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American Bullfrog - Lithobates catesbeianus
Other Names:  Bullfrog

Aquatic Invasive Species
Non-native Species

Global Rank: G5
State Rank: SNA
(see State Rank Reason below)

Agency Status


External Links

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Copyright by Canadian Amphibian and Reptile Conservation Network
State Rank Reason (see State Rank above)
A conservation status rank is not applicable because this species is not a suitable target for conservation activities as a result of being exotic or introduced.
General Description
Adult American Bullfrogs are a large frog usually pale to dark green or brownish-green with darker spots or blotches above; the underside is cream to yellowish with gray mottling. A series of black bands often extends across the legs. Body length may reach 8 inches. American Bullfrogs do not have ridges running along the sides of the back, but have prominent ridges running from the eyes over the external ear drums to the shoulders. Egg masses (a one- to-two-egg-thick film of thousands of eggs) may reach several feet across. Tadpoles, which grow to a length of 4.5 inches, are olive-green with numerous black spots above and white or cream with varying amounts of dark mottling below. American Bullfrogs are not native to Montana.

Diagnostic Characteristics
As sexual maturity approaches in males the upper abdomen temporarily turns yellowish in color (Flores-Nava, 2005). American bullfrogs have conspicuous tympanic membranes (eardrums). Mature males have tympanums twice the diameter of the eye, while mature females have tympanums about the same diameter as the eye (National Research Council, 1974). Males are also slightly smaller than females and have darkly pigmented thumb pads in contrast to the more delicate streamlined thumb of the female (National Research Council, 1974).

Species Range
Montana Range


Western Hemisphere Range


Range Comments
Native Range: Eastern United States to Minnesota and eastern Colorado south to Texas, but historically absent from the Cape Cod archipelago and associated islands off the east coast.

Introduced Range: From Washington, northern Idaho and Montana on the westslope of the continental divide in Colorado, New Mexico to Nevada, California and Arizona in the south.

Montana's Bitteroot River and Flathead River basin populations have been established since the 1960's (Werner et al. 2004), but the Yellowstone River populations have been a later introduction (2000's) with the epicenter being in Billings and expansion downstream (Sepulveda et al. 2015).

For maps and other distributional information on non-native species see:
Nonindigenous Aquatic Species Database from the U.S. Geological Survey
Invasive Species Habitat Tool (INHABIT) from the U.S. Geological Survey
Invasive Species Compendium from the Centre for Agriculture and Bioscience International (CABI)
EDDMapS Species Information EDDMapS Species Information

Observations in Montana Natural Heritage Program Database
Number of Observations: 464

(Click on the following maps and charts to see full sized version) Map Help and Descriptions
Relative Density



(Observations spanning multiple months or years are excluded from time charts)

Adult and juvenile bullfrogs may migrate overland to find other suitable aquatic habitats, if their existing wetland or pond habitat dries or is undergoing desiccation.

American Bullfrogs are found in lakes, ponds, cattle tanks, bogs, oxbow wetlands and sluggish portions of streams and rivers. American Bullfrogs are rarely seen far from the water's edge and are usually in the water. They are associated with larger bodies of quiet water; such as ponds, lakes, or backwaters of streams, usually in areas with extensive cattails or reeds. Their loud, deep "jug o'rum" call can be heard from a considerable distance. American Bullfrogs are voracious feeders, eating anything smaller than themselves, including ducklings, fish, mice, frogs, and small turtles. They have been implicated in extirpations of native frogs and turtles, and declines in waterfowl production. They are found in ponds, wetlands and rivers in the valleys. In the Northwest they have so far been unable to invade colder, higher elevation waters.

Ecological Systems Associated with this Species
  • Details on Creation and Suggested Uses and Limitations
    How Associations Were Made
    We associated the use and habitat quality (common or occasional) of each of the 82 ecological systems mapped in Montana for vertebrate animal species that regularly breed, overwinter, or migrate through the state by:
    1. Using personal observations and reviewing literature that summarize the breeding, overwintering, or migratory habitat requirements of each species (Dobkin 1992, Hart et al. 1998, Hutto and Young 1999, Maxell 2000, Foresman 2012, Adams 2003, and Werner et al. 2004);
    2. Evaluating structural characteristics and distribution of each ecological system relative to the species' range and habitat requirements;
    3. Examining the observation records for each species in the state-wide point observation database associated with each ecological system;
    4. Calculating the percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system to get a measure of "observations versus availability of habitat".
    Species that breed in Montana were only evaluated for breeding habitat use, species that only overwinter in Montana were only evaluated for overwintering habitat use, and species that only migrate through Montana were only evaluated for migratory habitat use.  In general, species were listed as associated with an ecological system if structural characteristics of used habitat documented in the literature were present in the ecological system or large numbers of point observations were associated with the ecological system.  However, species were not listed as associated with an ecological system if there was no support in the literature for use of structural characteristics in an ecological system, even if point observations were associated with that system.  Common versus occasional association with an ecological system was assigned based on the degree to which the structural characteristics of an ecological system matched the preferred structural habitat characteristics for each species as represented in scientific literature.  The percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system was also used to guide assignment of common versus occasional association.  If you have any questions or comments on species associations with ecological systems, please contact the Montana Natural Heritage Program's Senior Zoologist.

    Suggested Uses and Limitations
    Species associations with ecological systems should be used to generate potential lists of species that may occupy broader landscapes for the purposes of landscape-level planning.  These potential lists of species should not be used in place of documented occurrences of species (this information can be requested at: or systematic surveys for species and evaluations of habitat at a local site level by trained biologists.  Users of this information should be aware that the land cover data used to generate species associations is based on imagery from the late 1990s and early 2000s and was only intended to be used at broader landscape scales.  Land cover mapping accuracy is particularly problematic when the systems occur as small patches or where the land cover types have been altered over the past decade.  Thus, particular caution should be used when using the associations in assessments of smaller areas (e.g., evaluations of public land survey sections).  Finally, although a species may be associated with a particular ecological system within its known geographic range, portions of that ecological system may occur outside of the species' known geographic range.

    Literature Cited
    • Adams, R.A.  2003.  Bats of the Rocky Mountain West; natural history, ecology, and conservation.  Boulder, CO: University Press of Colorado.  289 p.
    • Dobkin, D. S.  1992.  Neotropical migrant land birds in the Northern Rockies and Great Plains. USDA Forest Service, Northern Region. Publication No. R1-93-34.  Missoula, MT.
    • Foresman, K.R.  2012.  Mammals of Montana.  Second edition.  Mountain Press Publishing, Missoula, Montana.  429 pp.
    • Hart, M.M., W.A. Williams, P.C. Thornton, K.P. McLaughlin, C.M. Tobalske, B.A. Maxell, D.P. Hendricks, C.R. Peterson, and R.L. Redmond. 1998.  Montana atlas of terrestrial vertebrates.  Montana Cooperative Wildlife Research Unit, University of Montana, Missoula, MT.  1302 p.
    • Hutto, R.L. and J.S. Young.  1999.  Habitat relationships of landbirds in the Northern Region, USDA Forest Service, Rocky Mountain Research Station RMRS-GTR-32.  72 p.
    • Maxell, B.A.  2000.  Management of Montana's amphibians: a review of factors that may present a risk to population viability and accounts on the identification, distribution, taxonomy, habitat use, natural history, and the status and conservation of individual species.  Report to U.S. Forest Service Region 1.  Missoula, MT: Wildlife Biology Program, University of Montana.  161 p.
    • Werner, J.K., B.A. Maxell, P. Hendricks, and D. Flath.  2004.  Amphibians and reptiles of Montana.  Missoula, MT: Mountain Press Publishing Company. 262 p.

Food Habits
Introduced adult bullfrog populations consume birds, rodents, frogs, snakes, turtles, lizards, and bats. Larvae are herbivorous on aquatic algae and plants and can have a significant impact upon benthic algae, and have the potential to disturb aquatic community structure. Adults are voracious eaters who will also prey on their own young. In Oklahoma, the diet in ponds was (percent by weight) predominantly insects (82) (mostly Coleoptera, Orthoptera, Hemiptera), and crayfish (6). In streams the diet was mostly crayfish (73) and insects (25) (mostly Coleoptera).

Found in lakes, ponds, cattle tanks, bogs, oxbow wetlands and sluggish portions of streams and rivers. They breed in late-June and July producing 10,000 to 20,000 eggs. Tadpoles transform to adults as quickly as 4 months in warmer climates and up to 3 years in colder locations. In colder climates, bullfrogs require year-round persistence of water for tadpoles to mature and over-winter. American Bullfrogs may be affecting R. pipiens and R. pretiosa populations in the Bitterroot Valley. Suitable ponds are now occupied solely by American Bullfrogs.

Reproductive Characteristics
In Montana, American Bullfrogs breed during warm weather in late-June and July. Females can produce 10,000 to 20,000 eggs. Eggs hatch in about 4 or 5 days. Tadpoles transform as quickly as 4 months in warmer climates and up to 3 years in colder locations. The tadpole stage may last 2-3 years in Montana based on Bitteroot and Yellowstone River studies. American Bullfrogs reach sexual maturity in 4 to 5 years. Eggs were observed in western Montana in early July. Tadpoles were observed metamorphosing into juvenile frogs in early June.

Current management for the Yellowstone River populations has been to try and eliminate as many populations as possible to prevent further spread. Not much management has taken place in the Bitterroot Valley where bullfrogs have virtually wiped out native amphibians from many of the low valley ponds and wetlands.

Contact information for Aquatic Invasive Species personnel:
Montana Fish, Wildlife, and Parks Aquatic Invasive Species staff.
Montana Department of Natural Resources and Conservation's Aquatic Invasive Species Grant Program.
Montana Invasive Species Council (MISC).
Upper Columbia Conservation Commission (UC3).

Threats or Limiting Factors
Desiccation or drying of the wetland habitats before tadpoles metamorphose to adults is the limiting factor to bullfrogs. Based on a study in western Washington, conservation of ephemeral wetlands will halt range expansions of bullfrogs. Permanently inundated wetlands and man-made ponds are more likely to house the non-indigenous amphibian.

  • Literature Cited AboveLegend:   View Online Publication
    • Flores Nava, A. 2018. Cultured Aquatic Species Information Programme. Rana catesbeiana (Shaw, 1862). Cultured Aquatic Species Information Programme. In: Food and Agriculture Organization of the United Nations Fisheries and Aquaculture Department [online]. Rome. Updated 9 February 2005. [Cited 15 August 2018].
    • National Research Council. 1974. Amphibians. Guidelines for the breeding, care and management of laboratory animals. National Academy of Sciences, Washington, D.C.162pp.
    • Sepulveda, A. J., M. Layhee, D. Stagliano, J. Chaffin, A. Begley, and B. Maxell. 2015. Invasion of American bullfrogs along the Yellowstone River. Aquatic Invasions. Volume 10, Issue 1: 69–77
    • Werner, J.K., B.A. Maxell, P. Hendricks and D.L. Flath. 2004. Amphibians and Reptiles of Montana. Mountain Press Publishing Company: Missoula, MT. 262 pp.
  • Additional ReferencesLegend:   View Online Publication
    Do you know of a citation we're missing?
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    • Werner, J.K. and J.D. Reichel. 1996. Amphibian and reptile monitoring/survey of the Kootenai National Forest: 1995. Montana Natural Heritage Program. Helena, MT. 115 pp.
    • Werner, J.K. and J.D. Reichel.  1994. Amphibian and reptile survey of the Kootenai National Forest: 1994. Montana Natural Heritage Program. Helena, MT. 104 p.
    • Werner, J.K. and T. Plummer. 1995. Amphibian and reptile survey of the Flathead Indian Reservation 1993-1994. Salish Kootenai College, Pablo, MT. 55 pp.
    • Werner, J.K. and T. Plummer. 1995. Amphibian monitoring program on the Flathead Indian Reservation 1995. Salish Kootenai College, Pablo, MT. 46 p.
    • Werner, J.K., T. Plummer, and J. Weaselhead. 1998b. The status of amphibians on the Flathead Reservation, Montana. Intermountain Journal of Sciences 4(3-4): 88.
    • Werner, J.K., T. Plummer, and J. Weaslehead. 1998. Amphibians and reptiles of the Flathead Indian Reservation. Intermountain Journal of Sciences 4(1-2): 33-49.
    • Werner, Y.L. 2003. Mechanical leverage in the middle ear of the American bullfrog, Rana catesbeiana. Hearing Research 175:54-65.
    • Western EcoTech, Helena, MT., 1999, Wetland delineation report for the Haskins Landing Proposed Wetland Mitigation Area. MWFE? June 2, 1999.
    • Wiese, R.J. 1985. Ecological aspects of the bullfrog in northeastern Colorado. M.S. Thesis, Colorado State University, Fort Collins, Colorado.
    • Wiese, R.J. 1990. Genetic structure of native and introduced populations of the bullfrog, a successful colonist. Ph.D. Dissertation, Colorado State University. Fort Collins, Colorado. 113 pp.
    • Wiewandt, T.A. 1969. Vocalization, aggressive behavior, and territoriality in the bullfrog, Rana catesbeiana. Copeia 1969(2): 276-285.
    • Wilcox, J.T. 2005. Rana catesbeiana (American Bullfrog). Diet. Herpetological Review 36:306.
    • Willis, Y.L., D.L. Moyle, and T.S. Baskett. 1956. Emergence, breeding, hibernation, movements and transformation of the bullfrog, Rana catesbeiana in Missouri. Copeia 1956(1): 30-41.
    • Willson, J.D. and M.E. Dorcas. 2004. A comparison of aquatic drift fences with traditional funnel trapping as a quatitative method for sampling amphibians. Herpetological Review 35(2):148-150.
    • Wollmuth, I.P. and I.I. Crawshaw. 1988. The effect of development and season on temperature selection in bullfrog tadpoles. Physiological Zoology 61: 461-469.
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Citation for data on this website:
American Bullfrog — Lithobates catesbeianus.  Montana Field Guide.  .  Retrieved on , from