Animal Diversity Web

Geographic Range

The river frog can be found in the southeastern portion of the United States. It is found in parts of the following states: Mississippi, Alabama, Georgia, Florida, South Carolina and North Carolina (FCES 1999).

• Biogeographic Regions
• nearctic
  • native

Habitat

The river frog is not limited to rivers as its name may imply. They can also be found in and along lakes, ponds, swamps, streams, and marshes. They prefer open, thinly vegetated shoreline habitats (Bartlett and Bartlett 1999).

• Aquatic Biomes
• lakes and ponds

Physical Description

The river frog ranges from 3.25 - 4.63 inches in snout-vent length (record length 6.13 inches). The dorsal surface of the frog is a greenish black color. A common field mark is the presence of light spots on the lips; these spots are usually larger on the lower jaw. The skin is more rugose than the skin of most other ranid frogs. The belly ranges from gray to almost black in color, and is marked with light spots or short wavy lines (Conant and Collins 1998). Males often have a yellowish suffusion on the throat. The river frog has no dorsolateral ridges as found in many other ranid frogs. The webbing on the hind feet extend to the last phalanx on the longest toe (Bartlett and Bartlett 1999). Tadpoles of the river frog are rather large, reaching 4 inches before metamorphosis. The tadpoles undergo ontogenetic color changes. Small tadpoles have well-defined light rings around the body, posterior to the eyes, these rings disappear with growth (Bartlett and Bartlett 1999).

• Other Physical Features
• ectothermic
• bilateral symmetry

Development

• Development - Life Cycle
• metamorphosis

Reproduction

Male river frogs call to attract local females from April into July. The call of larger more mature frogs is a deep, low pitched, roaring snore. Smaller males give off a much higher pitched call than do the larger males. The males will call while sitting in shallow water or on the shore near the waters edge (Bartlett and Bartlett 1999). When the male attracts a female they will go into amplexus. The male will use his enlarged thumbs to grasp the female while fertilizing the eggs as she deposits them (Wright 1932). The female will lay several thousand eggs that form into a surface film, often among emergent vegetation to which they adhere. The tadpoles overwinter and take about one year to metamorphose (Bartlett and Bartlett 1999).

• Key Reproductive Features
• gonochoric/gonochoristic/dioecious (sexes separate)

Behavior

The river frog is a highly aquatic frog, but can be approached rather easily. They often sit in shallow open water, and on structures such as logs, where they are highly visible to potential predators (Bartlett and Bartlett 1999).

• Key Behaviors
• motile

Food Habits

The river frog feeds largely on insects and other invertebrates; they occasionally take small vertebrate prey, such as other ranid frogs of suitable size.

Economic Importance for Humans: Positive

The river frog are an important species for their aesthetic value, ecological importance, and the consumption of insects, some of which are considered to be pests by humans.

Economic Importance for Humans: Negative

The river frog does not appear to present any negative attributes concerning the environment or humans.

Conservation Status

The river frog is still common in areas of the southeastern United States that still have proper habitat. With the preservation of their habitat the river frog should have no problem persisting in the future (Bartlett and Bartlett 1999).

• IUCN Red List

  Least Concern
  More information

• US Federal List

  No special status

Other Comments

Most frogs will try to flee and escape when captured; this is not the case with the river frog. Instead of trying to escape, the River Frog often will simply go limp and play dead. Another defense mechanism of this frog is to secrete a noxious and odorus substance onto its attacker (USGS 1999).

The tadpoles of the river frog are larger than those of most species, reaching a length of 4 inches before metamorphosis. The tadpoles also organize themselves into schools, which is not common among ranid frogs or among large tadpoles of any kind (Altig 1981). Schooling may be an anti-predator mechanism; i.e., safety in numbers (Bartlett and Bartlett 1999). Another proposed benefit is that schooling creates social facilitation among the tadpoles which is beneficial to their survival (Altig 1981).

Contributors

Jerry Hill (author), Michigan State University, James Harding (editor), Michigan State University.

References

USGS. 1999.. "River Frog; Rana heckscheri" (On-line). Accessed November 14, 1999 at http://www.mbr.nbs.gov/geotech/usfrogs/FRIVE.gif.

Florida Cooperative Extension Service. 1999.. "Wildlife; Frogs & Toads of Florida" (On-line). Accessed November 14, 1999 at http://www.wec.ufl.edu/extension/.

Altig, R., M. Christensen. 1981. Behavioral characteristics of the tadpoles of Rana heckscheri. Journal of Herpetology, 15 (2): 151-154.

Bartlett, R., P. Bartlett.. 1999. A Field Guide to Florida Reptiles and Amphibians. Houston: Gulf Publ. Co..

Conant, R., J. Collins. 1998. A Field Guide to Reptiles and Amphibians; Eastern/Central North America. New York: Houghton Mifflin Company.

Wright, A. 1932. Life-Histories of the Frogs of Okefinokee Swamp, Georgia. New York: The Macmillan Company.