Rana sphenocephala Cope, 1886
Southern Leopard Frog
Brian P. Butterfield1
Michael J. Lannoo2
1. Historical versus Current Distribution. Southern leopard frogs (Rana sphenocephala) are distributed throughout the southeastern quarter of the continental United States, exclusive of the Appalachian Highlands. Their range extends from central Texas and Oklahoma and eastern Kansas eastward to southeastern Iowa, central Illinois, and eastern Kentucky, south to include most of Missouri, Arkansas, Tennessee, Louisiana, Mississippi, Alabama, Georgia, South Carolina, and Florida (Garrett and Barker, 1987; Hoffman, 1990). Their range also extends up the Atlantic Coast to include the eastern 3/4 of North Carolina (see also Myers, 1924), eastern Virginia, Maryland, eastern Pennsylvania, and southeastern New York, including Long Island. Southern leopard frogs are common throughout most of Tennessee, but are limited in the east by the higher elevations of the Blue Ridge Mountains (Tennessee Animal Biogeographic System, 2000; fwie.fw.vt.edu/TN). Two subspecies of southern leopard frogs (R. sphenocephala) are recognized: Florida leopard frogs (R. s. sphenocephala Cope, 1886) are found in Florida, especially on the peninsula; southern leopard frogs (R. s. utricularia) occupy the remainder of the distribution (Crother et al., 2000). Male Florida leopard frogs retain vestigial oviducts (Bartlett and Bartlett, 1999a). While a comparison of historical and current ranges has not been made, Hudson (1956) comments that southern leopard frogs occur "…only in isolated localities now undergoing modifications due to industrial expansion."
2. Historical versus Current Abundance. Bartlett and Bartlett (1999a) state that these are the most abundant frogs in Florida. Mount (1975) notes that they are the most ubiquitous frogs in Alabama, but recent declines have been noted. The Tennessee Animal Biogeographic System (2000) states that southern leopard frogs are common throughout much of the state, but apparently are limited in the east by the higher elevations of the Blue Ridge Mountains.
3. Life History Features.
A. Breeding. Reproduction is aquatic.
i. Breeding migrations. Southern leopard frogs breed in early spring in the North, and at any month of the year in the South (Mount, 1975; Conant and Collins, 1991; Doody and Young, 1995) following rainfalls (Doody and Young, 1995), although Mount (1975) notes that most breeding in Alabama occurs from December–March. Johnson (1992) states that southern leopard frogs in Missouri are known to breed in the autumn. Caldwell (1986) summarizes what is known by stating that although southern leopard frogs will breed throughout the year, in the South there are usually two major breeding periods—the first in early fall in September–October and the second from November–February or March. In the North, only one breeding season is typical, in the spring following ice melt. Caldwell (1986) notes exceptions: in Kansas southern leopard frogs breed in September and March, while in Missouri (D. Seale, personal communication) they breed in autumn and spring. Males occasionally will call when submerged or from crawfish burrows (Palis, 2000b). Following breeding, southern leopard frogs disperse throughout upland habitats (Brandt, 1936a).
ii. Breeding habitat. Males call while floating in open water from emergent vegetation or while perched on logs or sticks (Wright, 1932). Egg masses are laid in shallow, non-flowing waters (Hillis, 1982; Behler and King, 1998), which are usually fishless. Masses are typically partly floating and attached to vegetation (Wright, 1932).
i. Egg deposition sites. Eggs are found most often adhering to submergent or emergent vegetation (Caldwell, 1986; Ashton and Ashton, 1988; Bartlett and Bartlett, 1999a). Eggs hatch in 4–5 d in Florida (Ashton and Ashton, 1988) and ≤ 2 wk in Missouri (Johnson, 1992). Caldwell (1986) documented communal nesting during the cold breeding season, and suggested that this confers a thermal advantage to the eggs that is necessary to develop and survive in cold temperatures. Eggs hatch in 3–5 d (Wright, 1932). Eggs exhibit accelerated hatching times in the presence of crayfish (Procambarus nigrocinctus) predators (Saenz et al., 2003). Rapid pond drying is a threat to eggs (Wright, 1932).
ii. Clutch size. "The complement of a large female might reach 1,200–1,500 eggs or even more" (Wright, 1932), [5,000 according to Johnson, 1992]. Egg diameter ranges from 1.5–1.8 mm (vitellus).
i. Length of larval stage. From 50–75 d (Wright, 1932); "About three months" (Ashton and Ashton, 1988). Johnson (1992) notes that in Missouri, metamorphosis usually takes place from mid June to late July.
ii. Larval requirements.
a. Food. Where southern leopard frogs and Rio Grande leopard frogs (R. berlandieri) co-occur, southern leopard frog tadpoles ingest mainly green algae and many fewer diatoms than Rio Grande leopard frog tadpoles (Hillis, 1982). Low food levels elicit interference mechanisms (production of growth inhibitors) among southern leopard frog tadpoles, while high food levels elicit exploitative competition (Steinwascher, 1978b; Alford and Crump, 1982).
b. Cover. Aquatic macrophytes and emergent vegetation provide cover for tadpoles.
iii. Larval polymorphisms. Do not occur.
iv. Features of metamorphosis. Across their range, metamorphosis occurs during every month from April–October (Wright, 1932). Metamorphosing animals generally are small, but sizes vary and range from 20–33 mm (Wright, 1932). Southern leopard frog tadpoles will shorten their time as larvae in response to wetland drying (Parris, 1997).
v. Post-metamorphic migrations. From breeding sites to upland feeding sites.
D. Juvenile Habitat. Similar to adults, although juveniles may seek wetter habitats.
E. Adult Habitat. All types of shallow freshwater habitats, including temporary pools, cypress ponds, ponds, lakes, ditches, irrigation canals, and stream and river edges; will inhabit slightly brackish coastal wetlands (Wright and Wright, 1949; Garrett and Barker, 1987; Hoffman, 1990; Conant and Collins, 1991; Bartlett and Bartlett, 1999a; Tennessee Animal Biogeographic System, 2000). In North Carolina, Pearse (1911) reported southern leopard frogs in 2.14‰ saltwater (see also Voice, 1923; Liner, 1954; Dundee and Rossman, 1989). Bartram (1791, in Wright, 1932) notes that in southern Pennsylvania, southern leopard frogs abound in rivers, swamps, and marshes. Hoffman (1990) concluded that southern leopard frogs occur chiefly, if not exclusively, along the floodplains of larger rivers in the western Piedmont. Southern leopard frogs will move into terrestrial habitats to feed during the summer, when vegetation in pastures, fields, and sod lands affords shade and shelter (Brandt, 1936a; Conant and Collins, 1991; Johnson, 1992; Bartlett and Bartlett, 1999a). Primarily nocturnal. Annual periods of activity range from nearly year-round in the south to winter dormancy in the north (Wright, 1932).
F. Home Range Size. Unknown.
G. Territories. Unknown and unlikely.
H. Aestivation/Avoiding Dessication. Similar to northern leopard frogs, southern leopard frogs seek moist areas, such as springs, river edges, and lake margins during dry periods.
I. Seasonal Migrations. To and from breeding sites in the spring, post-metamorphic migrations from breeding wetlands to upland feeding sites, and, where necessary, to winter refugia in permanent water bodies.
J. Torpor (Hibernation). Occurs in northern populations. Overwintering sites include permanent, well-oxygenated bodies of water.
K. Interspecific Associations/Exclusions. In Missouri, southern leopard frogs will occur and sometimes hybridize with plains leopard frogs (R. blairi; Johnson, 1992). In Louisiana, Dundee and Rossman (1989) note that bronze frogs (R. clamitans clamitans) will displace southern leopard frogs in wet woods and swamps. In Virginia, Pague and Buhlman (1992) note southern leopard frogs in association with carpenter frogs (R. virgatipes), northern leopard frogs (R. pipiens), pickerel frogs (R. palustris), and green frogs (R. clamitans). Southern leopard frogs and Rio Grande leopard frogs breed in the same wetlands—Rio Grande leopard frogs usually breed several months before southern leopard frogs—and tadpoles co-occur (Wright and Wright, 1949). Pickens (1927b) suggests intergrades between northern and southern leopard frogs.
L. Age/Size at Reproductive Maturity. From 51–127 mm SVL (Conant and Collins, 1991; Johnson, 1992; see also Springer, 1938).
M. Longevity. Unknown; Snider and Bowler (1992) do not list southern leopard frogs in their compilation. A scan of Snider and Bowler's (1992) data for similarly sized ranids reveals great variation, from < 2 to 6 yr, in longevity, and so is not helpful in formulating an estimation for southern leopard frogs.
N. Feeding Behavior. Southern leopard frogs will feed in upland habitats during the summer, where they take insects and a variety of other invertebrate prey (Johnson, 1992). In general, the food habits of southern leopard frogs resemble those of northern leopard frogs (Rana pipiens; Wright, 1932) and include a variety of insects and other aquatic invertebrates including crayfish (Force, 1925).
O. Predators. Southern leopard frogs are often hunted for their legs (Mount, 1975; Helfrich et al., 1997; Behler and King, 1998). Ashton and Ashton (1988) state that southern leopard frogs are too small to be taken for their legs, but are captured in large numbers for use in the bait industry, by scientific researchers, and for classroom teaching. They also note that southern leopard frogs, along with southern cricket frogs (Acris gryllus), are "undoubtedly an important food item in the diet of many aquatic predators." Wright (1932) records predators as including great blue herons (Ardea herodias), grackles (Quiscalus sp.), southern water snakes (Nerodia fasciata), brown water snakes (N. taxispilota), northern black snakes (Coluber constrictor constrictor), peninsular ribbon snakes (Thamnophis sauritus sackenii), and water moccasins (Agkistrodon piscivorus).
P. Anti-Predator Mechanisms. When frightened and when adjacent to water, southern leopard frogs will dive into the water, make a sharp angled turn while submerged, and surface among vegetation away from the predator's gaze (Behler and King, 1998). When frightened on land, they resemble northern leopard frogs in making a series of low leaps, each in a different direction (Bartlett and Bartlett, 1999a). Wright (1932) comments that southern leopard frogs are alert, active, agile, and hard to capture in water or on land. Further, when they are alarmed while resting on a bank of a stream or a pond, southern leopard frogs usually escape inland.
Q. Diseases. Southern leopard frogs are susceptible to agrichemical applications in combination with UV-B exposure in mesocosm experiments (Britson and Threlkeld, 1998b). They are also sensitive to the interactive toxicity of petroleum hydrocarbons and solar radiation (Little et al., 1998).
Sparling (1998) reported an increase in hindlimb, orbital, and pigment malformations in southern leopard frogs in response to altosid applications. McCallum (1999) notes a site in southern Illinois characterized by malformed southern leopard frogs with multiple malformations, including missing limbs, partial limbs, complete but malformed limbs, duplicated limb segments, and missing eyes.
R. Parasites. Apparently not well studied. The respiratory tracts of some ranid frogs are susceptible to infection by a group of lung worms in the genus Rhabdias (Baker, 1978a).
4. Conservation. Southern leopard frogs exhibit a broad distribution throughout the southeastern United States and are not considered a species of conservation concern by any state or the Federal Government. They are considered the most abundant frogs in Florida (Bartlett and Bartlett, 1999a) and the most ubiquitous frogs in Alabama (Mount, 1975). The Tennessee Animal Biogeographic System (2000) states that southern leopard frogs are common throughout much of this state, but are apparently limited in the east by the higher elevations of the Blue Ridge Mountains. Hudson (1956) notes that habitat destruction may be restricting southern leopard frogs to isolated localities.
1Brian P. Butterfield
Department of Biology
Henderson, Tennessee 38340-2399
2Michael J. Lannoo
Muncie Center for Medical Education
Indiana University School of Medicine
Ball State University
Muncie, Indiana 47306
USGS-Patuxent Wildlife Research Center
12100 Beech Forest Road
Laurel, Maryland 20708-4031
Literature references for Amphibian Declines: The Conservation Status of United States Species, edited by Michael Lannoo, are here.
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