Chordate Report

Chordate Report

Introduction

Invasive species are a risk to native wildlife. It is estimated that nearly 42% of global animals are threatened or are endangered species due to the risk of invasive species. An invasive species can range from amphibians, plants, insects, fish, bacteria, or fungi[1]. The influence of an invasive species is the harm it causes to the environment, the economy, and human health. Among these invasive species is the American bullfrog. Studies show the American bullfrog is an invasive species suspected to cause great ecological damage across the world. The interest of the present paper is to discuss the America bullfrog succinctly with a focus on the biological and ecological aspects of the species. The report will delineate the specific research process incorporated in studying the American bullfrog and its biological nature in addition to the impact on human life.

The American Bullfrog: Individual Interest

The American bullfrog is an animal of interest to me. The reason is due to the biological nature of the growth of this animal compared to other species within the same family category. North American bullfrogs have teeth in the roof of their mouth and a muscular tongue capable of flipping prey into their mouth. Accordingly, the American bullfrog is estimated to grow at a length of 8 inches or more and can weigh up to 1.5 pounds[2]. The estimation is also a marvel to its young stage development, the tadpole. The animal at the tadpole stage is estimated to reach 6.75 inches in length.  The standard size of an amphibian frog is between 6 to 9 inches, which is smaller compared to the American bullfrog[3]. Also, the American bullfrog is edible and is used as a human delicacy around the world. In some cases, it is used for fish bait, the pet trade, and pond landscapers. Another interesting fact about the American bullfrog is that it can adapt to any environment, and it is a relatively large, voracious and indiscriminate predator that can dominate any territory[4]. For this reason, it is known as an invasive species as it can compete with native anurans[5]. For instance, it is known that adult American bullfrogs are responsible for predation against aquatic herpetofauna, including snakes and turtles. On the other hand, with regard to human ecological relations, the frog is known to spread pathogens such as chytrid fungus, Batrachochytrium dendrobatidis, and R. catebeiana[6].

Interactions with Humans

Historically, between the 19^th and 20^th centuries, documentation state that translocation of the American bullfrog occurred from the United States to other parts of the world, including Canada, the Caribbean, Western Europe, and the rest of the world such as Asia. Humans, therefore, are known to consume the American bullfrog as a delicacy[7]. Due to other reasons such as the spread of fungus and is an invasive species, the American bullfrog is used for aesthetic purposes such as backyard ponds. Being an invasive species, the American bullfrog is known to take over public and manmade ponds, farm ponds, golf course ponds, reservoirs, and irrigation networks. The ability to do this is based on their adaptation to novel environments. Hence, it is common to fins American bullfrogs in urban and semi-urban areas.

Methods

the present report was conducted using credible sources regarding the American bullfrog. The search for the American bullfrog included search engines, Google. Based on google search, the researcher was able to retrieve at least 1, 000 sources from the search results. However, narrowing down the sources to be used, the researcher included the year of publication specific to the American bullfrog. The sources used are as follows:

CABI. Invasive Species Compendium. [Internet]; 2020. Available from https://www.cabi.org/isc/datasheet/66618

Roach, John. Invading Bullfrogs Appear Nearly Unstoppable. [Internet}. National Geographic; 2004. Available from https://www.nationalgeographic.com/animals/2004/09/news-bullfrogs-invading-nearly-unstoppable/

Louette G, Devisscher S, Adriaens T. Control of invasive American bullfrog Lithobates catesbeianus in small shallow water bodies. European Journal of Wildlife Research;  2013 Feb 1;59(1):105-14.

USGS. Nonindigenous Aquatic Species. [Internet]. 2020. Available from https://nas.er.usgs.gov/queries/FactSheet.aspx?SpeciesID=71

Results

1. Name

The common name for the frog is the American bullfrog, bullfrog, Rana toro, Rana toro American, and ran mugidora (Spanish).

• The Scientific Name

The scientific name of the American bullfrog is Rana catesbaeiana.

• Correct the non-scientific name of the animal.

The correct non-scientific name of the American bullfrog is the North American bullfrog.

2. Location on Earth

The initial location of the American bullfrog was in California in 1898. From this location, the frog leap is estimated to have spread all over the world primarily through human contact, and species need to invade other territories[8].

• The native range of the species

The American bullfrog is native to eastern North America. It is also estimated to range naturally from Nova Scotia, southern Quebec, and Ontario in Canada[9]. Other areas include the eastern United States and the Mississippi drainage down southward along the east coast of Mexico.

• Extended range of this species

The extended range of the species includes Hawaii, parts of western America, Canada, Mexico, and the Caribbean. Other areas include South America, Europe, and Asia. However, studies indicate that it is difficult in some areas to determine whether the species is native or invasive. For instance, the occurrence in the Rocky Mountains- It is believed the species may have been translocated to the region during the 19^th and early 20^th centuries[10].

• Specific habitats of the species

Ideally, the American bullfrog can colonize a wide range of lakes, reservoirs, ponds, irrigation ditches, marshes, and man-made ponds. However, permanent water is ideal for the American bullfrog, especially the tadpoles[11]. The tadpoles may take up to 12 months to mature and as long as 48 months to reach metamorphosis[12]. To do so, the tadpoles can also survive in intermittent ponds that can also be seasonal. These habitats can also be ideal for the mature bullfrogs for migration purposes, which is not ideal for successful reproduction. With respect to water temperature, American bullfrogs require warm water in the summer temperatures not to exceed 25 degrees Celsius[13]. This temperature is good for reproductive purposes. Other habitat requirements include lakes and ponds neither that are nor more than 6 meters deep and should have good sun-exposure around the margins, which ideal for reproduction as well[14].

For the riparian thickets, the abundance of aquatic and emergent vegetation are among the factors ideal for habitation. The reason is that they provide cover and are likely to provide diversity for species invasion. For instance, golf course ponds are ideal due to the provision of riparian plants that support the healthy bullfrog populace. On the other hand, the acidification of waterways is also associated with the American bullfrog. The acidification can cause a decline in population, especially instances such as the Southern Ontario region, which have high acidification levels, which limit the tolerance of the species to the water extremes.

In summary, the ideal habitats include terrestrial and freshwater. For terrestrial, they are riverbanks and wetlands. For freshwater, they are irrigation channels, lakes, reservoirs, rivers or streams, and ponds.   For the freshwater habitat, the American bullfrog is known to be harmful due to the introduction of pests or being an invasive species.

• The density of the species per acre in designated places

The species thrive in low densities with estimated > 780 adults per hectare. As for the tadpoles, the estimated population is 2 000 per acre.

• Conservation Status in the WDCAE, U.S., and Earth

As noted, the American bullfrog is an invasive species. The need to control its spreading population is among the campaigns both in America and the rest of the world. Given that the species lacks a prominent predator, has a prolific nature and incentive to relocate, it makes the American bullfrog difficult to eradicate. Inherently, there is no single identified method that can be used and is effective in eliminating them[15]. A number of habitat alteration methods have been effective in the past. It includes the killing of the adults, trapping and frightening the tadpoles, and using rotenone and other toxic chemicals applied in ponds to kill the tadpoles. In Buenos Aires, for instance, scientists successfully control bullfrogs through the capture of the adult bullfrogs that attempt to escape and kill them[16]. In Asia, on the other hand, the frogs are a delicacy. Large ponds and reservoirs are designated for their growth and later sale for human consumption.

3. Species Sizes

The estimated North American bullfrogs can grow between the length of 8 inches or more and can weigh up to 1.5 pounds. As for the tadpoles, it is estimated that the species can reach 6.75 inches in length, which is higher than other anuran species[17].

• Adult females

There are considered to be more aggressive compared to males. The tympanic membrane in the females is about the same diameter as their eyes[18]. The chins of the female frogs are more uniform compared to the males and are exceptionally white. They are also considered to be generally bigger than males.

• Adult Males

The American bullfrog’s males are larger, more muscular, and vocal compared to the females. They are distinguished by their tympanic membrane that covers their ears. They are also bigger in diameter compared to females. The males have a loud basso profundo mating call compared to the females, which can be heard during the mating season. Mating occurs between April and October.

• Immature sizes

The tadpoles can grow to up to 6 inches long.

4. Foods
   • Kinds and Frequency of Use of Each Kind of Food

Bullfrog tadpoles consume aquatic plants, including suspended matter, organic debris, algae, plant tissue, and other small aquatic invertebrates.

At the maturity stage or metamorphosis, American bullfrogs are carnivorous. For this reason, the consume animals both vertebrate and invertebrate, which can be captured and swallowed, including tadpoles and juveniles of their species[19]. They will consume from fish, tadpoles, snails, small reptiles, insects, rodents, birds, and bats[20]. The frequency of consumption is based on the invasiveness of the species in a specific habitat.

• Time of Year Species Consumes Each Kind of Food.

During mating, American bullfrogs are known to consume fish and other aquatic animals during the July and August periods. Non-native species are consumed less during this period a majority of the time, and the adult bullfrogs spend time in the water.

5. Reproduction
   • Kind of a mating system

American bullfrogs reach sexual maturity after two years. Breeding males attract females through their vocalizations. Polygyny is their main type of mating system[21]. The male positions itself on the female’s back and grasps her with the forearms around the anterior thorax and axillary region. The positioning is known as axillary amplexus, where the male nuptial pads contain roughened skin on the outer edges of the thumbs, which aid in holding onto the slippery females. During spawning, the interaction between released eggs and sperm occur[22].

• Mating season

The breeding season for the American bullfrog is between two to three months. Breeding occurs between late May and early June but can last as far as July. The male bullfrogs can occupy a territory of about 3 to 6 meters apart. It is defined, according to studies, that at least three different mating calls can be heard during this period. The calls can range from calling of other females; encounter calls to precede combat and threats to other males. The male sexual peak is longer compared to females.

• Clutches and litters

A female can lay up to 20 000 eggs and as low as 10 000 eggs.

• Size of egg clusters

The effs are very small, dark, and coated in proteins which immediately bond with water molecules to provide a protective jelly filled with water-filled egg capsule[23]. The eggs can range from a small watermelon to over I meter across.

• Time of egg clutches

It is estimated that the eggs can take between four to five days.

• Time of new adults

The hatched tadpoles can take up to 2 years to reach maturity. Each tadpole is estimated to be 4 to 6 inches in length[24].

• Time to develop from an egg

Tadpoles take at least two years to develop into a full-grown bullfrog. During this period, the eggs develop into an embryo and are best described to survive in water temperatures between 24 to 30 degrees Celsius. The newly hatched tadpoles then reside in shallow water or on fine gravel bottoms. The reason is due to the lesser number of predators in the area. The metamorphosis time takes between a few months to three years[25]. The location differs. In the southern region, American bullfrogs take up a few months to reach adulthood, whereas those in the north take up three years for maturity.

• Adult stages

The American bullfrog has four distinct lifecycle stages. These are egg, tadpole, froglet, and adult. A froglet is a smaller version of the full-grown bullfrog but, has a tail. As it develops, it loses its tail and develops lung[26]. The transition is in preparation to becoming a land animal. As for the adult stage, the bullfrog can survive in both land and water. At this stage, it can leap and reproduce. It is estimated that the lifespan of a full-grown bullfrog is between eight to ten years but can live as long as 16 years in captivity.

6. Characteristics of habitat

American bullfrogs colonize areas such as lakes, reservoirs, irrigation ditches, marshes, and ponds. The colonization is necessary for protecting their populations. For tadpoles, permanent water is ideal for growth as they last between 12 months to 48 months before reaching adult stage[27]. As for the adult American bullfrogs, the habitat ideal for reproduction is in warmer temperatures.

7. Behaviors
   • Mate finding and mating

Mate finding in American bullfrog is done through competition. The male is also described to continue with its mating ritual throughout the mating season. The idea is to improve the chance of multiple mating with multiple females. The competition for the females creates a male-to-male competition, which is often high in the bullfrog population. Additionally, sexual selection among females ends up being an intense process. During the process, the male bullfrogs aggregate into groups to form choruses[28]. The male chorus trait is common and is dynamic. The association in choruses often lasts for a few days before merging into new territories with new males. The choruses are considered as centers for attraction for the females. Choruses, in addition, are regarded as defense mechanisms where individual choruses are defenseless. Studies show that the choruses are determined to be a good choice by the females[29]. For instance, a good chorus can range from having a low male population and maintains clearer territories that are deemed suitable for female choice. Social dominance within the choruses is also a form of mating. Within each chorus, there are behavioral issues of challenges, threats, and physical displays of dominance[30]. Older males may acquire more central roles compared to the younger males who are restricted to the periphery.

• Feeding

The American bullfrog is known to be an opportunistic, voracious, and ambush predator. It can prey on small animals that easily overpower and through their sticky tongue, swallow them. Bullfrogs during mating consume larger prey, including rodents, small lizards, and snakes, as well as other frogs[31]. It can also consume amphibians, crayfish, toads, tarantulas, and bats, including other invertebrates. The uniqueness of the mating and feeding defense is based on the geographical region.

• Defense

Mature male American bullfrogs are highly territorial anurans. They protect their space from other American bullfrogs as well as other types of frogs by either attack through lots of leaping and running pursuits or grappling[32].  They will kick or smack their adversaries. As for vocalization, the American bullfrogs frequently employ defensive vocalizations as a means to protect themselves. Vocalization is an attempt to call out with the goal of danger, whether with fellow American bullfrogs or other types of predators. The vocalization is quick and loud with a piercing and unpleasant sound to hear, according to scientists[33]. The sound is very different from the inviting and soothing sound during mating. Another tactic is through biting the opponent[34]. American bullfrogs are known to have teeth and a substantial wide mouth, which is capable of inflicting some intense painful bites on adversaries.

• Offense

The American bullfrogs are known to attack any prey that is within their reach. They are normal dormant throughout the day, and prey motion elicits feeding behavior. The frog will perform a single oriented body rotation ending with the frog facing the prey[35]. The following st is to take an approaching leap when necessary. If the frog is within striking distance, the American bullfrog will emit its feeding process[36]. It includes eyes are closed during the capture, the sticky tongue lunges in the mouth opening, the extension of the fleshy mucous-coated tongue which engulfs the prey and jaw continues to open if retracted back.

• Vocalizations

Vocalizations are differentiated into three aspects: mate callings, advertisement call, and encounter calls. Advertisement callings are common among the anuran category. The males make this call during the breeding season to establish territory and repel rival males in order to attract potential mates. The call is made in or near water bodies, which is an ideal place for the females to lay the eggs[37]. The advertisement calls are heard either in evenings or nights. For the American bullfrog, the call is very loud, low-pitched bellow. In some cases, it is reported that the older female American bullfrogs will vocalize at the same time with males to increase competition among the male’s[38]. The second type of vocalization is alarm calls. The alarm call is a fast squeak made before a jump to escape from the water. The last one is the encounter call. It is made by the male bullfrog through a sharp short call whenever another male bullfrog comes too close to its territory[39].  Another type of vocalization is the distress call, which is made when the frog is under stress, and it may emit a loud open-mouthed screaming sound, which is described as very disturbing to hear.

Discussion

I have learned a lot about the American bullfrog. The interesting aspect is that it is an invasive species which entails the occupation in other non-native territories. In addition to this, it can consume the native species within the new territory.  Another interesting fact about the American bullfrog is that it has teeth. The teeth presence and its large mouth are ideal for the consumption of unfathomable prey such as bats, fish, other amphibians and even, birds. The American bullfrog as an invasive species is facilitated by growing human interference. It entails human consumption whereby humans are placing them in large ponds and man-made reservoirs for harvest. These activities are not only conducted in America but the rest of the world, primarily in Asia. Throughout the research, American bullfrogs are known to be more aggressive and voracious compared to other types of frogs in America. Their mating rituals are even more aggressive, given the increased competition for female mating. Their mating season lasts for two to three months. During this period, the males are consistent in lasting longer in the mating grounds than the females. The idea is to increase the chances of mating with multiple females. To improve on the possibility of mating with multiple females, American bullfrogs arrange themselves in choruses. Choruses are the arrangement of frogs to increase the chances of mating with females, but it has conditions. The older bullfrogs gain dominant roles compared to the younger ones. They get the center position, whereas; the younger males get the periphery positions. The better equipped the choruses are, the better the chances. During the breeding period, the male bullfrogs have a distinct vocal call for the females as well as vocal calls for adversaries.

Bibliography

CABI. Invasive Species Compendium. [Internet]; 2020. Available from https://www.cabi.org/isc/datasheet/66618

Louette G, Devisscher S, Adriaens T. Control of invasive American bullfrog Lithobates catesbeianus in small shallow water bodies. European Journal of Wildlife Research;  2013 Feb 1;59(1):105-14.

Roach, John. Invading Bullfrogs Appear Nearly Unstoppable. [Internet}. National Geographic; 2004. Available from https://www.nationalgeographic.com/animals/2004/09/news-bullfrogs-invading-nearly-unstoppable/

USGS. Nonindigenous Aquatic Species. [Internet]. 2020. Available from https://nas.er.usgs.gov/queries/FactSheet.aspx?SpeciesID=71

[1] CABI. Invasive Species Compendium. [Internet]; 2020. Available from https://www.cabi.org/isc/datasheet/66618

[2] Roach, John. Invading Bullfrogs Appear Nearly Unstoppable. [Internet}. National Geographic; 2004. Available from https://www.nationalgeographic.com/animals/2004/09/news-bullfrogs-invading-nearly-unstoppable/

[3] CABI. Invasive Species Compendium. [Internet]; 2020. Available from https://www.cabi.org/isc/datasheet/66618

[4] Roach, John. Invading Bullfrogs Appear Nearly Unstoppable. [Internet}. National Geographic; 2004. Available from https://www.nationalgeographic.com/animals/2004/09/news-bullfrogs-invading-nearly-unstoppable/

[5] CABI. Invasive Species Compendium. [Internet]; 2020. Available from https://www.cabi.org/isc/datasheet/66618

[7] CABI. Invasive Species Compendium. [Internet]; 2020. Available from https://www.cabi.org/isc/datasheet/66618

[8] CABI. Invasive Species Compendium. [Internet]; 2020. Available from https://www.cabi.org/isc/datasheet/66618

[9] Roach, John. Invading Bullfrogs Appear Nearly Unstoppable. [Internet}. National Geographic; 2004. Available from https://www.nationalgeographic.com/animals/2004/09/news-bullfrogs-invading-nearly-unstoppable/

[10] Roach, John. Invading Bullfrogs Appear Nearly Unstoppable. [Internet}. National Geographic; 2004. Available from https://www.nationalgeographic.com/animals/2004/09/news-bullfrogs-invading-nearly-unstoppable/

[11] Roach, John. Invading Bullfrogs Appear Nearly Unstoppable. [Internet}. National Geographic; 2004. Available from https://www.nationalgeographic.com/animals/2004/09/news-bullfrogs-invading-nearly-unstoppable/

[12] CABI. Invasive Species Compendium. [Internet]; 2020. Available from https://www.cabi.org/isc/datasheet/66618

[13] Roach, John. Invading Bullfrogs Appear Nearly Unstoppable. [Internet}. National Geographic; 2004. Available from https://www.nationalgeographic.com/animals/2004/09/news-bullfrogs-invading-nearly-unstoppable/

[14] USGS. Nonindigenous Aquatic Species. [Internet]. 2020. Available from https://nas.er.usgs.gov/queries/FactSheet.aspx?SpeciesID=71

[15] CABI. Invasive Species Compendium. [Internet]; 2020. Available from https://www.cabi.org/isc/datasheet/66618

[16] CABI. Invasive Species Compendium. [Internet]; 2020. Available from https://www.cabi.org/isc/datasheet/66618

[17] CABI. Invasive Species Compendium. [Internet]; 2020. Available from https://www.cabi.org/isc/datasheet/66618

[18] Roach, John. Invading Bullfrogs Appear Nearly Unstoppable. [Internet}. National Geographic; 2004. Available from https://www.nationalgeographic.com/animals/2004/09/news-bullfrogs-invading-nearly-unstoppable/

[19] Roach, John. Invading Bullfrogs Appear Nearly Unstoppable. [Internet}. National Geographic; 2004. Available from https://www.nationalgeographic.com/animals/2004/09/news-bullfrogs-invading-nearly-unstoppable/

[20] CABI. Invasive Species Compendium. [Internet]; 2020. Available from https://www.cabi.org/isc/datasheet/66618

[21], Roach, John. Invading Bullfrogs Appear Nearly Unstoppable. [Internet}. National Geographic; 2004. Available from https://www.nationalgeographic.com/animals/2004/09/news-bullfrogs-invading-nearly-unstoppable/

[22]s CABI. Invasive Species Compendium. [Internet]; 2020. Available from https://www.cabi.org/isc/datasheet/66618

[23] Roach, John. Invading Bullfrogs Appear Nearly Unstoppable. [Internet}. National Geographic; 2004. Available from https://www.nationalgeographic.com/animals/2004/09/news-bullfrogs-invading-nearly-unstoppable/

[24] CABI. Invasive Species Compendium. [Internet]; 2020. Available from https://www.cabi.org/isc/datasheet/66618

[25] Roach, John. Invading Bullfrogs Appear Nearly Unstoppable. [Internet}. National Geographic; 2004. Available from https://www.nationalgeographic.com/animals/2004/09/news-bullfrogs-invading-nearly-unstoppable/

[26] CABI. Invasive Species Compendium. [Internet]; 2020. Available from https://www.cabi.org/isc/datasheet/66618

[27] CABI. Invasive Species Compendium. [Internet]; 2020. Available from https://www.cabi.org/isc/datasheet/66618

[28] Roach, John. Invading Bullfrogs Appear Nearly Unstoppable. [Internet}. National Geographic; 2004. Available from https://www.nationalgeographic.com/animals/2004/09/news-bullfrogs-invading-nearly-unstoppable/

[29] Louette G, Devisscher S, Adriaens T. Control of invasive American bullfrog Lithobates catesbeianus in small shallow water bodies. European Journal of Wildlife Research;  2013 Feb 1;59(1):105-14.

[30] CABI. Invasive Species Compendium. [Internet]; 2020. Available from https://www.cabi.org/isc/datasheet/66618

[31] Louette G, Devisscher S, Adriaens T. Control of invasive American bullfrog Lithobates catesbeianus in small shallow water bodies. European Journal of Wildlife Research;  2013 Feb 1;59(1):105-14.

[32] Louette G, Devisscher S, Adriaens T. Control of invasive American bullfrog Lithobates catesbeianus in small shallow water bodies. European Journal of Wildlife Research;  2013 Feb 1;59(1):105-14.

[33] Roach, John. Invading Bullfrogs Appear Nearly Unstoppable. [Internet}. National Geographic; 2004. Available from https://www.nationalgeographic.com/animals/2004/09/news-bullfrogs-invading-nearly-unstoppable/

[34]‘s CABI. Invasive Species Compendium. [Internet]; 2020. Available from https://www.cabi.org/isc/datasheet/66618

[35] Louette G, Devisscher S, Adriaens T. Control of invasive American bullfrog Lithobates catesbeianus in small shallow water bodies. European Journal of Wildlife Research;  2013 Feb 1;59(1):105-14.

[36] Roach, John. Invading Bullfrogs Appear Nearly Unstoppable. [Internet}. National Geographic; 2004. Available from https://www.nationalgeographic.com/animals/2004/09/news-bullfrogs-invading-nearly-unstoppable/

[37] Louette G, Devisscher S, Adriaens T. Control of invasive American bullfrog Lithobates catesbeianus in small shallow water bodies. European Journal of Wildlife Research;  2013 Feb 1;59(1):105-14.

[38] Roach, John. Invading Bullfrogs Appear Nearly Unstoppable. [Internet}. National Geographic; 2004. Available from https://www.nationalgeographic.com/animals/2004/09/news-bullfrogs-invading-nearly-unstoppable/

[39] CABI. Invasive Species Compendium. [Internet]; 2020. Available from https://www.cabi.org/isc/datasheet/66618