Taxonomy
Class: AmphibiaOrder: AnuraFamily: HylidaeSubfamily: 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. 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). 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. 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. 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). 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)Online Photos: Google iNaturalist
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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. County Map: Clicking on a county returns the records for the species in that county.
GBIF Global Distribution
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. 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. 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.
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. 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. 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: S5Global Rank: G5Environmental 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 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.
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