American Bullfrog
Lithobates catesbeianus
![[American Bullfrog]](/images/48ds.jpg)
Description
Physical
Our largest frog, adults can reach a size of 20cm (8in) (Stebbins 2003 pg 240) in length. Rear feet have extensive webbing. Lacks dorsolateral fold. Prominent tympanum (ear drum) with fold around it. Distinct humped back.
Color and Pattern
Mottled olive, green, or brown above. Belly predominantly white or cream often with light grey mottled spots on the bottom of the hind legs and sometimes belly. Lacks a face mask.
Sexual Dimorphism
Adult males usually have a yellow throat. The tympanum of adult males is much larger than the eye. In adult females, the tympanum is about the same size as the eye.
Habitat
Highly aquatic, needs permanent bodies of water to breed. Prefers ponds, lakes, and slower moving streams. They do not like too much vegetation on the edge of the bank, preferring habitat that allows them to bask.
Diet
While they do feed upon insects, they are opportunistic feeders and will prey upon anything that moves that they can fit into their mouth, including ducklings, birds, snakes, rodents, fish, tadpoles, and even other bullfrogs.
Distribution Range
General range map taken from CWHR.
Museum records taken from following institutions: CAS Herps, MVZ Herps.
Introduced. They are most commonly encountered in urban areas but have spread to many remote areas of the county.
Typical Elevation
We do not yet have enough records from distinct localities to calculate typical elevation. We need 14 more distinct localities.
Voice
The breeding call is a slow deep guttural g-r-r-u-u-u-u-m.
When alarmed, young bullfrogs often make a high pitched chirp when diving into the water.
Reproduction and Young
Most reproduction in our area seems to occur between late March and early Summer.
Eggs are laid in large masses 1 to 5 feet across and can contain more than 47,000 eggs. Eggs are laid on the surface of the breeding pool but soon sink to the bottom (Stebbins 2003 pg 445).
Tadpoles are a mottled olive green and quickly grow to a size larger than other native tadpoles. They are similar in appearance to California Red-legged Frog (Rana draytonii) tadpoles but lack pinkish bellies (Stebbins 2003 pg 461).
Tadpoles sometimes over-winter in our area, typically emerging in February or March. Transformation takes place typically from late July to September, freshly transformed frogs are about the size of a 50 cent piece and often leave the body of water where they were spawned in search of territory of their own. This behavior is one of the many reasons why it is a very bad idea to put tadpoles of this invasive species into a backyard pond.
Taxonomy
The American Bullfrog (Lithobates catesbeianus) was originally described in 1802 by Shaw as Rana catesbeiana. See Amphibian Species of the World.
There are no currently recognized subspecies.
Pronunciation
The assumed IPA pronunciation of this species: /lɪ θoʊ ˈbɑ teɪs/ /kæ tɛs bi ˈɒ nʌs/
Taxonomic Etymology
Lithobates is a combination of two Greek words. λίθος (Lithos) means gemstone or smooth stone. Bates is a derivation of the Greek verb βαίνω which means “to walk”.
catesbeianus honors Mark Catesby (Beltz 2006).
Taxonomy Notes
A study of new world representatives of the family Ranidae found five major clades (Hillis and Wilcox 2005 pg. 304). Four of the clades are closer related to each other than they are to the fifth, and make up a group known as Novirana. This group was elevated to genus status in 2006 by (Frost et al. 2006 pg. 10) taking the genus name Lithobates, though not without some controversy (Pauly, Hillis and Cannatella 2009 pg. 123).
Before this change, these frogs were classified in the genus Rana. As such, current literature often refers to this species as Rana catesbeiana.
Additional Information
Notes
The American Bullfrog is an invasive species that has caused considerable harm in Shasta County to our native species. The American Bullfrog was originally brought to California probably for food, but it may have also found its way to many locations as a result of tadpoles bought at pet stores and placed in backyard ponds and may also have spread as a result of tadpoles being transported with trout fingerlings.
Images
Unless otherwise noted, all images are of wild specimens in Shasta County.
Please be kind, do not hotlink images and do not use images without permission of the copyright owner.
![[American Bullfrog]](/images/24sm.jpg)
©Michael A. Peters
Adult Female. Redding, CA. Notice the fold around her left tympanum and the lack of a dorsolateral fold.
![[American Bullfrog]](/images/25sm.jpg)
![[American Bullfrog]](/images/43sm.jpg)
![[American Bullfrog]](/images/48sm.jpg)
![[American Bullfrog]](/images/49sm.jpg)
©Michael A. Peters
Notice the lack of any coloration in the groin area compared to our native Rana species. Small ditch adjacent to Sulfur Creek. Redding, CA
![[American Bullfrog]](/images/67sm.jpg)
©Michael A. Peters
The larger tadpole is probably a year older than the smaller tadpole. Both collected in Redding, CA
![[American Bullfrog]](/images/78sm.jpg)
©Michael A. Peters
Adult Male. Notice the very large tympanum compared to the eye size that gives the sex away. Pond in Golf Course along Benton Dr. Redding, CA.
![[American Bullfrog]](/images/88sm.jpg)
©Michael A. Peters
Young American Bullfrog in last stages of metamorphosis. Churn Creek near Twin View Blvd. Redding, CA
![[American Bullfrog]](/images/159sm.jpg)
©Michael A. Peters
Juvenile hanging out in aquatic vegetation. Clear Creek near China Garden Trail.
Habitat Shots
Unless otherwise noted, these habitat shots are from within Shasta County where this species is known to occur.
![[American Bullfrog habitat]](/images/45sm.jpg)
![[American Bullfrog habitat]](/images/68sm.jpg)
![[American Bullfrog habitat]](/images/158sm.jpg)
©Michael A. Peters
Several males were heard calling from the aquatic vegetation. Clear Creek near China Garden Trail.
Multimedia
Young adults in small pool. Camera allowed to run for 20 minutes, footage reduced to 2:41 minutes. Churn Creek, Redding, CA
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