Bullfrog

Amphibians are tetrapod animals that are ectothermic and belong to the class Amphibia. Lissamphibia is the name given to all live amphibians. They live in a wide range of environments, with the majority of species inhabiting terrestrial, fossorial, arboreal, or freshwater aquatic settings. Let us discuss the bullfrog meaning, the bullfrog is a category of frog that prefers vast, permanent bodies of water, such as marshes, ponds, and lakes as their habitat. Bullfrogs can be found in pools, koi ponds, canals, ditches, and culverts, among other places. The bullfrog receives its name from the bullfrog sound that the male produces during the breeding season, which sounds like a bull. The bullfrog is a huge frog that is extensively eaten across its range, particularly in the southern United States, where they are abundant.

Bullfrogs have spread over the world as a result of their availability as a food source. Bullfrogs have been brought to Western North America, South America, Western Europe, China, Japan, and Southeast Asia. They are invasive species in these areas due to their ravenous hunger and high number of eggs they generate, which harms native amphibians and other animals. Bullfrogs are extremely wary of humans, making capture difficult. As a result, they frequently establish themselves.

Types of Bullfrog

• Kaloula pulchra, a Southeast Asian banded bullfrog.

• Hoplobatrachus rugulosus, often known as the East Asian Bullfrog, is a Chinese edible frog that may be found in China and Southeast Asia.

• Jerdon's bullfrog, Hoplobatrachus crassus, was discovered in India.

• Hoplobatrachus tigerinus, often known as the Indus Valley bullfrog and yellow bullfrog, is a species of frog found in Pakistan and North India. This frog is also known as indian bull frog.

Images of Different Types of Bullfrog

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Morphological Features of the Bullfrog

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The bullfrog's dorsal (top) surface is olive-green in colour, either plain or with greyish brown mottling and banding. Off-white with yellow or grey blotches on the ventral (under) surface. The green top lip and the pale lower lip are frequently observed in stark contrast. 

The teeth are very small and are only used for gripping. Brown irises and horizontal, almond-shaped pupils make the eyes stand out. Just below the eyes, the tympana (eardrums) are visible, and the dorsolateral folds of skin stop close to them. Gray blotches or bands might be seen on the limbs. The forelegs are small and strong, while the hindlegs are long and slender. With the exception of the fourth toe, which is unwebbed, the front toes are not webbed, however the back toes have webbing between the digits.

Bullfrog Size

Male bullfrogs are smaller than females and have yellow throats, making them sexually dimorphic. Females' tympana are about the same size as their eyes, whereas males' tympana are larger than their eyes. Bullfrogs have a snout–to–vent length of around 3.6 to 6 in (9 to 15 cm). They grow quickly in the first eight months of life, gaining between 5 and 175 g (0.18 and 6.17 oz) of weight, and large, mature individuals can weigh up to 500 g. Bullfrogs have been documented weighing up to 800 grammes and measuring up to 8 inches (20 cm) from snout to vent. The American bullfrog is North America's largest frog.

Distribution 

Eastern North America is home to the bullfrog. Its native range is from the Atlantic Coast to Newfoundland in the north, and as far west as Oklahoma and Kansas in the west. It is absent from Florida, Colorado, Nebraska, South Dakota, and Minnesota, and is not found on offshore islands near Cape Cod. Nantucket Island, Arizona, Utah, other portions of Colorado and Nebraska, Nevada, California, Oregon, Washington, and Hawaii have all been exposed to it. It is classified an invasive species in several states, and there is fear that it may outcompete native amphibian species, disrupting the ecological balance. It's quite widespread on the West Coast, particularly in California, where it's thought to be a threat to the California red-legged frog and a role in the endangered species' decline.

Breeding Behaviour

Bullfrog breeding season lasts two to three months on average. Male bullfrogs arrived at the breeding site in late May or early June, according to a research in Michigan, and stayed until July. Territorial males who occupy sites are normally 3 to 6 m (9.8 to 19.7 ft) apart and make a lot of noise. Male bullfrogs have been seen making at least three different sorts of sounds in various situations. Territorial cries made as a threat to other males, marketing calls designed to attract females, and encounter calls made before conflict are all examples of these unique calls.

Bullfrogs have a long breeding season, during which the males are constantly engaged in sexual activity. Males spend more time at the breeding pond than females over the course of the season, increasing their chances of numerous matings. Males often have a higher sex ratio than females. Females, on the other hand, have brief periods of sexual receptivity throughout the season. Female sexual activity lasted on average one night in one research, and mating did not occur unless the females initiated physical contact. Females are only clasped by males when they have expressed their desire to mate. This study disproves prior statements that a male frog will grasp any nearby female regardless of whether she consents.

Male-to-male competition is considerable within the bullfrog population as a result of these male and female behaviours, and sexual selection for females is fierce. The most likely classifications for the bullfrog mating system, according to Kentwood Wells, are leks, territorial polygyny, and harems. Males assemble to attract females, while females arrive for the purpose of copulation, therefore leks would be a good description. The mating strategy of bullfrogs in New Jersey was classed as resource-defense polygyny in a 1980 research. Within the group, the men protected territory and displayed normal physical modes of protection.

Choruses

Choruses are groups of male bullfrogs that congregate. The male chorus activity is similar to how birds, mammals, and other vertebrates establish leks. Choruses are dynamic, establishing and remaining associated for a few days before disbanding and emerging again in a new area with a new group of males. Male movement has been observed to be dynamic in studies. The choruses were regarded as "centres of attraction" in the Michigan study, with their increased numbers enhancing the males' total sonic presentations. This is more appealing to ladies, as well as to other sexually active men.Choruses in this study were dynamic, forming and disbanding on a regular basis. Other parts of the site spawned new choruses. Within the choruses, males moved about a lot and were quite mobile.

Male behaviour within groups vary according to the population density of the leks, according to a study of much research on bullfrogs and other anurans. Due to the difficulty of defending individual territories among a large population of males, leks are preferred at greater population densities. Females choose their partners differently as a result of this variation. Female choice is largely controlled by territory quality when male population density is low and men maintain clearer, more distinct territories. Females rely on additional indications to choose their mates when male population density is higher. These indicators include, among other things, the men' locations in the chorus and variances in male display behaviours. Challenges, threats, and other physical displays are used to establish social authority within the choruses. Younger males are relegated to the perimeter, whereas older guys acquire more centre spots.

Aggressive Behaviour

Bullfrogs use many forms of violence, particularly visual displays, to gain social dominance within choruses. The importance of posture in establishing social position and frightening rivals cannot be overstated. Non-territorial males remain in the water with only their heads visible, whereas territorial males have inflated postures. The yellow-colored necks of dominant (territorial) males are visible due to their raised stance. When two dominant males come into contact, a wrestling match ensues. The males have their venters clenched and are standing erect, much above the water's surface. The males would approach each other to within a few millimetres of each other, then bend their heads back, revealing their brilliantly coloured gular sacs, according to the New Jersey study. Bullfrogs' gulars are dichromatic, with dominant and fitter males having yellow gulars. Low posture with only the head visible above the water surface was also shown to be typical of subordinate, or non-territorial males and females in the New Jersey study. Territorial males displayed high posture by floating on the water's surface with their lungs enlarged and displaying their yellow gulars. 

Males can improve their reproductive health in a variety of ways. Males maintain dominant, or territorial, status within the chorus in a variety of ways, including early arrival at the breeding site, prolonged breeding with continuous sexual activity throughout the season, ownership of a centrally located territory within the chorus, and successful movement between the dynamically changing choruses. Males who are older have more success in all of these areas than males who are younger. Many scholars refer to some males as having a more inferior function, which they refer to as the silent male status. These silent guys sit close to resident males in a submissive stance and make no attempt to remove them. The silent males do not try to seduce females; instead, they wait for territories to become available. This is also known as the satellite or alternate male method.

Growth and Development

The female chooses a male and then lays her eggs in his territory. The male rides on top of the female during the mating grab, or amplexus, and grasps her right behind her forelimbs. The female selects a location in shallow water among plants to lay a batch of up to 20,000 eggs, while the male releases sperm at the same time, resulting in external fertilisation. The eggs produce a thin, floating sheet that can cover 0.5 to 1.0 m2 (5.4 to 10.8 sq ft). The embryos grow best in water between 24 and 30 degrees Celsius (75 and 86 degrees Fahrenheit) and hatch in three to five days. 

When the water temperature goes above 32 degrees Celsius (90 degrees Fahrenheit), developmental problems emerge, and when it dips below 15 degrees Celsius (59 degrees Fahrenheit), normal development terminates. Tadpoles that have just hatched prefer to live in shallow water on fine gravel substrates. This could be due to the fact that there are less predators in these areas. They tend to travel into deeper water as they mature. 

Tadpoles have three pairs of external gills and multiple rows of labial teeth when they first emerge. They use the floor of their mouths to pump water through their gills, catching bacteria, single-celled algae, protozoans, pollen grains, and other minute particles on mucus in their pharynges' filtration organ. As they get older, they start ingesting larger particles and rasping with their teeth. They have deep bodies, downward-facing mouths, and wide dorsal and ventral fins on their tails.

The time it takes for a fish to metamorphose varies from a few months in the south to three years in the north, where the colder water inhibits development. The average longevity of a frog in the wild is 8 to 10 years, yet one frog in captivity lasted for over 16 years.

Relation of the Bullfrog with its Environment

Many birds (especially large herons), North American river otters (Lontra canadensis), predatory fish, and occasionally other amphibians prey on bullfrogs. Once they reach adulthood, predators of American bullfrogs can range from 150 g belted kingfishers (Megaceryle alcyon) to 1,100 pound (500 kg) American alligators (Alligator mississippiensis). Many salamanders and fish dislike the eggs and larvae, but the tadpoles' high levels of activity may make them more visible to a predator who isn't put off by their bad taste. Bullfrogs are hunted as game and their legs are eaten by humans. 

Adult frogs splash and leap into deep water to try to get away. Squawking or emitting a piercing scream by a cornered person may be enough to fool the assailant and allow the frog to flee. When one bullfrog is attacked, other bullfrogs in the area are likely to become aware of the danger and flee to deeper water. Bullfrogs may be partially immune to the venom of copperhead (Agkistrodon contortrix) and cottonmouth (Agkistrodon piscivorus) snakes, despite the fact that these species, like northern water snakes, are known natural predators of bullfrogs (Nerodia sipedon).

Multiple features within the L. catesbeianus contribute to its competitive ability, which is important given its invasive tendency. The American bullfrog's generalist diet allows it to eat in a variety of settings. Adult bullfrogs often ingest predators of bullfrog young, such as dragonfly nymphs, garter snakes, and gigantic water beetles, according to the contents of American bullfrog stomachs. As a result, the ecological check on juvenile American bullfrogs in invaded areas is less effective. L. catesbeianus appears to have immunity or resistance to antipredator defences found in other organisms. 

The stomach contents of bullfrog populations in New Mexico revealed that wasps are regularly consumed, with no conditioned avoidance due to the wasps' stingers. The stomach contents of L. catesbeianus found along the Colorado River show that it can tolerate the stickleback fish's venomous spines. There have also been reports of American bullfrogs eating scorpions and rattlesnakes.

Analysis of the realised niche of the American bullfrog at various locations in Mexico, as well as comparisons with the niches of endemic frogs, show that the American bullfrog is capable of niche shift, posing a threat to many endemic Mexican frog species, including those that are not currently in competition with the American bullfrog.

Did You Know

• Bullfrogs are utilised for dissection in science classes as well as for food. Bullfrog tadpoles are commonly sold at ponds and fish stores, and albino bullfrogs are sometimes kept as pets.

• Tadpoles of the Indian bull frog are carnivorous and consume other tadpoles.