Amphibians of North Carolina
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NC Records

Acris gryllus - Southern Cricket Frog


Taxonomy
Class: Amphibia Order: Anura Family: Hylidae Subfamily: Hylinae
Taxonomic Comments: Acris is a genus of small hylid frogs that is endemic to North America. Two species have traditionally been recognized, each with formally recognized subspecies. Acris gryllus is a southern form with two subspecies, while A. crepitans is a more northern and western form with three subspecies. After analyzing geographic variation in both nuclear and mitochondrial DNA, Gamble et al. (2008) retained A. gryllus as a valid species, but did not recognize subspecies due to discordance between their ranges and the geographic subgroups that were delineated by molecular data. Acris crepitans was split into two species. These are A. blanchardi, which was formerly considered to be a mid-western subspecies of A. crepitans (A. c. blanchardi), and A. crepitans (sensu stricto), which contains most other populations in the eastern US. Although very similar is general appearance, both A. gryllus and A. crepitans occur in North Carolina and are clearly distinct species based on DNA markers, morphology, vocalizations, and ecology (Gamble et al. 2008; Micancin 2008, Micancin and Mette 2009, Micancin et al. 2014, Nevo and Capranica 1985). The two species co-exist at several sites in the Fall-zone and Coastal Plain without any evidence of interbreeding.
Species Comments:
Identification
Description: Acris gryllus is a small frog that is very similar to A. crepitans and best identified by considering voice characteristics, range, and morphological features. The adults are small, slender frogs with a pointed snout. There are often two black lines or stripes on the posterior portion of the thigh, the lower being very thin and the upper much more prominent. The upper stripe is usually narrow and sharply defined, whereas the lower can appear as a thin line or simply be represented by vague stippling (Dodd 2013, Netting and Goin 1945). The webbing of the hind feet is moderately developed (Conant and Collins 1998) and generally extends less than half the distance of the longest toe. Two white anal tubercles are sometime evident between the back legs, but in many specimens may not be evident. The skin is noticeably rugose with small bumps and warts on the back, sides, and upper surfaces of the legs.

The dorsal ground color is highly variable and can be gray, tan, light brown, green, or olive (Dodd 2013). The most conspicuous mark is a diffuse, broad mid-dorsal stripe that is commonly gray, red, brownish red or green. It extends anteriorly from the urostyle, then forks just beyond the insertion of the front legs, with each branch leading towards an eye. A dark triangular mark that is of the same general ground color as the body is nested within the fork and points caudally. Beyond this -- and between the eyes and the snout -- is another area of light coloration that often matches the coloration of the mid-dorsal stripe. The sides of the body and dorsal surfaces of the legs are often overlain by several oblong darker blotches or bands. A relatively large and conspicuous blotch is usually present on the lower side between the front and hind legs. The undersides of the legs and body are white. Specimens in North Carolina and elsewhere in the range are sometimes rather uniformly colored above and often lack some or all of the Y-shaped patterning and triangular mark on the head. So, expect deviations from the general description above.

The male has a grayish-yellow to yellowish-brown vocal sac during the breeding season. At other times of the year it appears as a series of folds on the throat rather than a sac. The males are typically around 5-10% smaller than the females based on SUL, and the adults average around 20-23 mm SUL in most populations (Dodd 2013). Micancin and Mette (2009) reported an overall average of 21.1 mm SUL for specimens that they examined from North Carolina.

A. crepitans and A. gryllus both occur in North Carolina and are often difficult to distinguish from one another. In general, A. gryllus is slightly smaller and more slender, has a more pointed snout, longer legs, and less webbing between the toes (Conant and Collins 1998). It also has a more narrow and sharply defined black stripe on the thigh, and poorly developed anal tubercles (Beane et al. 2010, Dodd 2013).

Micancin and Mette (2009) analyzed museum specimens from North Carolina and found that the diameter of the anal tubercles and the extent of webbing on the fourth (longest) toe on the hind foot are the best morphological traits for distinguishing preserved specimens. At sites where these species occur syntopically in North Carolina, the texture of the skin, the appearance of the thigh stripes, and the degree of development of the anal tubercles are the most useful field traits other than call characteristics. The skin of A. crepitans is distinctly rugose with small warts and bumps on the back and legs, while that of A. gryllus is usually much smoother and looks translucent. The thigh stripes of A. crepitans are broader and have a more mottled appearance than A. gryllus, while those of A. gryllus are narrower, sharper-edged and less jagged.

If the males are calling, voice characteristics can be used to identify the species. Both species make clicking notes that resemble two small stones being tapped together. To the human ear, the advertisement call of A. crepitans consists of a series of somewhat raspy clicks. The intervals between clicks usually decrease with time and often end in a rapid, rattling sequence at the end. The clicks of A. gryllus are more metallic and crisper sounding. They also tend to accelerate with time but do not end in as rapid of a rattling sequence. We recommend making recordings in regions of the state where the two are sympatric and analyzing patterns using sound analysis software for positive identifications (see Micancin and Mette 2009). Details of call characteristics are presented below and in the A. crepitans account.

In addition to morphological traits and vocalizations, specimens in North Carolina can often be assigned to species based on geographic locality. Populations in the northern half of the Fall Zone, almost all of the northern half of the upper Coastal Plain, and the western Piedmont and mountain valleys are all assignable to A. crepitans (Micancin 2008, Micancin and Mette 2009, Micancin et al. 2012). Populations in some areas of the lower Coastal Plain and the Sandhills region could be either species and need additional evidence such as voice or morphological characteristics to assign to species. Acris gryllus was previously present in the northern half of the Fall Zone and the northern half of the upper Coastal Plain, but now appears to be absent from almost all of this general region based on field surveys (see Micancin 2008, Micancin and Mette 2009, and Micancin et al. 2012 for distribution maps).

The tadpoles appear to be largely indistinguishable from those of A. crepitans except for the free part of the spiracle’s tube being longer in A. gryllus than in A. crepitans (best viewed in preserved specimens). The tadpoles of both are medium-sized, with grayish to greenish bodies above. They have long tails with low tail fins that are lightly mottled with tan and scattered black flecks. Many tadpoles have conspicuous black tail tips, although some tadpoles lack these. There is a light stripe bordered by dark stripes along the side of the snout, and the throat is light with a dark band extending across the chest (Dodd 2013). Large tadpoles range from 30-46 mm TL but are usually around 25 mm. The mature tadpoles are markedly larger than the froglets that emerge at metamorphosis.
Vocalizations: The songs of both of our species of cricket frogs consist of a series of clicks, often described as "gick" "gick" "gick" and likened to pebbles, marbles, or ball-bearings being struck together. There are some differences that are detectable in the overall pattern of these clicks, but the clearest diagnostic difference can be seen in the structure of the individual clicks. As shown by Blair (1958), Nevo and Capranica (1985), and Micancin (2008), the clicks of both species actually consist of a series of pulses rather than a true click (a vertical bar on a spectrogram or oscillogram). In Acris gryllus, these pulses are arranged in a tight sequence with a decline in amplitude from beginning to end; in A. crepitans, the pulses are often longer in duration and divided into two or more well-spaced groups that are usually uniform in amplitude (see Figure 1.2 in Micancin, 2008). In the recording shown below, a typical sequence of a single calling male is shown first, followed by a slowed-down version of three clicks, also magnified by stretching out the time on the x axis (play the recording to see both). The oscillogram (amplitude) plot shows the pulses particularly well that compose each individual click, including the decline in amplitude within each pulse that is characteristic of Acris gryllus.
Technical Reference: Dodd (2013)
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AmphibiaWeb Account
Distribution in North Carolina
Distribution Comments: Acris gryllus is largely restricted to the southeastern Coastal Plain, with the range extending from southeastern Virginia through all of Florida, then westward to southeastern Louisiana. In Georgia and Alabama, the range extends outside of the Coastal Plain into extreme western Georgia and central and northwestern Alabama, with the northern limit ending in southwestern Tennessee. Populations in other areas may extend slightly into the Piedmont along river floodplains.

In North Carolina, this species is essentially restricted to the Coastal Plain, including offshore islands on the Outer Banks (e.g., Braswell 1988, Gaul and Mitchell 2007). Populations appear to have been extirpated from much of the northern portion of the upper Coastal Plain, and are now largely restricted to the southern half of the Costal Plain and coastal areas of the northern Coastal Plain.
County Map: Clicking on a county returns the records for the species in that county.
Key Habitat Requirements
Habitat: Acris gryllus it typically found in the vicinity of permanent or temporary wetlands such as wet prairies, seepage bogs, sloughs, canals, sawgrass prairies, grassy meadows, Carolina bays, farm ponds, small lakes, swamps, and flooded ditches. The surrounding habitats tend to be mesic to xeric sites such as longleaf pine-turkey oak sandhills, mixed pine-oak woodlands, hardwood forests, mesic and xeric hammocks, pine flatwoods, as well as agricultural fields and silvicultural operations (Dodd 2013). During the breeding season the adults frequent the shorelines of wetlands, especially where there is an abundance of low-growing emergent grasses or sedges or floating mats of vegetation.

In North Carolina this species is essentially restricted to the Coastal Plain where it is associated with acidic wetlands of several types. These include streamhead pocosins and swamp forests, the marshy shorelines of Carolina Bays, depression ponds, and beaver ponds. A variety of constructed wetlands are also commonly used such as borrow pits, farm ponds, small lakes and reservoirs. Most of the natural habitats have a substantial amounts of sphagnum, but sandy, peaty, or mucky substrates are all used. Even though the larvae appears to lack chemical defenses against predatory fishes (Kats et al. 1988), this species is commonly found in fish-filled habitats such as farm ponds and reservoirs. The larvae likely survive by exploiting vegetated shallows that have few fish. Terrestrial habitats that are used by the adults include both frequently burned savannas and flatwoods, as well as rarely burned bottomlands and swamps. Within its range, virtually any type of permanent to semi-permanent waters can support populations of this species.
Environmental and Physiological Tolerances: Acris gryllus seems to tolerate acidic conditions much better than A. crepitans (Mecham 1964).
Adaptations to Natural Disturbances: Like many anurans that occur in the Coastal Plain, this species seems to be well adapted to surviving periodic natural disturbances such as those from wildfires or severe storms. Gunzburger et al. (2010) found that populations recover quickly in coastal areas that receive overwash from hurricanes, and prescribed burning may actually enhance populations by keeping habitats open (Dodd 2013).
Biotic Relationships: The larvae frequently coexist with odonates, predatory fishes, newts and other aquatic predators. They lack chemical defenses against fish, and appear to be palatable to aquatic predators in general (Kats et al. 1988). Their primary defense against odonates, fishes and newts is to reduce their activity level and encounter rates with predators (Richardson 2001). Turnipseed and Altig (1975) noted that the larvae mostly used vegetated shallows where fish were largely excluded.

The larvae often have black tail tips that likely direct attacks from odonates away from the head and body (Dodd 2013). Studies of A. blanchardi -- which is a closely related species whose larvae also have black tail tips -- suggest that the presence of fish may trigger a reduction in size of the black tip in developing larvae (Caldwell 1982, Carfagno et al. 2011). This likely makes the tadpoles less conspicuous to fish predators.

Acris gryllus is an excellent jumper and an individual will frequently flee an approaching predator or human by making zig-zagging leaps, jumping into the water, and swimming rapidly among vegetation. The juveniles and adults likely are preyed upon by a variety of aquatic and semi-aquatic predators such has fishing spiders, ranid frogs, snakes, wading birds, grackles and mammals (Dodd 2013). Fogarty and Hetrick (1973) found 231 adults in 410 Cattle Egrets that they examined from Florida.
See also Habitat Account for General Blackwater Shorelines
Life History and Autecology
Breeding and Courtship: The adults set up small home ranges along shorelines and tend to be sedentary during the breeding season. Studied by Bayless (1966) in Louisiana show that individuals rarely move more than a few meters from their previous point of capture.

During the breeding season the males call from land along the shoreline, typically within one meter of the water. Forester and Daniel (1986) studied a small population in a flooded sand pit in Georgia and found that individual males moved an average of only 52 cm between consecutive nights. They appeared to be territorial based on the fact that each held a non-overlapping territory, with the mean size being only 0.56 m2. Direct aggressive encounters were not observed, and the size of the territory was not correlated with either the number of nights a male was present or with mating success. The authors observed three cases where females approached calling males, with the pairs later amplexing. One approaching female repeatedly moved in a tight circle around a male with occasional head-cocking in an apparent attempt to locate the male. The males eventually approached the females and amplexed them.

Mohr and Dorcas (1999) and Bridges and Dorcas (2000) monitored calling at ponds in South Carolina and found that individuals called throughout the day and night, and on every day of monitoring. Daytime calling was typically lowest in the morning with a gradual increase throughout the day and into the evening. Frogs called most during the evening hours. Calling can occur year-round in certain populations in Florida and during much of the year elsewhere (Dodd 2013). Males in Georgia call from February to October (Jensen et al. 2008), while those in North Carolina call from late March or early April through August (Alexander 1966). Mating typically takes place from late spring throughout the summer, so the reason that males continue to call well after the breeding season has ended has yet to be determined.

Mating and egg laying in most populations occurs during the late spring and early to mid-summer. Bayless (1966) only observed amplexed pairs in March and April in Louisiana, while breeding in Georgia occurs from April to June (Jensen et al. 2008). Based on the presence of larvae in ponds (e.g., Babbitt and Tanner 2000), Dodd (2013) believed that at least some breeding occurs nearly year-round in certain areas of Florida. Turnipseed and Altig (1975) found that females only bred during rain events in a pond in Mississippi.
Reproductive Mode: Once amplexed, the female moves to water and the eggs are fertilized as they are laid singly or in small groups of three to four. The eggs sometimes stick together to form a loose mass of seven to ten eggs (Dodd 2013). The eggs either rest freely on the substrate or cling to vegetation and debris in the ponds. The freshly laid eggs are dark brown to buffy olive above and cream to white below. The ovum averages about 1.2 mm in diameter, and is surrounded by one or more gelatinous membranes ((Brown 1956, Dodd 2013). The clutch size is poorly documented. Wright (1932) reported a single value of 241 eggs, while Alexander (1966) reported from 99-156 eggs per clutch in North Carolina specimens. The embryos typically hatch within four days after egg deposition (Dodd 2013).
Aquatic Life History: Very little is known about the larval ecology of this species. The larval period lasts around 1-3 months, and the metamorphs are typically 9–15 mm SUL (Bayless 1966, Dodd 2013, Jensen et al. 2008, Wright 1932).
Terrestrial Life History: The Southern Cricket Frog has a strong affinity for wetlands and can be found during most months of the year around the margins of hydric sites. The adults commonly inhabit the terrestrial edges of wetlands, as well as vegetated shallows and floating vegetation mats. During the non-breeding season, they often move away from the breeding sites to hydric sites such as the margins of cypress swamps, streams and seepages, or into wet prairies, roadside ditches and other moist sites (Dodd 2013). Several researchers have found them hundreds of meters from the nearest breeding site. For example, Dodd (1996) captured them from 255 to 492 m (mean = 383 m) from the nearest water in sandhills habitat in Florida, while Micancin (2010) found a single female in North Carolina 562 m from the nearest breeding site.

During the breeding season the adults set up small territories along shorelines and tend to be sedentary. Occasionally individuals do move longer distances over the course of the activity season (Dodd 2013). The greatest movement that was documented by Bayless (1966) was around 65 m over a 6 month period. Frogs that are experimentally displaced 100 or more meters from their home ponds successfully returned (Ferguson 1963), which suggests that individuals that move away from ponds after the breeding season can return to familiar habitats on land. Individuals are active year-round except during exceptionally cold bouts of weather. This species is generally active year-round in North Carolina except perhaps in January through mid-February.

The juveniles and adults feed on a variety of small invertebrates. Dodd (2013) summarized the results of dietary studies and noted that ants appear to be a very important prey group, as they are for many small frogs. Studies from Florida and Louisiana suggest that A. gryllus is an opportunistic generalist that takes a wide range of prey (Bayless 1969b, Beck 1948, Carr 1940a, Franz 1972). In addition to ants, some of the known prey include collembolans, mayflies, flies and fly larvae, beetles, leaf bugs, true bugs, aphids, termites, mosquitoes, spiders, mites, and a variety of miscellaneous larval and adult insects. Franz (1972) did not find any prey in frogs that were collected during the night, which suggests that individuals only feed during the day.
General Ecology
Population Ecology: Local populations often consist of a few hundred to many hundreds of individuals, particularly along small lakes or other large wetlands (Dodd 2013). Wright (1932) considered this species to be the most abundant frog in the Okefenokee Swamp, and Dodd (2013) described it as one of the most abundant frogs around ponds and lakes in north-central Florida. The adults tend to space out around the margins of breeding ponds, which suggests that they may be territorial. Turner (1960) found that individuals were spaced at intervals ranging from 1.7 to 1.9 m from their nearest neighbor in and around a grassy wetland in Louisiana. The adults appear to be short-lived and probably only rarely survive more than three years. Some authors have reported that the adults are able to breed the year following metamorphosis (e.g., Jensen et al., 2008), but Alexander (1966) found that 50-70% of females in North Carolina required an additional year to mature.
Community Ecology: This species frequently shares breeding ponds with other anurans, but little is known about competitive interactions among community members. A. gryllus and A. crepitans overlap geographically in some areas of their ranges, but tend to have difference habitat preferences where they occur sympatrically (Dodd 2013). Where they do share a pond, Bayless (1966, 1969b) found that individuals show evidence of microspatial segregation to some extent. The extent to which these species compete where they share ponds needs additional study. Mecham (1964) found these two species to commonly share breeding sites in Alabama.
Adverse Environmental Impacts
Status in North Carolina
NHP State Rank: S5
Global Rank: G5
Environmental Threats: The Southern Cricket Frog does not show any evidence of marked declines throughout its range except in the northern sections of the upper Coastal Plain of North Carolina where populations have disappeared (Micancin and Mette, 2009). Many local populations have been impacted due to the loss or degradation of wetlands throughout the South. Surdick (2005) found decreased abundance relative to natural reference sites on lands affected by silviculture, agriculture, and urbanization. In general, this species seems to tolerate timbering and urbanization reasonably well (reviewed by Dodd 2013). Prescribed burning may actually enhance populations by keeping habitats open (Dodd 2013).
Status Comments: Although long considered common and abundant in the North Carolina, declines have recently been detected in the northern half of the upper Coastal Plain, with populations apparently no longer present in in the Neuse, Tar-Pamlico, and Roanoke basins, where numerous museum records exist for this species from prior to 1990 (Micancin 2008, Micancin and Mette 2009, Micancin et al. 2012). While the populations in the southern half of the Coastal Plain may still be secure, not enough is known about the causes for their decline in the northern half. Instead of their current State Rank of S5 -- indicating complete security from extirpation -- we recommend listing this species as S4S5 instead, indicating at least some uncertainty about its status in the state.

Photo Gallery for Acris gryllus - Southern Cricket Frog

8 photos are shown.

Recorded by: Jim Petranka and Becky Elkin
Brunswick Co.
Recorded by: Steve Hall and Bo Sullivan
Richmond Co.
Comment: This graph shows details of three clicks. Note how each is composed of a tight sequence of pulses that decline in amplitude from beginning to end.
Recorded by: Steve Hall and Bo Sullivan
Scotland Co.
Recorded by: Steve Hall and Bo Sullivan
Scotland Co.
Recorded by: Steve Hall
Scotland Co.
Recorded by: Morgan Freese
Dare Co.
Recorded by: Mark Shields
Carteret Co.
Recorded by: Mark Shields
Onslow Co.