Eastern Narrow-Mouthed Toad

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Image of an eastern narrow-mouthed toad
Scientific Name
Gastrophryne carolinensis
Family
Microhylidae (narrow-mouthed toads) in the order Anura (frogs)
Description

The eastern narrow-mouthed toad is a small, plump, burrowing amphibian with a distinct fold of skin behind a small, narrow, pointed head. This animal has short legs, there is no external eardrum (tympanum), and no webbing between the toes.

The general color is tan, brown, or reddish brown. The back has a pattern that looks like a long, dark wedge pointing toward the head. This dark wedge is bordered by a wide lateral stripe of lighter color. Below that is a dark stripe running from the snout to the side of the hind legs. These patterns are often obscured by the presence of numerous small dark brown or black markings. The belly is mottled with dark gray. Characteristics of this burrowing species include a small, pointed head, a fold of skin across the back of the head, short legs, and the absence of both an external eardrum (tympanum) and webbing between the toes. Males can be distinguished from females by their deeply pigmented throat.

The call of a male eastern narrow-mouthed toad is a bleating, nasal “baaaaa”; it lasts 1–4 seconds, sounding like the call of a lamb. When one individual calls, it often causes other individuals to call simultaneously.

Similar species: The western narrow-mouthed toad, a close relative, has a lighter color and lacks prominent markings on the back. Also, its call is quite different, being a high-pitched, short “peep” followed by a nasal buzzy bleat. Missouri's two narrow-mouthed toads have different distributions in the state, but the ranges do overlap in several western counties. In these counties, populations may occur in the same area. However, the calls of both species are different enough to prevent them from hybridizing.

The narrow-mouthed toads (Microhylidae) are a large family of burrowing, secretive frogs. The family has representatives in Asia, Malaysia, northern Australia, New Guinea, southern Africa, Madagascar, and North and South America. The group probably originated in Asia. The family contains 63 genera with 557 species. In the United States, this group is represented by two genera and four species; of these, two species of one genus (Gastrophryne) live in Missouri. Most members of this group are fossorial (burrowing), spending most of their time in burrows or under rocks or logs. They tend to be small, plump, and squatty in appearance. All species in the United States have a characteristic fold of skin behind a small, narrow, pointed head. Although they may eat many types of small insects, these amphibians are mostly ant eaters.

Size

Adult length (snout to vent): 1 to 1¼ inches, occasionally to 1½ inches.

Where To Find
Eastern Narrow-Mouthed Toad

Throughout most of the southern half of the state. It has a large range to the east and south of our state.

In Missouri, the eastern narrow-mouthed toad lives in a variety of habitats, including flooded swamps, open grasslands, and upland and bottomland hardwood woodlands. This toad spends most of its time in loose, damp soil under rocks and logs. It prefers a habitat where shelter and moist soil are available, usually near ponds, swamps, and streams. In the Ozarks, however, individuals do occur under flat rocks on relatively dry glades.

Once an eastern narrow-mouthed toad is uncovered, it tries to escape with a series of quick, short hops and a scramble into leaf litter or another nearby hiding place.

Although they are mainly found on the ground beneath cover, an individual was found in a dead stump nearly 8 feet off the ground. They may create their own short burrow or use burrows created by other animals. An individual will often sit in a burrow with its head slightly visible at the surface awaiting prey.

Eastern narrow-mouthed toads primarily eat ants, although they also eat termites, small beetles, and spiders. Eastern narrow-mouthed toads have evolved a skin secretion that is noxious to many predators; the secretion also protects them from the defensive bites of ants. They typically sit on anthills while eating their preferred food.

Life Cycle

This species usually breeds in large puddles, temporary pools, fishless flooded ditches, and fields, including rice fields in southeastern Missouri. They will, however, occasionally use permanent bodies of water, especially sites with thick vegetation and shallow edges.

Males begin chorusing in late April, and chorusing can also take place during the summer months, especially in June or early July after heavy rains. Males usually hide under leaves or other debris at the water’s edge, or they may sit in thick vegetation within the water as they call. Special glands on the male’s belly secrete a gluey substance that sticks the mating pair together. Females can lay over 1,000 eggs in several films on the surface of the water. In Missouri, females lay an average of 510 eggs. The membrane envelope surrounding the egg is unique to this genus: it is circular, with one or more flat surfaces that might resemble a mosaic pattern. The eggs hatch in fewer than 3 days. The tadpoles develop rapidly, becoming toadlets in 30–60 days. They become sexually mature in 1–2 years.

As predators, these amphibians help control populations of many insects that are pests to humans. Additionally, their beautiful and strange singing adds to the magic of a Missouri evening.

The genus name, Gastrophryne, means "stomach-toad." It's a great name for these pudgy-looking animals.

Narrow-mouthed toads are predators that help keep populations of ants and other insects in balance. Due to their specialized diet of consuming many types of ants, including exotic and invasive species, narrow-mouthed toads might benefit from these new food sources. They might also be be helpful in controlling invasive ants.

These toads, and especially their eggs, tadpoles, and young toadlets, become food for both aquatic and terrestrial predators. Their noxious skin secretion apparently helps defend them from at least some predators.

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About Reptiles and Amphibians in Missouri
Missouri’s herptiles comprise 43 amphibians and 75 reptiles. Amphibians, including salamanders, toads, and frogs, are vertebrate animals that spend at least part of their life cycle in water. They usually have moist skin, lack scales or claws, and are ectothermal (cold-blooded), so they do not produce their own body heat the way birds and mammals do. Reptiles, including turtles, lizards, and snakes, are also vertebrates, and most are ectothermal, but unlike amphibians, reptiles have dry skin with scales, the ones with legs have claws, and they do not have to live part of their lives in water.