Amphibians of North Carolina
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NC Records

Pseudacris brimleyi - Brimley's Chorus Frog

Taxonomy
Class: Amphibia Order: Anura Family: Hylidae Subfamily: Hylinae
Taxonomic Comments:
Species Comments:
Identification
Description: The adults are small frogs that are usually tan or light brown with three dark stripes on the dorsum that narrow towards the head. The most prominent feature is a bold dark brown or blackish stripe that runs from the snout through the eye to the groin. The ground color can vary from yellowish to reddish brown or dark brown. The three dorsal stripes may be obscure on certain individuals, and the lateral stripes are often the most prominent (Beane et al. 2010, Dodd 2013, Jensen et al. 2008). The skin is smooth, and a light line is present on the upper jaw that extends to the shoulder. The back leg has a distinctive dark line along the outer edge of the shank. The back leg may also have one or more elongated blotches that run parallel to the limb axis, rather than transverse as is the case in other Pseudacris species. The venter is white to yellowish white and the chest has varying amounts of small dark spotting that may be missing on some individuals. The males have a dark vocal sac during the breeding season and average slightly smaller than the females. Wright and Wright (1949) list size ranges of 24–28 mm SUL for males and 27–35 mm SUL for females. In North Carolina some specimens resemble the Coastal Plain form of P. feriarum and are best distinguished by the dark line along the outer edge of the shank (missing on P. feriarum).

The larvae have brown to greenish brown bodies that may have scattered gold or yellowish flecks. The chin and throat are darkly pigmented (usually with spots) and the tail musculature is sharply bicolored or striped, with the white ventral portion of the tail coloration about 50% of the basal muscle height. A dorsal light stripe extends forward through the eye to near the snout and the tail fins are sparsely speckled (Dodd 2013). The tadpoles obtain a maximum size of around 30 mm TL.
Vocalizations: The advertisement call is a short, repetitive, rasping trill (“kr-r-r-a-k” - “kr-r-r-a-k” - “kr-r-r-a-k”...) and males may call both during the day and at night. The call rate is temperature-dependent, with each call commonly lasting about one-half of a second and repeated about once every second or so.
Technical Reference: Dodd (2013)
Online Photos:    Google   iNaturalist
Observation Methods: The adults appear to be secretive during the day and are best observed when calling at the breeding sites.

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AmphibiaWeb Account
Distribution in North Carolina
Distribution Comments: Brimley’s Chorus Frog is found throughout the Atlantic Coastal Plain from Spotsylvania County and vicinity in eastern Virginia southward to the extreme northeastern Coastal Plain in Georgia. In North Carolina, populations have been found throughout most of the Coastal Plain with the exception of the Fall Line region where it appears to be absent or rare. This species is present on Roanoke Island (Gaul and Mitchell 2007), but generally appears to be absent from most coastal islands.
Distribution Reference: Beane et al. (2010), Dodd (2013)
County Map: Clicking on a county returns the records for the species in that county.
GBIF Global Distribution
Key Habitat Requirements
Habitat: Brimley’s Chorus Frog is mostly found in bottomland hardwood forests where it is commonly associated with swampy habitats in or near rivers and streams. Breeding occurs in shallow temporary or semipermanent pools in floodplains and wet woods (Beane et al. 2010, Dodd 2013). With the conversion of many bottomland forests to agricultural and silvicultural lands, populations have responded by using open habitats that are usually near bottomland forests. These include flooded roadside ditches, shallow seasonal pools and ditches in cutover areas, and the shallow portions of flooded agricultural fields.

In North Carolina, populations frequent bottomland forests and swamps where they breed in shallow, fish-free seasonal and semi-permanent pools such as the edges of flooded red maple swamps. They also use sunny or partially shaded sites, including flooded roadside ditches, shallow areas in flooded fields, and seasonal pools in managed forests (Brandt 1936; Beane et al. 2010, Gosner and Black 1958, Johnson et al. 2016 a, b). Breeding sites are usually near woods, but Gosner and Black (1958) found one that was an estimated 800 m away from the nearest forest habitat.

Johnson et al. (2016 a, b) examined breeding site use in a managed pine landscape in coastal North Carolina. They found that the adults were less likely to use roadside ditches that usually contained fish compared with seasonal and semipermanent ponds in forested sites that were less likely to have fish. Breeding occurred in both unmanaged forests where hardwoods were well represented, and in managed Loblolly Pine stands. Ponds in pine stands were less shaded and contained more grassy growth, and were used only slightly less based on occupancy probabilities than those in unaltered habitats. Larvae were not recovered from ditches when dipnetting, but were found in pond sites.
Biotic Relationships: Very little is known about larval adaptations to predators. Jensen et al. (2008) reported that the larvae are eaten by Ambystoma larvae, newts, fishing spiders, dragonfly larvae, predaceous beetles, fish, and birds, while Dodd (2013) also listed the Eastern Garter Snakes (Thamnophis sirtalis) and watersnakes (Nerodia sp.) as known predators. The fact that this species mostly breeds in fish-free habitats implies that the larvae are either highly vulnerable to fish predation, or that females actively avoid fish pools when choosing oviposition sites. The ground coloration and patterning of the adults is cryptic and undoubtedly make them difficult to distinguish when resting on the forest floor.
See also Habitat Account for Coastal Plain Wet-Hydric Forests
Life History and Autecology
Breeding and Courtship: Brimley's Chorus Frog tends to be active during the winter months except during cold spells. Calling males have been heard as early as mid-January in North Carolina, and amplexed pairs and eggs have been observed from mid-February through mid-April (Brandt 1936, Brandt and Walker 1933, Gaul and Mitchell 2007). In Virginia, Mitchell (1986) heard calling males from 7 March–22 April and observed egg laying from 10 March–22 April. At another site the males called from 23 February-7 April (Mitchell 1996).

Most aspects of social behavior are poorly documented. The males have been observed calling from the bases of grass clumps, while sitting on sphagnum mats (Mitchell 1996), or while in the water. They stake out calling territories and will drive off rival male intruders (Dodd 2013, Mitchell 1986). Amplexus is supra-axillary and egg laying presumably begins within a few hours after the adults amplex.
Reproductive Mode: Each female lays several small, loose, egg masses that are attached to vegetation and woody debris just below the water’s surface. The freshly laid eggs are dark brown to black above and white below, and are surrounded by a single jelly envelope. Eggs from two clutches that were examined by Gosner and Black (1958) were 1.3 to 1.71 mm in diameter (mean = 1.45), with envelopes that varied from 6.75 to 8.64 mm in diameter (mean = 7.5 mm). Eggs that were kept in the lab hatched in 4.5–5.5 days, but development presumably takes longer in natural habitats. Jensen et al. (2008) reported that development to hatching requires 1-2 weeks in Georgia populations. Clutch sizes are poorly documented. Gosner and Black (1958) noted that two captive females laid 264 and 290 eggs, while Mitchell and Pague (2014) reported that five females from Virginia laid from 170-324 eggs (mean = 245).
Aquatic Life History: Very little is known about the life history of the larvae. Hatchlings that were grown in the lab by Gosner and Black (1958) metamorphosed in 35–60 days and the metamorphosed froglets were 9–11 mm SUL. We have no data from natural populations.
Terrestrial Life History: Most aspects of the terrestrial life history are poorly documented. The metamorphs presumably leave the ponds and disperse into the surrounding fields and swampy woodlands surrounding breeding sites. Dodd (2013) noted that they hide under woody debris, leaf litter, and downed logs during the day and emerge at night to feed. Sexual maturity is probably attained by the first spring after metamorphosis, but little else is known about the terrestrial stages (Dodd 2013).
General Ecology
Population Ecology: We have very little information on the population biology or most other aspects of the natural history of this species. Local populations are thought to be small because many of the breeding sites are also small. Mitchell (1996) estimated that there were 25-35 males calling at one site in Virginia, which suggests a population of perhaps 100-200 adults or less.
Adverse Environmental Impacts
Habitat Loss: The widespread timbering of bottomland forests and replacement with agricultural and urban lands, along with the destruction of wetlands in the Atlantic Coastal Plain, have undoubtedly eliminated many populations since European colonization.
Habitat Fragmentation: We know so little about the natural history of this species that it is difficult to assess the impact of landscape fragmentation. Wet bottomland forests appear to be critical habitats for the adults, particularly outside of the breeding season. Johnson et al. (2016 a, b) found that the adults often breed in seasonal and semipermanent ponds in managed pine forests, which suggests that populations can tolerate some level of disturbance so long as suitable breeding sites are present.
Status in North Carolina
NHP State Rank: S4
Global Rank: G5
Status in North Carolina: W5
Environmental Threats: The loss of bottomland forests and the continued degradation and destruction of seasonal and semipermanent wetlands in the Coastal Plain are of greatest concern.
Status Comments: Brimley’s Chorus Frog appears to have declined in some areas of its range. In North Carolina, it status within the entire Coastal Plain needs to be assessed. We have numerous historical records, but relatively few records after 2000 except in some areas of the lower Coastal Plain where populations appear to be stable.

Stewardship: Populations are best maintained by having a cluster of seasonal or semipermanent, fish-free ponds that are either embedded within or near bottomland forests. This species also uses ditches and seasonal ponds in cut-over areas that can serve as substitutes for natural habitats.

Recording Gallery for Pseudacris brimleyi - Brimley's Chorus Frog

2022-02-17. Beaufort Co. Jim Petranka and Becky Elkin - 5-6 calling from swamp and opening immediately next to swamp.

2022-02-17. Washington Co. Jim Petranka and Becky Elkin - Several calling from area with Phragmites (?) - tall, robust aquatic.

2022-02-17. Beaufort Co. Jim Petranka and Becky Elkin - Only two adults were heard calling from a shallow roadside ditch.

2022-02-17. Hyde Co. Jim Petranka and Becky Elkin - A chorus of 15-20 or so were calling from a pocosin; 11:40 AM; air temp = 70F.

Photo Gallery for Pseudacris brimleyi - Brimley's Chorus Frog

4 photos are shown.

Recorded by: Jim Petranka and Becky Elkin
Beaufort Co.		Recorded by: Jim Petranka and Becky Elkin
Beaufort Co.
Recorded by: Jim Petranka and Becky Elkin
Hyde Co.		Recorded by: Robby Deans
Beaufort Co.