Introduced Range: Red
Listen to this frog:
A short example
More sounds of
Rana catesbeiana
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Introduced: not native to California
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Adult female, Stanislaus County |
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Juvenile, Stanislaus County
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Large adult, with eye injury, Imperial County |
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Adult male, Merced County |
Juvenile, Merced County |
Large adult male, San Mateo County |
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Comparison of adult Bullfrog tympanums (the round eardrum behind the eye). The diameter of an adult male's tympanum (left) is larger than the diameter of the eye. The diameter of an adult female's tympanum (right) is smaller than or equal to the diameter of the eye. |
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Adult female, Benton Co., Oregon |
Juvenile male, Benton Co., Oregon |
Sub-adult, Adams County, Washington |
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Male calling at night from a lake. |
Adult Female, Yavapai County, Arizona |
Tadpole, Merced County
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More pictures of tadpoles, and their development can be viewed here.
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Habitat |
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Habitat, San Joaquin River, Fresno County
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Habitat, pools at the edge of a river, Mendocino County |
Desert agricultural irrigation pond habitat, Riverside County |
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Habitat, Yolo County canal |
Habitat, agricultural irrigation canal, Sacramento County |
Habitat, foothills creek, 500 ft., Stanislaus County |
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Habitat, large reservoir,
Contra Costa County
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Habitat, pond, Marin County |
Habitat, large artificial reservoir, Fresno County |
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Habitat, Colorado River, Imperial County |
Tadpole habitat, Merced County
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Habitat, creek, San Bernardino County |
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Habitat, Irrigation canal,
Imperial County
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Short Video |
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| Views of several bullfrogs in ponds and creeks. |
Although they are quick to swim to the bottom when first approached, American Bullfrog tadpoles will usually calm down and resuface, where they slowly swim, float, and socialize. |
A large male Bullfrog calls at night from a lake.
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Description |
| Size |
The largest true frog inhabiting California.
Adults are 3.5 - 8 in. long from snout to vent (5.7 - 11.4 cm). Males grow up to 7 1/8 in. (18 cm), females up to 8 in. (11.4 cm). |
| Appearance |
A large frog, light green to dark olive green above, with dark spots and blotches. Juveniles have many small dark spots. Sometimes light green only on the upper jaw. Cream to yellow below with grey marbling on larger individuals. No dorsolateral folds. A short fold extends from the eye over and past the eardrum to the forearm. Conspicuous tympanum. Males have tympanums larger than their eyes and a yellow throat.
Tadpoles are greenish yellow with small spots, growing up to 6 in. (15.3 cm). |
| Voice (Listen) |
| A loud low-pitched two-part drone or bellow, popularly described as "jug-o'rum." These calls are made during the day and at night. Bullfrogs also produce an alarm call, a fast squeak, which is usually made before the frog jumps into the water to escape from danger. A sharp encounter call is also made, and a loud open-mouthed screaming sound is made when a frog is under extreme stress. |
| Behavior |
Highly aquatic. Rarely found far from water. Active day and night. When startled, usually emits a chirp or squeak, then jumps into the water. Prefers a relatively high body temperature and becomes active later in the spring in some areas. In areas with freezes in winter, bullfrogs hibernate under water buried in mud or laying on a pond bottom. Longevity in the wild is thought to be 8-10 years, but captive specimens have lived nearly 16 years.
Bullfrogs and tadpoles are upalatable to many predators. Adults and juveniles are capable of hopping large distances, and when disturbed, they will hop into water and dive down, usually making a loud squeaking sound as they jump. |
| Diet |
Eats anything it can swallow, including invertebrates, mammals, birds, fish, reptiles, and amphibians including other bullfrogs. Bullfrogs sit and wait for food to come near them, then they lunge after it. It is likely that bullfrogs hunt and eat other frogs after hearing their breeding or distress calls.
Tadpoles eat algae, aquatic plant matter, and some invertebrates. |
| Reproduction and Young |
Reproduction is aquatic. Fertilization is external. Mating and egg laying occurs mostly from May to late August (but in some areas it occurs as early as March and as late as October.) Reproduction begins when the air temperature reaches a certain level (measured at one location in Kansas at 21 degrees C., or about 70 degrees F.)
Males are reproductively mature in 1-2 years, females in 2-3 years.
Older females are capable of laying two clutches of eggs in a year. Males set up a territory and make an advertisement call at night, but the call is also heard sometimes during daylight. Males defend their territory from other males. Females choose a mate by entering a male's territory. An older female will also vocalize sometimes along with males, which creates more competition among the males, allowing the female to further choose the most dominant male.
Eggs are laid in a sheet of jelly about 2 feet in diameter. The egg mass floats at first, then sinks to underwater vegetation just before hatching. A female may lay as many as 20,000 eggs and lose up to 27 percent of her body weight. Eggs hatch in 3 - 5 days.
Tadpoles enter metamorphosis anywhere from a few months in the South to the end of their 2nd or 3rd summer in Michigan. In most of California, transformation probably
occurs after the second summer. (This is just a guess based on seeing many large tadpoles in California waters that appear to have lived at least a year.) Tadpoles prefer areas of warm shallow water with dense aquatic vegetation. Transformed froglets are 2 in. (5 cm.) in length. |
| Range |
American Bullfrogs are found throughout most of California, but they are absent from dry deserts and high elevations in the Sierra Nevada Mountains.
The species is native throughout most of the midwestern, eastern and southern USA, reaching north barely into Canada, and south just below the Rio Grande River in Texas, and west to New Mexico and Colorado. The exact natural range of this species cannot be accurately determined because by the 1920's it had been introduced to frog farms outside of its natural range in order to use its large meaty legs for food, and escaped bullfrogs have become established throughout most of the western United States and southwestern Canada. (It has also been introduced for food around the world, in Hawaii, Mexico, Europe, Asia, South America, the Carribean Islands, Brazil, and Cuba.)
According to Storer (1925) "The Bullfrogs introduced into California have come from at least three sources. Those in Sonoma County were obtained from a dealer in New Orleans and presumably came from Louisiana; those introduced at Farmington were obtained in Missouri, while the frogs at Standard are said to have been obtained from a San Francisco dealer who purchased his stock in Hawaii."
He also states that the introduction of the Bullfrog in California was "done in the first instance by laymen intent upon adding a desirable species to our rather meager frog fauna..." |
| Habitat |
| Inhabits warm, sunny, open, permanent water - lakes, ponds, sloughs, reservoirs, marshes, slow river backwaters, irrigation canals, and slow creeks. Found in grassland, farmland, prairies, woodland, chaparral, forests, foothills, and desert oases. |
| Taxonomic Notes |
| This frog has been renamed Lithobates catesbeianus, but this nomenclature is not yet standard. |
| Conservation Issues (Conservation Status) |
The non-native American Bullfrog is probably responsible for some of the decline of many native species, including frogs, turtles, snakes, and waterfowl, which cannot compete with it or fall prey to it. Since bullfrogs evolved in habitats with a diverse number of predatory fish, unlike many California frog species, they probably have a competive advantage over native amphibians in areas where non-native fish are present. Bullfrogs also do well in areas disturbed by humans and in artificial wetland habitats such as farm and golf course ponds, unlike most native California frogs. Further introduction to waters where they are not present, should be prohibited and methods of eradication from waters where bullfrogs coexist with native amphibians should be studied and implemented if feasible. Bullfrog tadpoles were also once common in the pet trade, and may still be. Once they transform and grow into frogs, changing their care requirements, many of them are probably released into the wild.
In their native range, bullfrogs are experiencing some decline with habitat loss, habitat alteration, chemical contamination, and over-harvesting for food. |
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Taxonomy |
| Family |
Ranidae |
True Frogs |
| Genus |
Rana |
True Frogs |
| Species |
catesbeiana |
American Bullfrog
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Original Description |
Shaw, 1802 - Gen. Zool., Vol. 3, Pt. 1, p. 106, pl. 33
from Original Description Citations for the Reptiles and Amphibians of North America © Ellin Beltz
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Meaning of the Scientific Name |
Rana - Frog - "Rana" probably mimics how the Romans heard their call.
catesbeiana - honors Catesby, Mark
from Scientific and Common Names of the Reptiles and Amphibians of North America - Explained © Ellin Beltz
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Alternate Names |
Bullfrog
Lithobates catesbeianus
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Related or Similar California Frogs |
Rana draytonii
Rana aurora
Rana boylii
Rana cascadae
Rana pretiosa
Rana sierrae
Rana yavapaiensis
Rana pipiens
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More Information and References |
Natureserve Explorer
California Dept. of Fish and Game
AmphibiaWeb
Stebbins, Robert C. A Field Guide to Western Reptiles and Amphibians. 3rd Edition. Houghton Mifflin Company, 2003.
Behler, John L., & F. Wayne King. The Audubon Society Field Guide to North American Reptiles and Amphibians. Alfred A. Knopf, 1992.
Corkran, Charlotte & Chris Thoms. Amphibians of Oregon, Washington, and British Columbia. Lone Pine Publishing, 1996.
Jones, Lawrence L. C. , William P. Leonard, Deanna H. Olson, editors. Amphibians of the Pacific Northwest. Seattle Audubon Society, 2005.
Leonard et. al. Amphibians of Washington and Oregon. Seattle Audubon Society, 1993.
Nussbaum, R. A., E. D. Brodie Jr., and R. M. Storm. Amphibians and Reptiles of the Pacific Northwest. Moscow, Idaho: University Press of Idaho, 1983.
Conant, Roger, & Joseph T. Collins. A Field Guide to Reptiles and Amphibians Eastern and Central North America.
Third Edition, Houghton Mifflin Company, 1998.
Bartlett, R. D. & Patricia P. Bartlett. Guide and Reference to the Amphibians of Western North America (North of Mexico) and Hawaii. University Press of Florida, 2009.
Elliott, Lang, Carl Gerhardt, and Carlos Davidson. Frogs and Toads of North America, a Comprehensive Guide to their Identification, Behavior, and Calls. Houghton Mifflin Harcourt, 2009.
Lannoo, Michael (Editor). Amphibian Declines: The Conservation Status of United States Species. University of California Press, June 2005.
Wright, Anna. Handbook of Frogs and Toads of the United States and Canada. Cornell University Press, 1949.
Storer, Tracy I. A Synopsis of the Amphibia of California. University of Califonia Publications in Zoology Volume 27, The University of California Press, 1925.
Davidson, Carlos. Booklet to the CD Frog and Toad Calls of the Pacific Coast - Vanishing Voices. Cornell Laboratory of Ornithology, 1995.
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The following status listings come from the Special Animals List which is published several times each year by the California Department of Fish and Game.
This frog is not included on the Special Animals List, meaning there are no significant conservation concerns for it in California according to the California Department of Fish and Game.
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Organization
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Status Listing
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| U.S. Endangered Species Act (ESA) |
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| California Endangered Species Act (CESA) |
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| California Department of Fish and Game |
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| Bureau of Land Management |
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| USDA Forest Service |
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| Natureserve Global Conservation Status Ranks |
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World Conservation Union - IUCN Red List
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