In these places they are considered an invasive species due to their voracious appetite and the large number of eggs they produce, which has a negative effect on native amphibians, certain insects and other fauna.

[5][6][7][8] The nuclear genome[9] (~5.8Gbp) of the North American bullfrog (Rana [Lithobates] catesbeiana) was published in 2017[10] and provides a resource for future Ranidae research.

[11] The dorsal (upper) surface of the bullfrog has an olive-green basal color, either plain or with mottling and banding of grayish brown.

They grow fast in the first eight months of life, typically increasing in weight from 5 to 175 g (0.18 to 6.17 oz),[15] and large, mature individuals can weigh up to 500 g (1.1 lb).

The bullfrog is originally native to eastern North America, where it is commonly found in every U.S. state east of the Mississippi River.

[18] The bullfrog has also been introduced onto Nantucket island, as well as portions of the western U.S., including Arizona, Colorado, Hawaii, Idaho, Nevada, New Mexico, Oregon, Utah, Washington and Wyoming.

[18] The bullfrog has been introduced in Hawaii, South America, Asia, the Caribbean, and Europe for various purposes including frog farming and population control of other species.

[22] Other countries and regions into which the bullfrog has been introduced include the extreme south of British Columbia, Canada, nearly every state in Mexico, as well as Belgium, Cuba, the Dominican Republic, Haiti, Italy, Jamaica, the Netherlands, and Puerto Rico.

[24][25] The reasons for introducing the bullfrog to these areas have largely been intentional, either to provide humans with a source of food[26] or as biological control agents.

In addition to the unintended escape of frogs from breeding establishments or scientific research facilities, captive escapees or released pets are also a possibility.

[23] Conservationists are concerned that the bullfrog is relatively immune to the fungal infection chytridiomycosis (also called 'chytrid' fungus) which has been ravaging numerous frog species, and, as it invades new territories, it may assist in the spread of this lethal fungus as an asymptomatic carrier to the more susceptible, native species of frog it encounters.

[28][29] A study of bullfrogs in Michigan showed the males arriving at the breeding site in late May or early June, and remaining in the area into July.

Though The reproductive cycle of American bullfrogs in Oregon is mainly restricted to the summer season when individuals congregate in lentic freshwater systems.

Males are present at the breeding pond for longer periods than females during the entire season, increasing their chances of multiple matings.

[37] The significance of forelimb sexual dimorphism allow males to remain in amplexus with the female for longer durations increasing their chance at reproductive success in the highly competitive mating environment.

[28] A review of multiple studies on bullfrogs and other anurans noted male behavior within the groups changes according to the population density of the leks.

[39] Chorus tenure is restricted due to increased risk of predation,[40] lost foraging opportunities,[41] and higher energy consumption.

[32] The New Jersey study noted the males would approach each other to within a few centimeters and then tilt back their heads, displaying their brilliantly colored gular sacs.

The New Jersey study also reported low posture with only the head exposed above the water surface was typical of subordinate, or non-territorial males, and females.

High posture was demonstrated by territorial males, which floated on the surface of the water with their lungs inflated, displaying their yellow gulars.

The female chooses a site in shallow water among vegetation, and lays a batch of up to 20,000 eggs, and the male simultaneously releases sperm, resulting in external fertilization.

They pump water through their gills by movements of the floor of their mouths, trapping bacteria, single-celled algae, protozoans, pollen grains, and other small particles on mucus in a filtration organ in their pharynges.

[51] Bullfrogs are able to capture large, strong prey because of the powerful grip of their jaws after the initial ranid tongue strike.

[52] The bullfrog is able to make allowance for light refraction at the water-air interface by striking at a position posterior to the target's perceived location.

In laboratory observations, bullfrogs taking mice usually swam underwater with prey in mouth, apparently with the advantageous result of altering the mouse's defense from counter-attack to struggling for air.

[54] Bullfrogs are an important item of prey to many birds (especially large herons), North American river otters (Lontra canadensis), predatory fish, and occasionally other amphibians.

[55][56] The eggs and larvae are unpalatable to many salamanders and fish, but the high levels of activity of the tadpoles may make them more noticeable to a predator not deterred by their unpleasant taste.

[62] This means that this species cannot under any circumstances be imported, bred, transported, commercialized, or intentionally released into the environment in the whole of the European Union.

[63] Self-sustaining populations of American bullfrogs became established in the United Kingdom around 1999, where their introduction was likely due to accidental escapes and deliberate releases from captivity.

[49] Countries that export bullfrog legs include the Netherlands, Belgium, Mexico, Bangladesh, Japan, China, Taiwan, and Indonesia.