Anaxyrus: Spotlight on North American True Toads

The genus Anaxyrus comprises true toads classified under the family Bufonidae. Most of the species under this genus were formerly classified under the genus Bufo. It encompasses a wide range of spices, each bearing unique characteristics, with one of the most well-known members of this genus being the American toad (Anaxyrus americanus). These toads inhabit various regions across North America.

In this article, we will explore more about the true toads under the genus Anaxyrus. We’ll provide you with an overview of the genus Anaxyrus and discuss the main iconic species, the American toad, including its unique characteristics, distribution, and ecological significance of these remarkable amphibians. We will also shed light on the taxonomic reclassification of species from genus Bufo to Anaxyrus.

Overview of Anaxyrus species

The Anaxyrus is a Greek word meaning a king or chief. In this context, it serves as the genus of true toads in the Bufonidae family. This genus is endemic to North and Central America.

As we have just said in the intro above, the genus Anaxyrus boasts a wide array of true toads, each of which contributes to North America’s diversity.

Some of these species under the genus Anxyrus include:

• American toad (Anaxyrus americanus)
• Western toad (Anaxyrus boreas)
• Wyoming toad (Anaxyrus baxteri)
• Yosemite toad (Anaxyrus canorus)
• Great Plains toad (Anaxyrus cognatus)
• Fowler’s toad (Anaxyrus fowleri)
• Southwestern toad (Anaxyrus mexicanus)
• Little Mexican toad (Anaxyrus kelloggi)
• Red-spotted toad (Anaxyrus punctatus)
• Sonoran green toad (Anaxyrus retiformis)
• Woodhouse’s toad (Anaxyrus woodhousii)

Among these, the American toad (Anaxyrus americanus) emerges as the iconic representative that captures the genus diversity

The American toad is quite widespread throughout large parts of North America and native to the Nearctic region.

This toad has a great ability to adapt to their surroundings provided there’s a semi-permanent water source for them to use during the breeding season. This has enabled it to successfully colonize the agricultural and suburban areas.

In terms of appearance, this toad is usually 2 to 3.5 inches long and features a stout body, short legs, and thick skin with noticeable warts that can be yellow or red.

Its warty skin features prominent parotid glands that secrete a poisonous milky white substance, Bufotoxin, which provides the toad with excellent protection against predators.

Its skin coloration is usually brown, but it can vary to red with some light patches, gray, or olive. Its belly is white or yellow.

Note that the toad’s skin color can transform between yellow, brown, and black depending on stress, temperature, or humidity.

Males can be easily distinguished from females by their dark throats of brown or black color while females’ throats are white or overall lighter. The females are also larger than males.

The American toad can be distinguished from other toad species by the dark spots on its back, each containing 1-2 warts. These sports are sometimes circled with yellow or white.

Since the adult toads are cryptic colored which enables them to blend in with their surroundings and are only active at night, they can survive in the wild as predators have a hard time finding them.

Transition from genus Bufo to Anaxyrus

The genus name for some true toads was changed from Bufo to Anaxyrus in 2006.

This was after the scientists were able to prove that some of the species earlier classified under genus Bufo were sufficiently different and should be placed in separate genera.

In other words, this transition aimed to better align the toad species taxonomy with the evolutionary relationships.

In the scientific world, this change reflects advancements in genetic analysis and a better understanding of diversity and distinctiveness within the true toad family Bufonidae.

Note that not all the toads under the genus Bufo were transferred to Anaxyrus.

Distribution across North America

The Anaxyrus toads are geographically distributed across North America. This shows their remarkable ability to adapt to diverse landscapes in this region.

One of the distinct areas where these true toads are found in North America is in the eastern woodlands.

Toads in this region inhabit the moist environments of the coniferous and deciduous forests, where they navigate through the vegetation and leaf litter in search of prey.

Some Anaxyrus toad species also inhabit the southwestern arid regions, where they are found in regions experiencing lower precipitation, e.g. semi-arid landscapes and deserts.

Throughout their native range, these toads inhabit a wide range of habitats, including grasslands, meadows, and even urban environments.

Note that the Anaxyrus true toads coexist with other species in their range.

Their ecological interaction with these species, whether in terms of competition for resources or as contributors to the food webs of their ecosystems paints a clear picture of the interconnectedness of the northern American ecosystems.

Anaxyrus life cycle and reproduction

Anaxyrus toads undergo several distinct stages in their life cycles as with most other toad species.

Their lifecycle starts with egg laying in aquatic environments, e.g. slow-moving streams and ponds. Females lay gelatinous egg masses that are often attached to the submerged vegetation.

The eggs undergo development in aquatic environments, where the environmental conditions play a crucial role in their hatching success. The eggs eventually mature and develop into aquatic larvae known as tadpoles.

Tadpoles then continue developing in the aquatic environment. They undergo a series of developmental stages including absorption of their tail and development of limbs. This development is usually facilitated by the availability of food sources in the aquatic environment.

Once they become fully developed, toadlets leave the waters and join their adult counterparts on the land. Here, they continue with their development into sexual maturity.

Breeding behavior for these toads starts with males gathering near breeding sites and making mating calls to attract females. These calls are species-specific and range from distinct vocalizations to melodious trills.

Once the females show up at breeding grounds, they engage in mating rituals and they lay eggs as the males eternally fertilize them.

Ecological significance

The Anaxyrus toads play a crucial role in maintaining the ecological balance in their native habitats, especially through their contributions to pest control.

Their food habits and position in the food web make them effective insect population controllers.

Toads under the genus Anaxyrus such as American toads, generally exhibit opportunistic feeding behavior. They consume a wide variety of insects. They also consume other small invertebrates such as beetles, mosquitoes, ants, etc.

This ability to consume and thus control insect populations helps mitigate the impact these insects can have on the vegetation and other fauna. As such, the toads help maintain the health of their ecosystems.

Not to forget, these toads also act as prey for other animals in their ecosystem. This further contributes to a healthy and balanced ecosystem.

Like most other toads, Anaxyrus toads are also sensitive to their environment. Therefore, they serve as excellent indicators of the health of their ecosystems.

They are highly sensitive to changes in water quality, temperature, habitat alterations, etc. Their absence or presence in a given environment is a solid signal of the environmental changes.

Anaxyrus conservation status

Like most other toad species, the Anaxyrus toads face several threats in the wild that pose challenges to their populations as well as the ecosystems they inhabit.

Understanding and addressing these threats will help conserve these iconic amphibians of North America.

Let’s take a closer look at some of these threats:

• Habitat loss: One of the key threats to the population of these toads is habitat loss. Agriculture, infrastructure development, and urbanization interfere with the natural habitats these toads depend on for foraging, breeding, and shelter. As the vital habitats continue to diminish, the toads face fragmentation and isolation, affecting their thrivability and even diminishing the ecosystems’ overall biodiversity.
• Pollution: The toads also face the detrimental effects of pollution. Specifically, they’re affected by water pollution caused by industrial discharges, agricultural runoff, and various other contaminants. These tend to compromise the quality of their breeding sites, thus affecting the health of tadpoles as well as adult toads.
• Infectious diseases: Diseases such as the deadly chytridiomycosis are also known to affect the amphibian populations all over the world and the Anaxyrus species aren’t an exception.

Because these species play a crucial role in the ecological balance of North American habitats, putting in place conservation measures is necessary to help safeguard their populations.

Some of these efforts include raising public awareness and educating the communities on the importance of these amphibians, the threats they face, and the need for collective responsibility to protect their habitats.

Responsible land management and practices are another helpful conservation measure. This will help mitigate the habitat loss impact.

Conservationists, landowners, and policymakers can work together to come up with strategies that balance human activities with critical habitat preservation. This will help ensure the long-term viability of the Anaxyrus toads.

Conclusion

The genus Anaxyrus constitutes a true toad species native to North America. Many species fall under this genus, with the American toad (Anxyrus amerixanus) being the most iconic member. These true toads are found in various types of habits throughout the northern American region and play crucial roles in maintaining the health and balance of their ecosystems.

Similar to other toad species, the Anaxyrus toads also produce toxins as a defense mechanism against predators. Though most of the Anaxyrus toads are plentiful in the wild, they still face various threats including habitat loss, pollution, and infectious diseases. These may cause a decline in their populations in the future, hence the need to put in place various conservation measures to preserve their populations.