Summary ⁶

The American bullfrog (Lithobates catesbeianus), often simply known as the bullfrog in Canada and the United States, is an aquatic frog, a member of the family Ranidae, or “true frogs”. This species has traditionally been classified as Rana catesbeiana, however the classification has been changed to Lithobates due to paraphyly in Ranidae. This frog has an olive green back and sides blotched with brownish markings and a whitish belly spotted with yellow or grey. The upper...

Description ⁷

This frog is the largest in North America and is distinguished by lacking dorsolateral folds and having very large tympanums, larger than the eye in males. The tips of the fingers and toes are blunt. The webbing is well developed. The skin on the back of this species is rough with random tiny tubercles. There is no dorsolateral fold, but there is a prominent supratympanic fold. The mean snout to vent length for males is 152 mm (range 111-178) and for females it is 162 mm (range 120-183). The males have pigmented nuptial pads. The vocal openings are at the corner of the mouth.The dorsum is green, with or without a netlike pattern of gray or brown on top. The venter is slightly white, sometimes mottled with gray or yellow. Coloration varies widely depending on the locality of the bullfrog (Conant and Collins 1975).

See another account at californiaherps.com.

Associations ⁸

Humans hunt bullfrogs for frog legs, but they have a limited hunting season in most states. Bullfrogs are also eaten by a wide variety of other animals, depending on the region. These include herons, such as great blue herons and great egrets, turtles, water snakes, raccoons, and belted kingfishers. Most fish are averse to eating bullfrog tadpoles because of their undesirable taste.

Known Predators:

• great blue herons (Ardea herodias)
• great egrets (Ardea alba)
• belted kingfishers (Megaceryle alcyon)
• turtles (Testudines)
• water snakes (Nerodia)
• raccoons (Procyon lotor)

Barcode data: rana catesbeiana ⁹

The following is a representative barcode sequence, the centroid of all available sequences for this species.


There are 14 barcode sequences available from BOLD and GenBank.

Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.

See the BOLD taxonomy browser for more complete information about this specimen and other sequences.

Behaviour ¹⁰

The call of a male bullfrog has a low frequency and can be heard for over one kilometer. The sound is often described as a low rumbling "jug-o-rum". Bullfrogs also have a good sense of vision and sense vibrations. See a video of a bullfrog calling here:   http://www.midwestfrogs.com/.

Communication Channels: acoustic

Perception Channels: visual ; tactile ; acoustic ; vibrations ; chemical

Communication and perception ¹¹

The call of a male bullfrog has a low frequency and can be heard for over one kilometer. The sound is often described as a low rumbling "jug-o-rum". Bullfrogs also have a good sense of vision and sense vibrations. See a video of a bullfrog calling here:   http://www.midwestfrogs.com/.

Communication Channels: acoustic

Perception Channels: visual ; tactile ; acoustic ; vibrations ; chemical

Conservation status ¹²

Bullfrogs do well with changes in the environment that have occured due to human modification, and are becoming increasingly common in areas modified by humans. Bullfrogs have a much higher critical thermal maximum than most other frogs, meaning that they are able to thrive in higher water temperatures. Bullfrogs have a longer breeding season and a higher rate of pre-metamorphic survivorship, which also allows them to be more successful than other frogs. In some areas, such as California, bullfrogs are driving other frog populations to extinction. One possible reason to explain why bullfrogs in California might have an advantage over other species native to that state is that bullfrogs evolved with a diverse predatory fish fauna in eastern North America. In California there have been attempts to control bullfrog populations by introducing new fish species that are their predators. Bullfrogs have evolved mechanisms to avoid predation by fish, such as less palatable eggs and tadpoles, and tadpoles that are not active much of the time, which reduces their exposure to predators. Native frog species of California are also suffering a decline because bullfrogs are efficient predators of frogs and tadpoles.

US Federal List: no special status

CITES: no special status

State of Michigan List: no special status

IUCN Red List of Threatened Species: least concern

Development ¹³

About four days after fertilization, spotted tadpoles emerge from the floating egg mass. The tadpoles have gills and a tail, which eventually disappears as the tadpole transforms into a froglet. Tadpole development is quite slow; it may take between one to three years to begin transformation from the tadpole stage into the adult stage. Adults reach sexual maturity after an additional two years.

Development - Life Cycle: metamorphosis

Distribution ¹⁴

North American bullfrogs (Lithobates catesbeianus) are only native to the Nearctic region. They are found from Nova Scotia to central Florida, from the East coast to Wisconsin, and across the Great Plains to the Rockies. The natural western limits of this species are now confused due to their introduction into places as far west as California and Mexico. It is known that bullfrogs were introduced to areas of California and Colorado in the early 1900's. The species has also been introduced (accidentally or on purpose) into southern Europe, South America, and Asia.

Biogeographic Regions: nearctic (Native ); palearctic (Introduced ); oriental (Introduced ); neotropical (Introduced )

Distribution and habitat ¹⁵

R. catesbeiana is widely distributed in eastern North America, ranging from Nova Scotia to central Florida and west to eastern Wyoming, Colorado and New Mexico. It occurs throughout most of Texas and into northwestern Mexico. It has been widely introduced for a variety of purposes, and is now common in many parts of western North America and many other countries, including those in Europe, Asia and South America (e.g., see Lever 2003). Rana catesbeiana is strongly aquatic, and can be found primarily at the edges of lakes, marshes, or cypress bays (Conant and Collins 1975).

Economic importance for humans: negative ¹⁶

Introduced bullfrogs may be driving native frogs to extinction in some areas. Colorado, among many other places, is experiencing problems due to the introduced bullfrog population. Bullfrogs may have been introduced accidentally to trout streams and lakes during the Colorado Divisions of Wildlife fish stocking operations. Bullfrogs occasionally invade fish hatchery ponds and their larvae are caught along with the fishes that are routinely stocked in ponds.

Economic importance for humans: positive ¹⁷

North American bullfrogs help to control insect pests. They are important for medical research because their skeletal, muscle, digestive, and nervous systems are similar to those of other animals. They are often hunted for meat (frog legs).

Positive Impacts: food ; research and education; controls pest population

Food habits ¹⁸

Bullfrogs are predators. They usually eat serpentes, Annelida, insecta, crustacea, anura, tadpoles, and aquatic eggs of actinopterygii, frogs, insects, or caudata. They are cannibalistic and will not hesitate to eat their own kind. There have also been a few cases reported of bullfrogs eating chiroptera. Bullfrog tadpoles mostly graze on aquatic plants.

Animal Foods: birds; mammals; amphibians; reptiles; fish; eggs; insects; terrestrial non-insect arthropods; mollusks; terrestrial worms; aquatic crustaceans

Plant Foods: algae

Geographic range ¹⁹

North American bullfrogs (Rana_catesbeiana) are only native to the Nearctic region. They are found from Nova Scotia to central Florida, from the East coast to Wisconsin, and across the Great Plains to the Rockies. The natural western limits of this species are now confused due to their introduction into places as far west as California and Mexico. It is known that bullfrogs were introduced to areas of California and Colorado in the early 1900's. The species has also been introduced (accidentally or on purpose) into southern Europe, South America, and Asia.

Biogeographic Regions: nearctic (Native ); palearctic (Introduced ); oriental (Introduced ); neotropical (Introduced )

Habitat ²⁰

North American bullfrogs must live in water and are therefore usually found near some source of water, such as a lake, pond, river, or bog. Warm, still, shallow waters are preferred. Bullfrogs are becoming increasingly common in areas that have been modified by humans. Increased water temperatures and increased aquatic vegetation, which are common factors of lakes polluted by humans, favor bullfrogs by providing suitable habitats for growth, reproduction, and escape from predators.

Habitat Regions: temperate ; freshwater

Aquatic Biomes: lakes and ponds; rivers and streams

Wetlands: marsh ; swamp ; bog

Known prey organisms ²¹

Rana catesbeiana preys on:
Chelydra serpentina
Diadophis punctatus
Anas fulvigula
Bombycilla cedrorum
Parascalops breweri

This list may not be complete but is based on published studies.

Life cycle ²²

About four days after fertilization, spotted tadpoles emerge from the floating egg mass. The tadpoles have gills and a tail, which eventually disappears as the tadpole transforms into a froglet. Tadpole development is quite slow; it may take between one to three years to begin transformation from the tadpole stage into the adult stage. Adults reach sexual maturity after an additional two years.

Development - Life Cycle: metamorphosis

Life expectancy ²³

The average bullfrog lives seven to nine years in the wild. The record lifespan of an animal in captivity is 16 years.

Range lifespan
Status: captivity: 16 (high) years.

Typical lifespan
Status: wild: 7 to 9 years.

Average lifespan
Status: wild: 7-9 years.

Average lifespan
Sex: male
Status: captivity: 6.6 years.

Average lifespan
Status: captivity: 8.0 years.

Average lifespan
Status: captivity: 16.0 years.

Life history, abundance, activity, and special behaviors ²⁴

The breeding season begins in spring and lasts throughout early summer, but can vary according to latitude. Bullfrogs breed on the surface of shallow, permanent water covered with vegetation. Males make distinctive resonant low-pitched calls with a single note that lasts 0.8 seconds at a frequency of 1.0 kHz. Males also display aggressive territorial behavior in defending good oviposition sites. One clutch consists of up to 20,000 eggs and one quarter of the female's body weight. Duration of the larval stage varies greatly depending on the temperature. Metamorphosis is not synchronized.Bullfrogs are often the predominant species in interspecific relationships, contributing to the decline of other amphibians and excluding them from the habitat. Bullfrog juveniles are adept at colonizing new ponds, and they are believed to disperse throughout an environment this way. Bullfrogs are opportunistic predators, and prey on any animal smaller than themselves. While smaller bullfrogs eat mostly insects, larger bullfrogs consume aquatic species such as fish and crayfish, mice, and other frogs (for a video, see the account on Bufo californicus). Cannibalism is prevalent in a bullfrog's diet, sometimes comprising up to 80% of its food.

For additional details on Life History, please refer to the Lannoo account (click on yellow tab above).

Life history, abundance, activity, and special behaviors ²⁵

Introduced populations present great threats to native frogs, due to the bullfrog's voracious feeding habits and the size and competitive ability of the larvae. Although aquatic species and frogs constitute a major portion of its diet, other native species are also likely affected because bullfrogs have been reported to eat snake, birds, and small mammals as well. Furthermore, as bullfrogs are being introduced worldwide, they serve as carriers of the pathogenic fungus Batrachochytrium dendrobatidis (chytrid), which causes the lethal disease chytridiomycosis, believed to be a major factor in recent global amphibian declines (e.g., Garner et al. 2006 found that bullfrogs were consistently chytrid-infected in multiple countries). Infected bullfrogs appear to be rather resistant to chytridiomycosis, whereas the disease is lethal to many other amphibians, making the bullfrog an efficient carrier of the chytrid fungus (Daszak et al. 2004).Argentina: Introduced populations of R. catesbeiana have been recently reported in San Juan (Sanabria et al. 2005), Misiones (Pereyra et al. 2006), Buenos Aires (Barrasso et al. 2009), and Córdoba and Salta provinces (Akmentins and Cardozo 2009). Most introductions come from intentional or incidental releases from breeding facilities, except for Misiones where the bullfrogs there are believed to be the result of the range expansion of a Brazilian population (Pereyra et al. 2006). The bullfrog's adaptive ability has allowed it to invade a diversity of environments and disperse throughout Argentina. It has been observed to prey on native vertebrates. Although it has not yet been identified as a chytrid carrier in Argentina, its negative influence as a potential disease carrier remains to be further examined. One Argentinian species greatly affected by the presence of R. catesbeiana is Leptodactylus ocellatus, a generalist predator who shares a similar diet with R. catesbeiana and whose larvae are being preyed on by bullfrogs (Barrasso et al. 2009). The increase in number of captive-breeding facilities due to a large demand for human consumption and the lack of effective governmental control thereof are serious concerns in Argentina (Akmentins and Cardozo 2009).Belgium: Bullfrog larvae have been imported on a large scale for trade in pet shops. Many specimens were released into the wild and were able to survive to reach adulthood (Stumpel 1992). Free-ranging populations of R. catesbeiana have been observed in Belgium (Ficetola et al. 2006). Conservationists are concerned about the potential threat of R. catesbeiana to indigenous species, in particular Rana esculenta, which occupies the same niche (Stumpel 1992).Brazil: Introductions date as early as the 1930's in association with aquaculture. Except for the coldest months of the year, R. catesbeiana reproduces continuously during warm weather such as that of Brazil (Kaefer et al. 2007). This characteristic is shared with the cane toad (Bufo marinus, another invasive species in Brazil. The degree of native population loss brought on by the introduction of bullfrogs is still being speculated, but the reproductive ability of R. catesbeiana is worrisome. Giovanelli et al. (2008) propose that the Brazilian Atlantic Forest biodiversity hotspot in southern and southeastern Brazil may be the most susceptible to invasion, based on ecological niche modeling. Furthermore, a chytridiomycosis outbreak in an Uruguayan farm with stock that originated from Brazil suggests that Brazilian rearing facilities may contain specimens that are infected by B. dendrobatidis, and could thus be harmful to native anuran species if allowed to escape (Mazzoni et al. 2003). These authors urge the Brazilian government to regulate human introductions of R. catesbeiana more strictly.China: R. catesbeiana was first introduced to China in 1959. Since then, breeding populations have been established in most provinces of mainland China including Yunnan, Sichuan, Shanxi, and Zhejian Provinces (Wang et al. 2007). The bullfrog has been widely bred for both local consumption and for export since the 1980s (Wu et al. 2005). Escapes occur from rearing pens or in the process of transportation or trade (Wu et al. 2005; Li et al. 2006; Liu and Li 2009). R. catesbeiana poses a great threat to native anuran species due to its voracious feeding habits. Its body size is also much larger than any other native species, and it is known to consume at least 4 of the 10 native species in the Zhoushan archipelago of Zhejian Province. Wang et al. (2007) quantified the predatory impacts of R. catesbeiana and found that body size plays an important role in predator-prey interactions with native anurans of China. It has been suggested that the primary threat posed by juvenile bullfrogs is food competition, whereas the primary threat posed by adult bullfrogs is predation (Wu et al. 2005). Chytridiomycosis has also been reported from introduced bullfrogs (wild, farmed, and market-sold) in Yunnan province, as well as in native amphibians, suggesting that farmed and escaped bullfrogs may present a major threat to native species by carrying disease as well (Bai et al. 2010).Colombia: R. catesbeiana was introduced into Colombia in the 1990s and inhabits the inter-Andean valleys (Lynch 2006a). The bullfrog was originally introduced in hopes of exploiting it for food consumption, but it is now a biological plague in the valley of the Río Cauca and in certain localities on the western slopes of the Cordillera Oriental in Cundinamarca, as well as the lowlands of the Caribbean Region (Lynch 2006b). Its diet in Colombia has been reported to consist mostly of insects (56%), whereas vertebrates constitute only 2% of the diet (Daza and Castro 1999). Many endogenous Colombian frog species have been impacted by the lethal fungal disease chytridiomycosis; R. catesbeiana is a potential vector in Colombia of the fungal pathogen Batrachochytrium dendrobatidis (Ruiz and Rueda-Almonacid 2008).Cuba: In the 1920s, both adult and larval bullfrogs were observed in two small ponds near Rincon, a small village approximately 50 kilometers from Havana. It was not deemed a threat to the ecological system in Cuba at that time because it was thought that the bullfrog, which had a larval period of more than one year, would not be able to breed in the many temporary pools in Cuba (Hoffman and Nobel 1927). Now, bullfrogs are present throughout Cuba except the Sierra del Cristal National Park (Fa et al. 2002).France: Acclimatized R. catesbeiana populations have been recorded in France beginning in the 1960s (Ficetola et al. 2006). It was observed to be occurring near Bordeaux in 1997, in a limited area of gravel pits (Neveu et al. 1997). Currently, southwest France is the European area where the strongest expansion of R. catesbeiana is taking place; it also represents the second largest area in Europe where R. catesbeiana is present, constituting about 2,000 square km. Only three breeding populations have been reported, but observations of isolated individuals suggest that translocations are frequent. These secondary translocations facilitated by humans can substantially increase the rate of population expansion, which may further enhance capture and translocation. A large-scale eradication plan is being carried out in southwest France, including trapping of both adults and tadpoles, and education of local people (Ficetola et al. 2006). Unfortunately, samples of introduced populations of bullfrogs in Loir et Cher are found to be infected with B. dendrobatidis (Garner et al. 2006).Italy: R. catesbeiana was introduced to Italy in the 1930s, making it the first European country where this species was successfully introduced (Ficetola 2006). It is well established in northern Italy and breeds abundantly. Provinces affected at least since 1960 include Mantova, Pavia, and Verona (Lanza 1962). In northern Italy, the R. catesbeiana population does not appear to have expanded since the 1980's. Some populations are known to be infected by B. dendrobatidis (Ficetola 2006).Jamaica: Twenty-two R. catesbeiana specimens were first introduced to the Great Morass of the Black River of Jamaica in 1967 for commercial purposes. During the next 4 years it has spread in all directions from the point of introduction and eventually established themselves in the Upper Morass. Although no quantitative population estimates have been conducted, R. catesbeiana appears to have established extensive populations at suitable habitat areas of the island. Its expansion in Jamaica is further facilitated by temperature and lack of competition; the frogs breed continually throughout the year and displace local anurans such as Bufo marinus through habitat competition (Mahon and Aiken 1977).Japan: R. catesbeiana was first introduced to Japan by a professor at the Imperial University of Tokyo (now Tokyo University) around 1918 (Okada 1927). The frog was already well integrated into the Japanese herpetofauna by 1958-1959, approximately 40 years after its introduction (Telford 1960). R. catesbeiana is firmly established in at least the Kanto and Kansai Plains, the two largest lowland regions of Japan, and many local people recognize it as the "food frog" (Telford 1960). R. catesbeiana resides in freshwater habitats such as rice fields, ponds, and rivers. Studies reveal that it may negatively affect native anuran species such as the endangered Rana porosa brevipoda through predation and food competition. The removal of bullfrogs, along with other invasive exotic species, is highly recommended for conservation of local vertebrates (Hirai 2004). Studies reveal R. catesbeiana populations expanding in paddy fields prefer microhabitat with deep water; managing habitats to reduce immigration of bullfrogs may help prevent the spread of this invasive species (Minowa et al. 2008). A recent die-off of R. catesbeiana from ranavirus lasted from September through October 2008 in a 1000-m² pond in western Japan. Infected feral populations of R. catesbeiana presents a serious threat to Japanese amphibians (Une et al. 2009). Fortunately, B. dendrobatidis does not seem to have infected introduced populations of R. catesbeiana, and no die-off from chytridiomycosis has been reported (Garner et al. 2006).Netherlands: bullfrogs were imported for trade in pet shops in the 1980s. Many specimens are released into the wild as larvae or freshly metamorphosed juveniles. In 1991, a reproducing population since 1989 was recorded in a garden pond in the city of Breda (Stumpel 1992). Eradication programs have been carried out in the Netherlands (Scalera 2007).Puerto Rico: in 1935, the Insular Department of Agriculture and Commerce of Puerto Rico introduced a total of 40 R. catesbeiana specimens from Florida to a specially constructed pond at Rio Piedras. The population expanded successfully, and by 1951 had invaded the neighboring towns of Mayaguez and Humacao. It did not appear to prey on other amphibians, but did consume a diversity of local insects (Perez 1951).Taiwan: the species was introduced into Taiwan from the United States via Japan in 1924 and 1951 (Hsu et al. 1970). The country actively participates in the production of bullfrog meat, and in fact is the world's top exporter of ranids. However, its native amphibians are at risk of infection by B. dendrobatidis. Taiwan's subtropical climate also creates a suitable environment for the growth of this pathogen (Schloegel et al. 2009).Uruguay: R. catesbeiana was first introduced in 1987 for farming purposes, but at present most of the farms have closed down. A feral population was reported in 2008 at one of the closed farms at Rincón de Pando. Establishment of the population appears to be at an early stage but is potentially dangerous, as the invaded pond exhibits significant differences from non-invaded ones. For example, R. catesbeiana seems to have some type of positive interaction with fish, because the body size of common fish species are higher in the invaded pond where aquatic vertebrate richness is also highest. Furthermore, R. catesbeiana is the highest fraction of vertebrate biomass, displacing native amphibian species such as Hypsiboas pulchellus. Other negative effects on local amphibian fitness include reducing the premetamorphic period due to competition and predation pressures. The high level of anthropogenic disturbance and large amount of suitable habitat in Uruguay may facilitate R. catesbeiana expansion (Laufer et al. 2008). Recent mass deaths occurred at a large farming facility for bullfrogs 46 km from Montevideo, Uruguay, and the cause is suspected to be chytridiomycosis (Mazzoni et al. 2003). This is potentially dangerous to native anurans if R. catesbeiana were to serve as a carrier of B. dendrobatidis. However, no control program was implemented for these closed farms. Laufer et al. (2008) recommend taking measures against the population expansion as well as searching for new invasion points.Venezuela: the bullfrog was introduced as a food source around the 1990s, and has established dense populations in 14 natural and artificial ponds as far as 4.3 km away from the point of introduction. Examination of R. catesbeiana specimens in the Venezuelan Andes suggests that the bullfrog acts as a pathogen carrier that causes amphibian population declines in Venezuela (Hanselmann et al. 2004). 79.9% of the bullfrogs surveyed are infected with B. dendrobatidis and carrying an average of 2299 zoospores (Sánchez et al. 2008). Of the infected frogs, 96% appear otherwise healthy, making R. catesbeiana an efficient reservoir host. It is likely that year-round bullfrog breeding will heighten the impact of chytridiomycosis (Hanselmann et al. 2004). Chytridiomycosis is detected in native species occuring in pond, stream and terrestrial habitats from 80-2600 m. Dendropsophus meridensis, an endangered native species sympatric with R. catesbeiana, shows the highest infection prevalence and mean zoospore load (26.7% and 2749 zoospores). Although no clinical signs of disease were detected, environmental stress could potentially increase its vulnerability to the pathogen (Sánchez et al. 2008). B. dendrobatidis is also known to migrate through autoclaved late water to reach distant amphibian populations outside the range of R. catesbeiana dispersal (Hanselmann et al. 2004).R. catesbeiana has been introduced worldwide, and AmphibiaWeb is in the process of editing the Trends and Threats section of this page for each country.

Morphology ²⁶

North American bullfrogs are the largest true frog found in North America, weighing up to 0.5 kg and 203 mm in length. Typical length ranges from 90 to 152 mm. Color varies from brownish to shades of green, often with spots or blotches of a darker color about the back. The hind feet are fully webbed. The sex of an adult bullfrog can be easily determined by examining the size of the tympanum (the external ear of the frog) relative to that of the eye. The tympanum is a round circle located on the side of the head near the eye, and in males it is much larger than the eye. In females the tympanum is as large or smaller than the eye. Also, during the breeding season the throat of the male bullfrog is yellow, whereas the female's is white.

Range mass: 0.5 (high) kg.

Range length: 460 (high) mm.

Average length: 100-175 mm.

Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry

Sexual Dimorphism: sexes shaped differently

Average basal metabolic rate: 0.0134 W.

National nature serve conservation status ²⁷

Canada

United States

Physical description ²⁸

Bullfrogs are the largest real frog found in North America, weighing up to 0.5 kg and measuring 460 mm in length. Their average length is 100-175 mm. Their color varies from brownish to shades of green, often with spots or blotches of a darker color around their backs. Their back feet are fully webbed. The sex of an adult bullfrog can be found out easily by examining the size of the tympanum (the external ear of the frog) relative to size of the eye. The tympanum is a round circle located on the side of the head near the eye, and in males it is much larger than the eye. In females the tympanum is as large or smaller than the eye. Also, during the breeding season the throat of the male bullfrog is yellow, and the female's is white.

Range mass: 0.5 (high) kg.

Range length: 460 (high) mm.

Average length: 100-175 mm.

Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry

Sexual Dimorphism: sexes shaped differently

Predation ²⁹

Humans hunt bullfrogs for frog legs, but they have a limited hunting season in most states. Bullfrogs are also eaten by a wide variety of other animals, depending on the region. These include ardeidae, such as Ardea herodias and Ardea alba, testudines, Nerodia, procyon lotor, and Ceryle alcyon. Most fish are averse to eating bullfrog tadpoles because of their undesirable taste.

Known Predators:

• great blue herons (Ardea_herodias)
• great egrets (Ardea_alba)
• belted kingfishers (Ceryle_alcyon)
• turtles (Testudines)
• water snakes (Nerodia)
• raccoons (Procyon_lotor)

Relation to humans ³⁰

This large frog is widely farmed for human consumption as a source of meat, as well as for entertainment or as an agent to control pest population (Lever 2003).

Reproduction ³¹

Mating System: polygynous

Breeding takes place in May to July in the north, and from February to October in the south. Fertilization is external, with the females depositing as many as 20,000 eggs in a foamy film in quiet, protected waters. Fertilization is usually, but not always, by one male. Tadpoles emerge about four days after fertilization. These tadpoles may remain in the tadpole stage for almost 3 years before transforming into frogs. Adults reach sexual maturity after 3 to 5 years.

Breeding interval: Bullfrogs breed once each year.

Breeding season: May to July in the north and February to October in the south

Range number of offspring: 20000 (high) .

Average time to hatching: 4 days.

Range age at sexual or reproductive maturity (female): 3 to 5 years.

Range age at sexual or reproductive maturity (male): 3 to 5 years.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (External ); oviparous

Females provide the eggs with yolk before they are laid. There is no parental involvement in offspring after the eggs are laid. Newly hatched tadpoles can take care of themselves right away.

Parental Investment: pre-fertilization (Provisioning, Protecting: Female)

Sources and Credits

1. (c) Denis Doucet, some rights reserved (CC BY-NC), uploaded by Denis Doucet
2. (c) cyric, some rights reserved (CC BY-NC-SA), uploaded by cyric
3. (c) Gabriel Kamener, some rights reserved (CC BY-NC-SA), http://farm3.static.flickr.com/2444/3624958681_3f7e79b8ca.jpg
4. (c) 2010 William Flaxington, some rights reserved (CC BY-NC), http://calphotos.berkeley.edu/cgi/img_query?seq_num=187426&one=T
5. (c) Carl D. Howe, some rights reserved (CC BY-SA), https://upload.wikimedia.org/wikipedia/commons/thumb/a/aa/North-American-bullfrog1.jpg/460px-North-American-bullfrog1.jpg
6. Adapted by Denis Doucet from a work by (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Lithobates_catesbeianus
7. Adapted by Denis Doucet from a work by (c) AmphibiaWeb © 2000-2015 The Regents of the University of California, some rights reserved (CC BY), http://eol.org/data_objects/34272021
8. (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31402763
9. (c) Barcode of Life Data Systems, some rights reserved (CC BY), http://eol.org/data_objects/30593028
10. (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31402761
11. (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/25066647
12. (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31402766
13. Adapted by Denis Doucet from a work by (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/25066644
14. Adapted by Denis Doucet from a work by (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31402755
15. Adapted by Denis Doucet from a work by (c) AmphibiaWeb © 2000-2011 The Regents of the University of California, some rights reserved (CC BY), http://eol.org/data_objects/23855286
16. Adapted by Denis Doucet from a work by (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/25066651
17. Adapted by Denis Doucet from a work by (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/25066650
18. Adapted by Denis Doucet from a work by (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/25066648
19. Adapted by Denis Doucet from a work by (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/25066641
20. Adapted by Denis Doucet from a work by (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31402756
21. Adapted by Denis Doucet from a work by (c) SPIRE project, some rights reserved (CC BY), http://eol.org/data_objects/10526715
22. Adapted by Denis Doucet from a work by (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31402758
23. Adapted by Denis Doucet from a work by (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31402760
24. Adapted by Denis Doucet from a work by (c) AmphibiaWeb © 2000-2011 The Regents of the University of California, some rights reserved (CC BY), http://eol.org/data_objects/23855287
25. Adapted by Denis Doucet from a work by (c) AmphibiaWeb © 2000-2011 The Regents of the University of California, some rights reserved (CC BY), http://eol.org/data_objects/23855288
26. Adapted by Denis Doucet from a work by (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31402757
27. Adapted by Denis Doucet from a work by (c) NatureServe, some rights reserved (CC BY-NC), http://eol.org/data_objects/28740331
28. Adapted by Denis Doucet from a work by (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/25066643
29. Adapted by Denis Doucet from a work by (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/25066649
30. Adapted by Denis Doucet from a work by (c) AmphibiaWeb © 2000-2011 The Regents of the University of California, some rights reserved (CC BY), http://eol.org/data_objects/23855289
31. Adapted by Denis Doucet from a work by (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31402759

More Info

• iNaturalist.ca taxon page
• AMNH Amphibian Species of the World
• AmphibiaWeb
• Animal Diversity Web
• Biodiversity Heritage Library
• BOLD Systems BIN search
• CalPhotos
• Global Biodiversity Information Facility (GBIF)
• HerpMapper
• Maryland Biodiversity Project
• NatureServe Explorer 2.0
• NBN Atlas
• Ninnescah Life
• VertNet
• 日本のレッドデータ検索システム

Range Map

(c) Barcode of Life Data Systems, some rights reserved (CC-BY)

iNaturalist.ca Map