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The Nonindigenous Occurrences section of the NAS species profiles has a new structure. The section is now dynamically updated from the NAS database to ensure that it contains the most current and accurate information. Occurrences are summarized in Table 1, alphabetically by state, with years of earliest and most recent observations, and the tally and names of drainages where the species was observed. The table contains hyperlinks to collections tables of specimens based on the states, years, and drainages selected. References to specimens that were not obtained through sighting reports and personal communications are found through the hyperlink in the Table 1 caption or through the individual specimens linked in the collections tables.

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Common name: American Bullfrog

Synonyms and Other Names: Rana catesbeiana, Rana mugiens, Rana scapularis

Taxonomy: available through www.itis.gov

Identification: Lithobates catesbeianus is the largest true frog native to Eastern North America (Dorcas and Gibbons 2008). Adults range in size between 9 and 15.2 cm (snout vent length) (Powell et al. 2016). Lithobates catesbeianus can be identified by their green or olive smooth skin, often with dark mottling on their backs, while their stomachs are white to cream mottled with dark pigment (Dorcas and Gibbons 2008).  The back of the thighs are flecked with small light spots (Johnson 2007). The hind feet are webbed with the longest toe extending past the webbing (Johnson 2007; Powell et al. 2016). The dorsolateral ridge (ridge around eardrum) that can be found behind the tympanum (eardum) is absent in L. catesbeianus (Dorcas and Gibbons 2008; Powell et al. 2016). Female L. catesbeianus have tympanum approximately the same size as their eye, while males have tympanum twice as large (Dorcas and Gibbons 2008). This is the only species in the southeast U.S. with males larger than females (Dorcas and Gibbon 2008). Tadpoles can be differentiated from other frog species by their large size (approximately 15 cm), olive green color, scattered black dots, and lack of visible intestinal coil (Dorcas and Gibbons 2008). The call of L. catesbeianus is described as a series of deep bass notes (Powell et al. 2016) Lithobates catesbeianus may be confused with other native species, such as the River frog, Lithobates heckscheri, which is darker brown with white spots on the lower lip and dark spots on the upper lip (Dorcas and Gibbons 2008). Pig frogs, Lithobates grylio, are commonly confused with L. catesbeianus, however pig frogs have a more pointed snout and the webbing on their hind feet extends the whole length of the longest toe (Dorcas and Gibbons 2008). Juvenile bullfrogs may be confused with green frogs, Hyla cinerea; however, green frogs have a dorsolateral (on back and sides) ridge extending at least partially down its body (Dorcas and Gibbons 2008).

Size: 9 - 15.2 cm

Native Range: : Native to the eastern United States, but historically absent from the Cape Cod archipelago and associated islands. Not historically present in the southern portion of Florida or the Okefenokee Swamp (Dorcas and Gibbons 2008).

Alaska	Hawaii	Puerto Rico & Virgin Islands	Guam Saipan

Hydrologic Unit Codes (HUCs) Explained
Interactive maps: Point Distribution Maps

Ecology: Lithobates catesbeianus are habitat generalists and can be found in permanent aquatic habitats such as, ponds, lakes, reservoirs, backwater rivers, ditches, swamps, marsh, bogs, cattle tanks, irrigation canals, and occasionally temporary water bodies (Dorcas and Gibbons 2008; Powell et al. 2016). Juveniles can disperse large distances overland (Dorcas and Gibbons 2008). Adult home ranges have been estimated to be approximately 1.6 km (Cooper 2017).
This species hibernates buried in the mud underwater, while some individuals may overwinter in burrows on land and emerge later in the spring than most true frogs (Powell et al. 2016). The persistence of water bodies is essential for tadpoles to mature and overwinter (Dorcas and Gibbons 2008).
Lithobates catesbeianus are nocturnal generalist predators and have been shown to consume various prey including insects, leeches, centipedes, scorpions, fishes, other frogs, small alligators, turtles, snakes, rodents, bats, birds, and juvenile mink (Kats and Ferrer 2003; Dorcas and Gibbons 2008; Flynn et al. 2017). Bullfrogs have also been known to cannibalize in dense populations (Dorcas and Gibbons 2008; Flynn et al. 2017). Bullfrog tadpoles’ chemical cues affect behavior of native larvae (Kiesecker and Blaustein 1997; Anderson and Lawler 2016). This species also serves as a host to the glochidia of native unionid mussel Utterbackis imbecilis, the paper pondshell (Watters and O’Dee 1998).
Female L. catesbeianus can lay 6,000-20,000 eggs at a time (Urbina et al. 2020). Eggs hatch in 2-5 days and can take four months up to two years to metamorphosize (Urbina et al. 2020). In the bullfrog’s native southern U.S. range, breeding occurs from February – October (Urbina et al. 2020.) However, breeding is limited to the warm summer months in introduced populations in the Pacific northwest (Urbina et al. 2020).

Means of Introduction: Lithobates catesbeianus was introduced to the West Coast of the U.S. as a food source in the 1850s (Jennings and Hayes 1985). It is also thought that accidental introduction through fish stocking may have also contributed to the spread in the western U.S. Lithobates catesbeianus was introduced globally as a food source and through aquaculture escape (Ottens 2016). 
 

Status: In the U.S. Lithobates catesbeianus is established in coastal regions along the west coast in Washington, Oregon, and California. There have also been populations found in Arizona, New Mexico, Colorado, Nebraska and Montana. In the eastern U.S., the species has been introduced to Maine, Rhode Island, Iowa, Minnesota, and Southern Florida. Lithobates catesbeianus has spread globally to Europe, Asia, and South America and has been ranked among the top 100 of the world’s worst invasive species (Lowe et al. 2000; Giovanelli et al. 2008).

Impact of Introduction:

Summary of species impacts derived from literature review. Click on an icon to find out more...

Ecological	Economic	Other

Lithobates catesbeianus prey on native frog species in their introduced range and jeopardize endemic pupfish through predation and competition (Jameson 1956; U.S. Department of Interior Desert Pupfish Task Force 1971; Dumas 1996). Presence of this species can lead to decreased breeding in populations of the native northern leopard frog,  Lithobates pipiens. (Johnson et al. 2011). Larval bullfrogs may also affect nutrient cycling by altering levels of phosphorus and nitrogen in the water column (Guariento et al. 2018).  Lithobates catesbeianus is known to spread fatal Chytrid fungus; Batrachochytrium dendrobatidis, and cotton moulds, Saprolegnia ferax (Yap et al. 2018). In its native range L. catesbeianus is also a host to Lernaea cyprinacea (European copepod parasite) (Matson 2019). This parasite may pass to other species of frogs and fishes and cause death (Khalifa and Post 1976; Matson 2019). Lithobates catesbeianus are farmed commercially for harvest and hunted in their nonnative range (Jennings and Hayes 1994; Treanor and Nicola 1972). Individuals have been hired to eradicate L. catesbeianus in East Kootney, Canada (Anonymous 2023).

Remarks: The genus Rana was revised, and North, Central, and South American “true frogs” were placed into the genus Lithobates (Frost et al. 2006). In 2005 the National Park Service in Yosemite Valley, Yosemite National Park started using eDNA paired with audio recording devices to detect bullfrogs and subsequently remove them. This long-term eradication and monitoring effort is the first successful bullfrog removal at the landscape level and allowed for the reintroduction of the federally endangered Rana draytonii (California red-legged frog) to Yosemite Valley in 2016 (Kamoroff et al. 2020). Another control method for this species that is being investigated is the sterile male release technique, sterile males are released into the population to reduce breeding (Descamps and De Vocht 2022).

References: (click for full references)

Anderson, R.B. and S.P. Lawler. 2016. Behavioral changes in tadpoles after multigenerational exposure to an invasive intraguild predator. Behavioral Ecology 27(6):1790-1796. https://doi.org/10.1093/beheco/arw112.

Anonymous. 2023. Experts leap into action to protect endangered leopard frogs. East Kootenay News Online Weekly. https://www.e-know.ca/regions/ktunaxa-nation/experts-leap-into-action-to-protect-endangered-leopard-frogs/. Created on 04/08/2023. Accessed on 04/26/2023.

Cooper, M. 2017. Movement, habitat, and home range of introduced bullfrogs (Lithobates catesbeianus) on Mad River gravel ponds (Humboldt Co., Ca, USA), with implications for hydro-modification as a method of management. Unpublished M.S. thesis. Humboldt State University, Humboldt, CA.

Descamps, S., and A. De Vocht. 2022. Bisazir as a chemosterilant to control invasive vertebrates: ecotoxicity and efficacy to induce male sterility in Lithobates catesbeianus. Management of Biological Invasions 13(4):769-780. https://doi.org/10.3391/mbi.2022.13.4.12.

Dorcas, M., and W. Gibbons. 2008. Frogs and toads of the southeast. The University of Georgia Press 238 pp.

Dumas, P.C. 1966. Studies of the Rana species complex in the Pacific northwest. Copeia 1966(1):60-74. https://www.jstor.org/stable/1440762.

Flynn, L.M., T.M. Kreofsky, and A.J. Sepulveda. 2017. Introduced American Bullfrog distribution and diets in Grand Teton National Park. Northwest Science 91(3):244-256. https://doi.org/10.3955/046.091.0305.

Frost, D., T. Grant, J. Faivovich, R. Bain, A. Haas, C. Haddad, R. De Sá, A. Channing, M. Wilkinson, S. Donnellan, C. Raxworthy, J. Campbell, B. Blotto, P. Moler, R.C. Drewes, R. Nussbaum, J. Lynch, D. Green & W. Wheeler. 2006. The amphibian tree of life. Bulletin of the American Museum of Natural History 297:1-370. http://www.cnah.org/pdf_files/491.pdf.

Giovanelli, J.G.R., C.F.B. Haddad, and J. Alexandrino. 2008. Predicting the potential distribution of the alien invasive American bullfrog (Lithobates catesbeianus) in Brazil. Biological Invasions 10:585-590

Guariento, R.D., L.S. Carneiro, J.S. Jorge and A. Caliman. 2018. Assessing the risk effects of native predators on the exotic American bullfrog (Lithobates catesbeianus) and their indirect consequences to ecosystem function. Acta Oecologica 91:50-56. https://doi.org/10.1016/j.actao.2018.06.004.

Jameson, D.L. 1956. Growth, dispersal and survival of the Pacific tree frog. Copeia 1:25-29. https://www.jstor.org/stable/1439240.

Jennings, M.R, and Hayes, M.P. 1994. Amphibian and reptile species of special concern in California. California Department of Fish and Game, Inland Fisheries Division, Rancho Cordova, CA.

Jennings, M.R., and M.P. Hayes. 1985. Pre-1900 overharvest of California red-legged frogs (Rana aurora draytonii): the inducement for bullfrog (Rana catesbeiana) introduction. Herpetologica 41(1):94-103.

Johnson, S.A. 2007. "True" frogs (family Ranidae). https://ufwildlife.ifas.ufl.edu/frogs/americanbullfrog.shtml. Created on 01/13/2020. Accessed on 01/11/2024.

Johnson, P.T.J., V.J. McKenzie, A.C. Peterson, J.L. Kerby, J. Brown, A.R. Blaustein, and T. Jackson. 2011. Regional decline of an iconic amphibian associated with elevation, land-use change, and invasive species. Conservation Biology 25(3):556-566. http://onlinelibrary.wiley.com/doi/10.1111/j.1523-1739.2010.01645.x/pdf.

Kamoroff, C., N. Daniele, R.L. Grasso, R. Rising, T. Espinoza, and C.S. Goldberg. 2020. Effective removal of the American bullfrog (Lithobates catesbeianus) on a landscape level: long term monitoring and removal efforts in Yosemite Valley, Yosemite National Park. Biological Invasions 22:617-626. https://doi.org/10.1007/s10530-019-02116-4.

Kats, L.B., and R.P. Ferrer. 2003. Alien predators and amphibian declines: review of two decades of science and the transition to conservation. Diversity and Distributions 9(2):165-163. https://doi.org/10.1046/j.1472-4642.2003.00013.

Khalifa, K.A. and G. Post. 1976. Histopathological effect of Lernaea cyprinacea (a copepod parasite) on fish. The Progressive Fish-Culturist 38(2):110-113. https://doi.org/10.1577/1548-8659(1976)38[110:HEOLCA]2.0.CO;2.
Kiesecker, J.M., and A.R. Blaustein. 1997. Population differences in responses of red-legged frogs (Rana aurora) to introduced bullfrogs. Ecology 78(6):1752-1760. http://links.jstor.org/sici?sici=0012-9658%28199709%2978%3A6%3C1752%3APDIROR%3E2.0.CO%3B2-B.

Lowe, S., M. Browne, S. Boudjelas, and M. De Poorter. 2000. 100 of the World's Worst Invasive Alien Species: A selection from the global invasive species database. The Invasive Species Specialist Group (ISSG) a specialist group of the Species Survival Commission (SSC) of the World Conservation Union. www.issg.org/booklet.pdf.

Matson, T.O. 2019. Infection of American Bullfrog Tadpoles, Lithobates catesbeianus (Shaw), by Anchor Worm, Lernaea cyprinacea L., in Streams of Northeastern Ohio. Ohio Biological Survey Notes 9:35-40. http://ohiobiologicalsurvey.org/wp-content/themes/ohio/images/Matson_2019_3.pdf.

Ottens, R. 2016. Species at a glance; American bullfrog. https://seagrant.oregonstate.edu/sites/seagrant.oregonstate.edu/files/bf-species-guide.pdf. Accessed on 01/11/2024.

Powell, R., R. Conant, and J.T. Collins. 2016. Peterson field guide to reptiles and amphibians of eastern and central North America. 4th edition. Houghton Mifflin Harcourt Publishing Company, New York, NY.

Treanor, R.R., and S.J. Nicola, S.J. 1972. A Preliminary Study of the Commercial and Sporting Utilization of the Bullfrog, Rana catesbeiana Shaw, in California. California Department of Fish and Game.

Urbina, J., E.M. Bredeweg, C. Cousins, A.R. Blaustein, and T.S. Garcia. 2020. Reproductive characteristics of American bullfrogs (Lithobates catesbeianus) in their invasive range of the Pacific Northwest, USA. Scientific Reports 10:16271. https://doi.org/10.1038/s41598-020-73206-w.

U.S. Department of Interior Desert Pupfish Task Force. 1971. Status of the desert pupfish. U.S. Department of Interior, Washington, D.C. https://ecos.fws.gov/ServCat/DownloadFile/56698.

Watters, T.G., and S.H. O’Dee. 1998. Metamorphosis of freshwater mussel glochidia (Bivalvia: Unionidae) on amphibians and exotic fishes. American Midland Naturalist 139:49-57.

Watters, T.G., and S.H. O'Dee. 1998. Metamorphosis of freshwater mussel glochidia (Bivalvia: Unionidae) on amphibians and exotic fishes. American Midland Naturalist 139:49-57.

Yap, T.A., M.S. Koo, R.F. Ambrose, and V.T. Vredenberg. 2018. Introduced bullfrog facilitates pathogen invasion in the western United States. PLoS ONE 13(4):e0188384. https://doi.org/10.1371/journal.pone.0188384.

Other Resources:
US Fish and Wildlife Service Ecological Risk Screening Summary for Lithobates catesbeianus

Author: Audrey Jordon

Peer Review Date: 3/21/2024

This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.