplexus.
Reproductive Mode: Each female lays a series of small oval to oblong egg masses that are attached to support structures such as the blades and stems of grasses, sedges and rushes. The masses are of a loose consistency and typically about 25–30 mm in diameter (Dodd 2013). Egg masses in Georgia normally contain a few dozen to more than 100 eggs (Jensen et al. 2008). The freshly laid eggs are brown above and dull white to yellowish below and vary from around 0.5–1 mm in diameter. Each is surrounded by a single gelatinous envelope that is around 2.6–4.5 mm in diameter on average (Dodd 2013). Clutch sizes are poorly documented. Jensen et al. (2008) reported that females lay 500–1,500 eggs.
Aquatic Life History: The eggs normally hatch several days after being laid. Very little is known about the natural history of the larvae. Jensen et al. (2008) reported that the tadpoles in Georgia reach a maximum of 35 mm TL prior to metamorphosis, and that the larval stage lasts 6-8 weeks. Babbitt and Tanner (2000) estimated the larval period to last around two months in central Florida. Juvenile production at Caldwell's (1987) study site was very low (0-180 metamorphs per year), which indicates very high mortality for the pre-metamorphic stages. The peak in the emergence of the metamorphs was in May, with the froglets varying from 12–16 mm TL. At a site in southwestern Georgia Atkinson et al. (2021) trapped 3,216 metamorphs that were leaving a marsh over the course of nine breeding seasons.
Terrestrial Life History: The young metamorphs appear to only stay for a few weeks at most before dispersing away from the ponds to upland habitats (Caldwell 1987). Individuals move at night when conditions are cooler and more humid, and when sight-oriented predators are less active (Pechmann and Semlitsch 1986). The distances that the juveniles move from ponds is poorly documented, but Palis and Aresco (2007) trapped breeding adults that were leaving a pond as far as 200 m from the pond edge.

The juveniles and adults remain on land throughout most of the year. They hide beneath cover or may even burrow slightly into loamy or sandy soil during the day or during droughts (Carr 1940a). During favorable weather individals forage at night on small invertebrates (Dodd 2013). They tend to be active year-round in the southernmost populations (Meshaka and Layne 2015), and presumably for much of the year at more northern localities (Wright 1932). The diet is poorly documented, and the few specimens to date that were examined from Florida contained grasshopper nymphs, ants and beetles (Dodd 2013, Duellman and Schwartz 1958).

The young metamorphs at Caldwell’s (1987) study site in South Carolina grew rapidly and reached sexual maturity within 8-10 months. They bred the first winter or spring after metamorphosing. Life expectancy for this species is very low. Caldwell (1987) found that a majority of the adults perished at the breeding site, and that very few (generally < 3%) survived to breed a second time.
General Ecology
Population Ecology: Local populations are organized around local breeding sites and each typically consists of no more than perhaps a few hundred to a thousand or so adults. Semlitsch et al. (1996) monitored populations for 16 years in South Carolina where a total of 318 captured females produced only 237 metamorphs. Successful reproduction only occurred in three years -- and most in a single year -- which suggest that this site may largely function as an ecological sink. Other studies (Caldwell 1987, Cash 1994, Gibbons and Bennett 1974) that were summarized by Dodd (2013) suggest local populations of a few to several hundred adults are typically for sites in Georgia and South Carolina. Movements and connectivity between local populations are poorly documented, and it is uncertain to what extent populations exhibit metapopulation structure at different spatial scales.
Community Ecology: The Southern Chorus Frog often shares breeding ponds with many other amphibians (e.g., Atkinson et al. 2021), but community interactions between community members have not been examined.
Adverse Environmental Impacts
Habitat Fragmentation: Populations often exist in fragmented habitats so long as breeding sites are present and there is suitable habitat for the juveniles and adults. The extent to which deforestation and fragmentation is disrupting connectivity between local populations is unknown.
Status in North Carolina
NHP State Rank: S2
Global Rank: G5
Status in North Carolina: SC
Environmental Threats: The Southern Chorus Frog appears to do best in pine savannas where a cluster of seasonal ponds with varying hydroperiods are present. The destruction of natural habitats and urbanization are the greatest threats to this species.
Status Comments: Populations in North Carolina appear to have declined during the last few decades and this species is currently listed as S2 within the state. Most of our records are > 20 years old, and there are very few records for the last decade or so. The use of roadside ditches and other artificial habitats has helped to ameliorate the loss of many natural wetlands.
Stewardship: Populations appear to do best in fire-maintained pine savannas with clusters of seasonal wetlands embedded within the landscape.

Photo Gallery for Pseudacris nigrita - Southern Chorus Frog

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Recorded by: Rob Van Epps
Hoke Co.		Recorded by: Matthew Moskwik
Hoke Co.