Amphibians of North Carolina

Scientific Name:	Common Name:		Family (Alpha):

NC Records
Bufonidae Members:
Anaxyrus terrestris - Southern Toad

Taxonomy

Class: Amphibia

Order: Anura

Family: Bufonidae

Synonym: Bufo terrestris


Taxonomic Comments: The Southern Toad occasionally hybridizes with several other species of toads, including Fowler's Toad and the American Toad. This typically happens when a male amplexes a female of an opposing species where the two share a breeding site (Dodd 2013). Volpe (1959) documented what appeared to be extensive hybridization between A. terrestris and A. fowleri in southeastern Louisiana and Mississippi, but hybridization appears to be less common elsewhere. In North Carolina hybridization appears to happen on occasion with both Fowler's Toad and the American Toad (Beane et al. 2010, Gaul and Mitchell 2007, Wilbur et al. 1978). Barrow et al. (2018) analyzed mtDNA variation in populations in the Southeast and found six mtDNA clades that did not correspond with geography. Their analyses of nuclear genes resulted in poorly resolved gene trees.
Species Comments:

Identification

Description: Anaxyrus terrestris is a medium-sized toad with most adults varying from 41-92 mm SUL. The dorsal ground color is usually medium brown, but can vary from reddish to olive green, gray, or nearly black (Dodd 2013). The dorsal patterning is also variable, with some individuals being rather uniformly colored and others mottled with varying shades of cream, blackish and earth tone colors or blotches. Individuals sometimes have a rather poorly developed complete or partial light mid-dorsal stripe that extends from near the snout to the urostyle. The skin is covered with small circular bumps and larger warts, and there is a prominent oblong parotoid gland behind each eye. The dorsal and dorsolateral regions often have a series of small blackish spots that typically have one, or less commonly two, large warts per spot. The venter is dull white to light gray with scattered dark spots on the chest. Males normally have a dark subgular vocal sac. The vocal sac is not always darkly colored, particularly outside of the breeding season. The most distinguishing feature of this species is the pair of well-developed cranial crests. Each one projects backwards between the eyes and has a prominent, large knob at the end. From there, a postorbital (transverse) ridge extends laterally to the parotoid gland, where it is connected by a backward projecting spur. These features become more prominent with age and are best developed in the adult females (Beane et al. 2010, Dodd 2013). Males are usually 42-82 mm SUL and females 44-92 mm SUL (Wright 1949), but much larger specimens are often encountered on islands along the coasts of Georgia, Florida, and South Carolina. Jensen et al. (2008) listed a range of 41-75 mm for most specimens in Georgia, with island specimens sometimes attaining 113 mm SUL. Beane et al. (2010) reported a range of 44-98 mm for species in the Carolinas and Virginia. Males at any given site are commonly 10-20% smaller than the females. The larvae are small and black and often have small purplish dots present dorsally. The venter is also blackish with somewhat purplish, scattered spots (Dodd 2013). The upper tail fin is faintly spotted, but the lower tail fin is not. The tail fins are about equal in depth and wider than the tail musculature. The eyes are positioned close together dorsally and there is a light oblique mark behind each eye. Tadpoles can reach maximum total lengths of around 24–28 mm before transforming, but most are usually much smaller. In North Carolina, the Southern Toad is best separated from the American Toad and Fowler's Toad by the prominent large knobs at the end of the interorbital crests and the number of warts in the largest dorsal blotches. This species is largely geographically separated from the American Toad, which is associated with more mesic habitats in the Piedmont and Blue Ridge. Fowler’s Toad lacks the prominent knobs on the interorbital crests, has three or more small warts in each dark dorsal blotch, has a single spot in the middle of the chest, and usually has a well developed light mid-dorsal stripe.
Vocalizations: The male's advertisement call is a loud and melodic trill that typically lasts for 4-9 seconds. It is then repeated after a short pause. The call resembling that of the American Toad but is shorter in duration and slightly higher pitched. If accidentally amplexed by another male, a male will utter a chirp-like release call and vibrate his body, which serves to warn males that the amplexed animal is not a female.
Technical Reference: Dodd (2013)
Online Photos: Google iNaturalist
Observation Methods: Individuals are commonly found on roads at night during rainy weather and can be heard calling from the breeding sites.

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AmphibiaWeb Account

Distribution in North Carolina

Distribution Comments: The Southern Toad is mostly restricted to the southeastern Coastal Plain. The range extends from southeastern Virginia southward through the Carolinas and Georgia to extreme southern Florida, including the Florida Keys. It extends westward through east-central and southern Mississippi to southeastern Louisiana. Dodd (2013) reported that an isolate occurs in the upper Piedmont on the border of Georgia and South Carolina, but Jensen et al. (2008) do not mention this in their treatment of this species in Georgia. Populations are also found on various Atlantic and Gulf Coast barrier islands, including at several sites on the Outer Banks (Gaul and Mitchell 2007, Lewis 1946). In North Carolina populations occur mostly in the Coastal Plain, with a few records from the extreme eastern Piedmont.
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: The juveniles and adults can be found in a wide range of terrestrial habitats so long as suitable breeding sites are nearby. They are commonly found in sandy habitats where they can escape physiologically stressful surface conditions by burrowing beneath ground using the spade-like cornifications on their hind feet. However, they also use a variety of hydric sites. Dodd's (2013) comprehensive list of habitats that are used throughout the range includes seashore scrub, seashore dunes, pine flatwoods, sandhills, xeric hammocks, dome swamps, hydric hammocks, forested wetlands, steephead ravines, wet prairies, upland hardwood forests, and mixed-upland forests. They also occur in urban and agricultural landscapes.

In North Carolina, the juveniles and adults occur in numerous habitats including pinelands and mixed pine-hardwood forests, barrier islands with both maritime scrub and maritime forests, the edges of agricultural fields, residential neighborhoods, and forests that are managed for wood products. Populations are relatively common in the Sandhills and in the eastern Coastal Plain where sandy soils prevail. This species tolerates burning well, and may increase the year following a prescribed burn (Greenberg et al. 2019).

The breeding sites vary from small seasonal pools and puddles to large lakes. The larvae have chemical defenses that provide limited protection against fishes and other aquatic predators (Lefcort 1998), and often breed in vegetated shallows in permanent habitats with fishes. Examples of the habitats that are used include flooded tire ruts and puddles in roads, flooded ditches, farm and golf course ponds, borrow pits, marshes, flooded agricultural fields, Carolina bays, cypress and gum ponds, cypress savannas, and water features in urban and suburban settings. They will also breed in the quiet waters of shallow coastal plain streams (Dodd 2013).

Populations in North Carolina use both seasonal and permanent habitats, with the latter often having fishes. The breeding sites include natural seasonal depressions, floodplain backwater pools, pocosins, swamps, freshwater marshes, flooded pastures, farm ponds, roadside ditches, and flooded borrow pits.

Biotic Relationships: The larvae have chemical defenses against fishes and are usually rejected when presented to sunfishes (Lefcort 1998). Nonetheless, they are preyed upon by numerous aquatic predators such as dragonfly larvae, giant water bugs, newts, sirens, and amphiumas (Babbitt and Jordan 1996, Lefcort 1998, Wilbur et al. 1983). Richardson (2001) found that larvae do not reduce their activity level in the presence of dragonfly naiads, newts, and sunfish, which suggests that they rely on chemical defenses and the formation of aggregates and schools to minimize predation risks. Lefcort (1998) found that tadpoles reduced their movements after detecting chemical cues from a sunfish, but showed no response to unfed Two-toed Amphiumas and Lesser Sirens. When tested against amphiumas and sirens that were fed toad tadpoles, they exhibited fleeing behavior. Individuals were also able to differentiate between sirens and amphiumas that were fed toad versus leopard frog tadpoles, and were also less likely to decrease movements when in relatively large groups.

The juveniles and adults produce toxic skin secretions that are concentrated in the parotoid glands and warts. If approached by a predator, they may flee or become immobile. They may also crouch with the chin tucked downward or inflate the body with air and rear up on their hind legs (Dodd 2013). This posturing orients the glands toward the predator and make the toad more difficult to attack or handle. Some of the known predators include the Eastern Hog-Nosed Snake (Heterodon platirhinos), North American Racer (Coluber constrictor), Eastern Indigo Snake (Drymarchon couperi), gartersnakes (Thamnophis) and watersnakes (Nerodia). Fogarty and Hetrick (1973) found 20 adults and 149 juveniles in 410 Cattle Egrets that were examined from north-central Florida. Spiders are also known to feed on the young (Nyffeler and Altig 2020).

See also Habitat Account for Coastal Plain Mixed Habitats

Life History and Autecology

Breeding and Courtship: The seasonal time of breeding varies geographically, but normally occurs from late winter or early spring into the summer months. Populations in southern Florida can breed year-round, while those in northern Florida begin in February and breed sporadically through September or the end of October (Greenberg et al. 2017, Krysko et al. 2019). Other reports include breeding in Louisiana from February through August (Dundee and Rossman 1989), and breeding in Alabama from March to September (Brown 1956). Semlitsch et al. (1996) found that populations in South Carolina can breed in all months of the year at their study site. Brimley (1944) reported that the adults breed from March through June in North Carolina, while Beane et al. (2010) noted that breeding mostly occurs from late-February through May in the Carolinas and Virginia, with occasional breeding before or after this time span. In general, most populations appear to have a peak in breeding in late-winter or early spring through late-spring or early summer. Opportunistically breeding bouts can occur at times outside of the peak season that are usually triggered by very heavy rain events (Dodd 2013). Movements to the breeding sites occur mostly at night, particularly during rainy weather (Todd and Winne 2006).

The males call from either the shoreline or from nearby shallow water to attract females. Males prefer open locations for calling, and generally avoid microhabitats with obstructing vegetation such as thick cattail stands. Rainfall is not necessary to initiate calling, but heavy rains often stimulate large numbers of males to call, particularly at times of the year that are past the peak in seasonal breeding. Females move towards the calling males, but may be intercepted and amplexed by satellite males or other males that they encounter along the way (Dodd 2013). Amplexus can be either axillary or supra-axillary depending on the size of the female. Once amplexed, the female typically select a site in shallow water to lay her eggs.

Reproductive Mode: Each female lays either one or two long, continuous gelatinous strings of eggs. The eggs are blackish above and grayish-white below, and are surrounded by two jelly envelopes (Dodd 2013). They are encased within a singular tubular membrane that is often weakly coiled, and there are typically 2-3 eggs per cm of tube length in freshly laid clutches. Females either deposit their eggs loosely on the bottoms of shallow pools or coil them around aquatic plants, decaying vegetation, and other support structures. When breeding in lakes or other sites that are relatively deep, the eggs are typically deposited on support structures such as aquatic vegetation mats near the pond surface (Dodd 2013).

Each female produces several thousand eggs and clutch size is positively correlated with female SVL. Metts et al. (2013) reported average clutches of 4,060 (N = 15) and 3,939 (N = 29) eggs for two populations in South Carolina, while Wright (1932) counted 2,888 eggs from one female. The embryos normally hatch within 2-4 days after egg deposition (Dodd 2013).

Aquatic Life History: The tadpoles feed in vegetated shallows and often move about in schools in shallow water. The diet is poorly documented, but is presumably similar to that of other toads, with the tadpoles filter-feed on detritus, algae, and other food that is suspended in the water column, and eating filamentous algae, blue-green algae, periphyton, diatoms and the soft tissues of decaying plants (Dodd 2013). The tadpoles will opportunistically feed on the eggs of anurans (Babbitt 1995, Punzo and Linstrom 2001) and likely scavenge on dead animal remains in ponds.

The larval period typically last around 5-9 weeks depending on site conditions such as temperature, food quality and quantity, and the density of tadpoles and their predators. Wright (1932) reported the larval period to last 38–55 days in southeastern Georgia. Experimental studies in cattle tanks and field enclosures show that crowding generally acts to reduce growth rates, lengthen the larval period, reduce survival to metamorphosis, and reduce the size of larvae at metamorphosis (Morin 1983a, Nicholson 1980, Wilbur et al. 1983). These responses are often influenced by the density and arrival time of predators such as newts in the ponds. Travis and Trexler (1986) grew tadpoles in field enclosures that were placed in different microhabitats in a pond that varied from poor to high quality and found that site quality can affect tadpole growth and density-dependent growth trajectories.

New metamorphosed toadlets vary substantially in size depending on site conditions. Wright (1932) collected individuals that were 6.5–10.5 mm SUL in Georgia, while Pechmann et al. (2001) reported averages of 13.5 and 16.8 mm (range = 9.3-24.0) for metamorphs from several ponds in South Carolina that were surrounded by drift fences. Because the toadlets often stay for several weeks at pond margins and feed before emigrating to uplands, the latter values are likely biased upwards.

Terrestrial Life History: The mature tadpoles tend to metamorphose synchronously at individual breeding sites. Dodd (2013) noted that at productive sites vast numbers of toadlets can sometimes be seen along shorelines, with waves of metamorphs dispersing to upland sites. Todd and Winne (2006) collected around 65,000 toadlets moving away from a breeding site in South Carolina, while DeGregorio et al. (2014) collected over 100,000. The juveniles often feed for a few weeks in wet habitats near the edges of breeding sites before emigrating to upland sites. They mostly disperse during the day and tend to move more during rainy weather. Dodd (1994) found that most metamorphs moved in random directions from a breeding site towards surrounding xeric hammock and sandhill habitats in north-central Florida.

The adults are capable of moving long distances to and from the breeding sites. Dodd (1996) captured individuals that bred in north-central Florida an average of 515 m from the water's edge, with the maximum capture distance of 914 m. Experimentally displaced individuals are capable of homing long distances back to their point of capture, which suggests that adults likely return to their home ranges after breeding. Bogert (1947), for example, found that 37% of toads that were released about 450 m from their capture site returned home, while 19% of those released one mile (1609 m) away successfully returned to their initial point of capture.

Anaxyrus terrestris is active on the ground surface year-round in many southern localities, particularly after periods of rain. Individuals are generally inactive during summer droughts and cold winter weather. During stressful conditions, they seek shelter by either burrowing into the ground or moving into sheltered sites such as mammal burrows, sawdust piles, rock piles, or leaf litter and piles of woody debris. Individuals are often diurnally active, but during the warmer months of the year tend to burrow in the soil or remain beneath surface cover during the day and forage at night (Dodd 2013). Toads that were tracked by Fritts et al. (2015) on a clearcut in Beaufort County, North Carolina used piles of coarse woody debris, as well as woody vegetation, herbaceous groundcover, and fine woody debris for their diurnal refuges.

The juveniles and adults are opportunistic generalists that feed on a wide variety of palatable invertebrates. Common prey that were found in a series of dietary studies in Florida included beetles, ants, true bugs, grasshoppers, earwigs, katydids, spiders and worms (Dodd 2013, Krakauer 1968, Meshaka and Mayer 2005, Meshaka and Powell 2010, Punzo 1992). The toads either ambush prey while resting and actively search for prey at night as they hop about. They are sometimes attracted to building and street lights where they feed on insects.

Data on the growth and age at sexual maturity are largely lacking. Wright (1932) estimated that toads in southeastern Georgia become sexually mature at about three years of age. Given the extended breeding season of this species, it is likely that many individuals mature after two years as is the case for many other toad species. More information is needed on this aspect of the life cycle.

General Ecology

Population Ecology: Local populations are often rather large and may exceed 500-1000 adults where larger breeding sites or cluster of breeding ponds are present (Dodd 2013). Factors that regulate local populations are poorly understood. Some populations appear to have episodic patterns of reproduction with little or no output of juveniles in many years due to drought or other causes (Dodd 1992, Greenberg and Tanner 2005, Greenberg et al. 2017, Semlitsch et al. 1996). In other years bumper crops may be produced where tens of thousands of toadlets leave the ponds. Dodd (2013) noted that mass metamorphosis can result in hundreds of thousands of toadlets moving across a landscape simultaneously in Florida. The extent to which density-dependent processes operate in the larval stage to regulate population size is not fully understood. Crowding likely plays a significant role since it results in stunted growth, higher larval mortality, and smaller metamorphs (Morin 1983, Nicholson 1980, Wilbur et al. 1983).

Community Ecology: The Southern Toad shares breeding sites with numerous predators and potential competitors (e.g., Atkinson et al. 2021). When placed in experimental communities in outdoor tanks, the larvae often compete for limited food resources with other anurans that have similar diets (Morin 1983, Wilbur et al. 1983). The larvae are poor competitors against Scapiophus holbrooki, but tend to outcompete other species such as Pseudacris crucifer and Hyla gratiosa. Salamander predators such as Ambystoma tigrinum larvae and adult Notophthalmus viridescens are highly efficient predators in experimental communities and can strongly mediate both intra-and interspecific competition among anurans that share tanks. The extent to which these results apply to natural breeding sites needs additional study.

Adverse Environmental Impacts

Habitat Loss: As with most amphibians, the loss and degradation of natural wetlands is one of the greatest threats to this species. Although population declines have occurred in highly urbanized areas like southeastern Florida (Meshaka and Powell 2010), the Southern Toad tolerates human-disturbed landscapes fairly well and uses many constructed wetlands such as farm ponds, flooded ditches and lakes.

Habitat Fragmentation: Habitat fragmentation does not appear to strongly adversely affect this species, which evolved to adapt to landscapes that are frequently disturbed by wildfires and severe storms.

Effects of Pollution: Metts et al. (2013) found that female toads that bred in an active coal combustion waste (CCW) disposal basin contained elevated levels of selenium, nickel, lead and other trace elements. These were transferred to the eggs and larvae where they reduced hatching success, offspring viability, and overall reproductive success. Similar adverse effects related to toxic chemicals in coal combustion waste have been reported by others (Hopkins et al. 1998, Rowe et al. 2001). Anzaldua and Goldberg (2020) found high levels of gross abnormalities in larvae of several species of frogs, including A. terrestris, in a suburban landscape in Florida that had received heavy applications of mosquito control insecticides for years.

Effects of Introduced Species/Induced Increases of Native Species: The Southern Toad has declined in southern Florida where introduced species like the South American Cane Toad (Rhinella marina) and Cuban Treefrog (Osteopilus septentrionalis) abound, but it is uncertain to what extent they are casual agents. Smith (2005) found that larval O. septentrionalis can potentially compete with A. terrestris larvae. Their presence acts to stunt growth, delay metamorphosis, and produce smaller individuals at metamorphosis. The South American Cane Toad and Southern Toad have a high degree of dietary overlap where syntopic and could potentially compete for limited food resources (Meshaka and Powell 2010). Punzo and Lindstrom (2001) noted that populations of this an other native anurans usually decline after R. marina becomes established in retention ponds in southern Florida. The eggs are toxic and tadpoles of A. terrestris and other native anurans that feed on them can suffer significant mortality.

Status in North Carolina

NHP State Rank: S5

Global Rank: G5

Environmental Threats: Many local populations of this species have undoubtedly been lost due to the destruction of wetlands, urbanization, and large-scale agricultural activities. Increased salinization of freshwater is a growing threat in coastal areas due to sea level rise. Wood and Welch (2014) found that tadpoles reared at elevated salinity were smaller, less active, and metamorphosed later and at a smaller average size than controls. Tadpoles were also negatively affected by exposure to the insecticide carbaryl, and their combined effects acted synergistically to produce the most deleterious outcomes.

Photo Gallery for Anaxyrus terrestris - Southern Toad		17 photos are shown.
	Recorded by: Mark Basinger Wilson Co.	Recorded by: H. Talcott Moore Co.
	Recorded by: Steve Hall and Jim Petranka Richmond Co.	Recorded by: Michael P. Morales Cumberland Co.
	Recorded by: Michael P. Morales Cumberland Co.	Recorded by: B. Bockhahn New Hanover Co.
	Recorded by: R. Newman Carteret Co.	Recorded by: Mark Basinger Wilson Co.
	Recorded by: Owen McConnell Moore Co. Comment: A possible hybrid (?) between A. terrestris and A. fowleri.	Recorded by: B. Bockhahn, J. Anderson Harnett Co.
	Recorded by: Salman Abdulali Pitt Co. Comment: A possible hybrid (?) between A. terrestris and A. fowleri.	Recorded by: Mark Shields Onslow Co.
	Recorded by: L. Garner Bladen Co.	Recorded by: T. Taylor New Hanover Co.
	Recorded by: T. Taylor New Hanover Co.	Recorded by: ASH Moore Co.
	Recorded by: J. Shimel, K. Futch New Hanover Co.

Anaxyrus terrestris - Southern Toad

Photo Gallery for Anaxyrus terrestris - Southern Toad

17 photos are shown.