CaliforniaHerps.com

A Guide to the Amphibians
and Reptiles of California


American Bullfrog - Lithobates catesbeianus

Shaw, 1802

(= Rana catesbeiana)
Click on a picture for a larger view



American Bullfrog California range map
Introduced Range: Red


Alien Herps in California


Listen to this frog:

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A short example



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This is an alien species that has been introduced into California. It is not a native species.

American Bullfrog American Bullfrog American Bullfrog American Bullfrog
  Large adult female, San Diego County   Large adult, with eye injury,
Imperial County
American Bullfrog American Bullfrog American Bullfrog American Bullfrog
  Adult female, Stanislaus County   Adult male, Los Angeles County
American Bullfrog American Bullfrog American Bullfrog American Bullfrog
Juvenile, Stanislaus County
Adult male, Merced County Juvenile, Merced County
American Bullfrog American Bullfrog American Bullfrog American Bullfrog
Large adult male, San Mateo County Juvenile, Fresno County © Jeff Ahrens Adult, Del Norte County
© Alan Barron
American Bullfrog American Bullfrog American Bullfrogs American Bullfrogs
Juvenile, Santa Barbara County © Jeff Ahrens Adults and juvenile, Kings County
© Patrick Briggs
Adult, San Francisco County
© Luke Talltree
American Bullfrog American Bullfrog American Bullfrog American Bullfrog
Very dark sub-adults, possibly melanistic, found in a Butte County pond.
© Roxanne Mulder
American Bullfrogs have large
webbed hind feet.
Comparison of adult American 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.
       
American Bullfrogs From Outside California
American Bullfrog American Bullfrog American Bullfrog American Bullfrog
Adult female, Benton Co., Oregon Adult female, Refugio County, Texas Sub-adult, Adams County, Washington Juvenile male, Benton Co., Oregon
American Bullfrog American Bullfrog American Bullfrog  
Male calling at night from a lake in
Santa Cruz County, Arizona.
Adult Female, Yavapai County, Arizona Skeleton of an adult American Bullfrog  
       
American Bullfrogs Feeding and Predation
American Bullfrog American Bullfrog Diablo Range Gartersnake Diablo Range Gartersnake
Adult bullfrog eating a lesser goldfinch that came to drink in an artificial pond in Tehama County. © Lori Grennan A Diablo Range Gartersnake eating a Bullfrog tadpole in Santa Clara County. The snake regurgitated the tadpole. © Chad Lane
American Bullfrog      
Bullfrog swallowing a goldfish it found in an artificial pond in Tehama County
© Bonnie Kieley
     
       
Tadpoles and Froglets
American Bullfrog Tadpole American Bullfrog Tadpole  
Mature tadpole, San Bernardino County Mature tadpole, Merced County  
American Bullfrog Juvenile American Bullfrog Juvenile American Bullfrog Juvenile  
Tailed metamorph, 1 day
after leaving the water
Tailed metamorph, 3 days
after leaving the water
Tailed metamorph, 5 days
after leaving the water
 

You can see more pictures of American Bullfrog tadpoles,
and their development into frogs here.

This Series Shows a Leucistic American Bullfrog Tadpole Found in Germany as it Changes Into a Frog Over a Period of 11 Months
All photos © Michael Waitzmann
American Bullfrog American Bullfrog American Bullfrog American Bullfrog
Aquatic tadpole, 8/30/16 Aquatic tadpole, 9/03/16 Tailed metamorphosed froglet, 9/17/16 Froglet, 10/09/16
American Bullfrog American Bullfrog American Bullfrog American Bullfrog
Juvenile frog, 06/23/17 Juvenile frog, 06/23/17 Juvenile frog, 07/16/17 Juvenile frog, 07/16/17
       
Habitat
American Bullfrog Habitat American Bullfrog Habitat American Bullfrog Habitat American Bullfrog Habitat
Habitat, San Joaquin River,
Fresno County
Habitat, city lake, Los Angeles County Desert agricultural irrigation pond habitat, Riverside County Habitat, Irrigation canal,
Imperial County
American Bullfrog Habitat American Bullfrog Habitat American Bullfrog Habitat American Bullfrog Habitat
Habitat, Yolo County canal Habitat, agricultural irrigation canal, Sacramento County Habitat, foothills creek, 500 ft.,
Stanislaus County
Habitat, large artificial reservoir,
Fresno County
American Bullfrog Habitat American Bullfrog Habitat American Bullfrog Habitat American Bullfrog Habitat
Habitat, large reservoir,
Contra Costa County
Habitat, pond, Marin County Tadpole habitat, Merced County
Habitat, creek, San Bernardino County
American Bullfrog Habitat American Bullfrog Habitat Red-eared Slider Habitat  
Habitat, Colorado River, Imperial County Habitat, pools at the edge of a river, Mendocino County Habitat, river, Sacramento County
© Noah Morales
 
       
Short Videos
American Bullfrog American Bullfrogs American Bullfrog American Bullfrogs
Views of several bullfrogs in ponds and creeks. Bullfrogs sitting around a crowded pond interact with each other, making chirping sounds and other noises. A bullfrog on the edge of a small pond tries to grab a bug with its tongue and fails, but succeeds on the second try, then jumps into the water to finish it off. Hundreds of bullfrogs make their frightened chirping sounds as they jump in and out of the water, or run across the surface to escape from danger.
American Bullfrog tadpoles      
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.      
       
Videos of Calling Male Bullfrogs
American Bullfrog American Bullfrog American Bullfrog
American Bullfrog
A big male bullfrog calls from the edge of a lake in the daytime. He sat making single calls every few minutes, until suddenly lots of other bullfrogs began calling all around him and then he made longer series of calls. Here we see him start with a full series of calls, then wait a bit before making a second series of calls, but this time starting with some longer notes before doing his typical calls. There was a second male about 10 feet from him who was silent, but after this male makes his second full series of calls, the second male begins calling at 1 minute 10 seconds into the video. We can't see him, but he is about as loud as the first frog. You hear him  when you can see that the first frog is silent. The second male's calling disturbed this frog so much, he made a short, sharp, territorial call and leaped in the air in the direction of the second frog. He landed closer to the second frog, but the second frog hadn't moved.
This is a very short version of the first series of calls heard in the long video shown on the left. This is also from the long video shown on the left - the short, sharp, territorial call made just before the frog leaps toward the other male. A large male Bullfrog calls at night from a lake in Santa Cruz County, Arizona.

More pictures of this frog and its natural habitat can be seen on our
Northwest Herps
page, and our Texas Herps page.



Description
 
Size
The largest native frog inhabiting North America.
Adults are 3.5 - 8 inches long from snout to vent (8.9 - 20.3 cm). (Stebbins, 2003)
Males grow up to 7.09 inches long (18 cm), females up to 8 inches long (20.3 cm).

Appearance
A large frog with long legs and large webbed toes.
Dorsolateral folds are not present.
A short fold extends from the eye over and past the eardrum to the forearm.
The tympanum is conspicuous.
Color and Pattern
Light green to dark olive green above, with dark spots and blotches. Sometimes light green only on the upper jaw.
Cream to yellow below with grey marbling on larger individuals.
Male/Female Differences
Males have tympanums larger than their eyes and a yellow throat.
The base of a male's thumb is swollen and dark.
A female's tympanum is about the size of her eye.
Young
Juveniles have many small dark spots.
Larvae (Tadpoles)
Tadpoles are greenish yellow with small spots, growing up to 6 in. (15.3 cm).

Life History and Behavior
Activity
American Bullfrogs are highly aquatic - rarely found far from water.
Active day and night.
Prefers a relatively high body temperature and becomes active later in the spring in colder areas.
In areas with freezes in winter, bullfrogs hibernate under water, buried in mud or laying on a pond bottom.
Movement
Adults and juveniles are capable of hopping large distances.
Bullfrogs are very strong swimmers.
Defense
When disturbed, they will hop into water and dive down, usually making a loud squeaking sound as they jump.
When captured they will sometimes play "possum" then suddenly jump away.

Bullfrogs and tadpoles are upalatable to many predators.
Territoriality
Males defend their territory from other males during the breeding season.
A territorial sound is often used.
Longevity
Longevity in the wild is thought to be 8-10 years, but captive specimens have lived nearly 16 years.
Voice (Listen)
The advertisement call is a loud low-pitched two-part drone or bellow, popularly described as "jug-o'rum." This is one of the loudest frog calls heard in California These calls are made during the day and at night.
Bullfrogs also produce an alarm call, a short fast squeak, which is usually made before the frog jumps into the water to escape from danger.
A short sharp "bonk" encounter call is also made.
A loud open-mouthed screaming sound is made when a frog is under extreme stress, such as when it is being attacked or eaten by a snake.

An older female will sometimes vocalize along with males to let her better choose the most dominant male.
Diet and Feeding
Eats anything it can swallow, including invertebrates, mammals, birds, fish, reptiles, and amphibians including other bullfrogs.

Bullfrogs typically sit and wait for food to come near them, then they lunge after it. It is likely that bullfrogs also actively hunt other frogs after hearing their breeding or distress calls.

Tadpoles eat algae, aquatic plant matter, and some invertebrates.
Breeding
Reproduction is aquatic.
Fertilization is external, with the male grasping the back of the female and releasing sperm as the female lays her eggs.

The reproductive cycle is similar to that of most North American Frogs and Toads. Mature adults come into breeding condition and the males call to advertise their fitness to competing males and to females. Males and females pair up in amplexus in the water where the female lays her eggs as the male fertilizes them externally. The eggs hatch into tadpoles which feed in the water and eventually grow four legs, lose their tails and emerge onto land where they disperse into the surrounding territory.

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.

Males set up a territory and make an advertisement call at night, but the call is also heard sometimes during the day.
Males defend their territory from other males.

Females choose a mate by entering a male's territory. An older female will also sometimes vocalize along with males, which creates more competition among the males, allowing the female to better choose the most dominant male.
Eggs
Older females are capable of laying two clutches of eggs in a year.
A female may lay as many as 20,000 eggs and lose up to 27 percent of her body weight.
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. Eggs hatch in 3 - 5 days.
Tadpoles and Young
Tadpoles prefer areas of warm shallow water with dense aquatic vegetation. Transformed froglets are 2 in. (5 cm.) in length.

Bullfrog tadpoles are noxious to many species of fish who eat them only as a last resord, and they are probably probably noxious to some reptiles, birds and mammals.

Tadpoles enter metamorphosis anywhere from a few months in the Southern US to the end of their 2nd or 3rd summer in Michigan. In most of California transformation probably occurs after the second summer. (This is a guess based on seeing many large tadpoles in California waters that appear to have lived at least a year.)

Habitat
Inhabits warm, sunny, open, permanent water - lakes, ponds, sloughs, reservoirs, marshes, slow river backwaters, irrigation canals, cattle tanks, and slow creeks. Found in grassland, farmland, prairies, woodland, chaparral, forests, foothills, and desert oases. Frequently inhabits artificial ponds and sometimes sealed swimming pools.

Geographical Range
Native Range

The species is native east of the Rocky Mountains throughout most of the midwestern, eastern and southern USA, reaching north barely into Canada, and south into eastern Mexico, 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 and Hawaii.


Global Range Introductions

American Bullfrogs have been introduced for food around the world. Some of the countries in which American Bullfrogs have been introduced include Mexico, Canada, Cuba, Jamaica, Dominican Republic, Puerto Rico, Italy, Greece, the Netherlands, France, Germany, Argentina, Brazil, Uruguay, Venezuela, Colombia, China, South Korea, and Japan.


Introduced Range in California

American Bullfrogs are found throughout most of California, but they are absent from dry deserts and high elevations in the Sierra Nevada Mountains.
Widespread on Catalina Island.

Bullfrogs appear to have been isolated in range in the 1920s, but spread quickly around the state afterwards.
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."
"done in the first instance by laymen intent upon adding a desirable species to our rather meager frog fauna..." which might be true, but they were also introduced so thier legs could be eaten.

According to Stebbins & McGinnis (2012) American Bullfrogs were first introduced into California either in 1896 or in 1905 (both dates are used in the book) in order to use their legs as a food source. Bullfrog legs are nearly twice as large as the legs of the native California Red-legged Frog that had previously been used for food, so frog hunters concentrated on catching the rapidly-expanding bullfrogs instead of red-legged frogs, but since red-legged frog legs were considered to have a much better taste than bullfrog legs, both frogs continued to be hunted.

According to Tracy I. Storer, in "The Eastern Bullfrog in California" (California Fish and Game Volume 8, Number 4, October 1922) the term "French frogs" was commonly used throughout California for any frog large enough to eat, including California Red-legged Frogs and American Bullfrogs.

Full Species Range Map
Red coloring on this map shows the Countries where American Bullfrogs have been introduced, not their exact range.

Full Species Range Map

Elevational Range
Found at elevations from near sea level to about 9,000 ft. (2,740 m) in Colorado. (Stebbins, 2003)

Notes on Taxonomy
In 2006, Frost et al divided North American frogs of the family Ranidae into two genera, Lithobates and Rana. Rana is still used in most existing references.


Alternate and Previous Names (Synonyms)

Rana catesbeina - American Bullfrog (Stebbins & McGinnis 2012)
Rana catesbeina
- Bullfrog (American Bullfrog) (Stebbins 2003)
Rana catesbeina - Bullfrog (Stebbins 1954, 1966, 1985)
Rana catesbeina
- Bullfrog (Bloody Nouns, Bully, Jug-o' Rum, North American Bullfrog, American Bullfrog) (Wright & Wright 1949)
Rana catesbeina
- Eastern Bullfrog (Storer 1925)
Rana catesbeina (Shaw 1802)

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. Bullfrog tadpoles are noxious to many species of fish which greatly increases their chance of survival. 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 (and maybe still are) common in the pet trade in California. Once they transform and growinto frogs, making their care requirements more complicated, 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.

A 2010 study of part of the Trinity River in California1 concluded that extensive human modifications of the river system have caused it to support American Bullfrogs to the detriment of native amphibian species, and that restoring the river to a more natural state should help to control the bullfrogs and improve conditions for native amphibians.

1 Fuller, T. E., Pope, K. L., Ashton, D. T. and Welsh, H. H. (2011), Linking the Distribution of an Invasive Amphibian (Rana catesbeiana) to Habitat Conditions in a Managed River System in Northern California. Restoration Ecology, 19:204213.

A 2009 study2 has documented male Rana draytonii in amplexus with juvenile American Bullfrogs and has proposed that this causes reproductive interference by the invasive species which could cause a reduction in the population growth rate of Rana draytonii since these males no longer call to attract females which causes fewer females to attempt to breed at the site, and because males engaged in amplexus are at greater risk of predation. And it raises the possibility that male Rana draytonii will find the smaller female Rana draytonii unattractive, leaving them without mates. This preference by the males leads them into an "evolutionary trap." 2 D'Amore, Antonia, Erik Kirby and Valentine Hemingway. Reproductive Interference By An Invasive Species: An Evolutionary Trap? Herpetological Conservation and Biology 4(3):325-330. Submitted: 2 September 2008; Accepted: 9 November 2009.
Taxonomy
Family Ranidae True Frogs Rafinesque, 1814
Genus Lithobates American Water Frogs Fitzinger, 1843
Species catesbeianus American Bullfrog

Shaw, 1802
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

Meaning of the Scientific Name
Lithobates - Greek - Litho = a stone, bates = one that walks or haunts
catesbeianus -
honors Catesby, Mark

Taken in part from Scientific and Common Names of the Reptiles and Amphibians of North America - Explained © Ellin Beltz

Related or Similar California Frogs
Lithobates berlandieri
Lithobates pipiens
Lithobates yavapaiensis
Rana draytonii
Rana aurora
Rana boylii
Rana cascadae
Rana pretiosa
Rana muscosa


More Information and References
California Department of Fish and Wildlife

AmphibiaWeb

Stebbins, Robert C., and McGinnis, Samuel M.  Field Guide to Amphibians and Reptiles of California: Revised Edition (California Natural History Guides) University of California Press, 2012.

Stebbins, Robert C. California Amphibians and Reptiles. The University of California Press, 1972.

Stebbins, Robert C. A Field Guide to Western Reptiles and Amphibians. 3rd Edition. Houghton Mifflin Company, 2003.

Behler, John L., and F. Wayne King. The Audubon Society Field Guide to North American Reptiles and Amphibians. Alfred A. Knopf, 1992.

Powell, Robert., Joseph T. Collins, and Errol D. Hooper Jr. A Key to Amphibians and Reptiles of the Continental United States and Canada. The University Press of Kansas, 1998.

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.

Robert Powell, Roger Conant, and Joseph T. Collins. Peterson Field Guide to Reptiles and Amphibians of Eastern and Central North America. Fourth Edition. Houghton Mifflin Harcourt, 2016.

Conant, Roger, and 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.

Storer, Tracy I. A Synopsis of the Amphibia of California. University of California Press Berkeley, California 1925.

Wright, Albert Hazen and Anna Wright. 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.

Conservation Status

The following status listings are copied from the 2017 Special Animals List and the 2017 Endangered and Threatened Animals List which are published by the California Department of Fish and Wildlife.

If no status is listed here, the animal is not included on either CDFW list. This most likely indicates that there are no serious conservation concerns for the animal. To find out more about an animal's status, you can go to the NatureServe and IUCN websites to check their rankings.

Check here to see the most current complete lists.


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.



Organization
Status Listing
NatureServe Global Ranking
NatureServe State Ranking
U.S. Endangered Species Act (ESA) None
California Endangered Species Act (CESA) None
California Department of Fish and Wildlife None
Bureau of Land Management None
USDA Forest Service None
IUCN
 

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