Gastrophryne carolinensis, the eastern narrow-mouthed toad, is a species of microhylid frog. It is a relatively small, toad-like amphibian found in damp, shady habitats. The species is highly fossorial, and feeds primarily on ants. These North American microhylids (Family: Microhylidae) are distinguished from true toads (genus Bufo), and other anurans by their moist, smooth skin, their lack of eardrums or tympana, their distinguishable squat body shape, and the unique fold of skin superior to their eyes. It is found in the United States, from southern Maryland to the Florida Keys, west to Missouri and Texas. While not a true toad, it is so called because it is terrestrial.
Taxonomy
Gastrophryne carolinensis belongs to one of the largest anuran families, the microhylids. No subspecies are currently recognized. The Eastern narrowmouth toad is one of only 3 microhylids that currently live in the United States.
Description
The eastern narrow-mouthed toad is relatively small, growing to a maximum length of . It has an oval-shaped body and a narrow head with a pointed snout. On the back of their head, they have a fold of skin that is capable of covering their eyes. They vary in color from brown and grey to green, often with black and white spotting. Usually there will be a dark brown stripe seen on both sides of the body. Gastrophryne carolinensis toads have a typical teardrop-shaped body that is characteristic of members of the family Microhylidae. Though its morphology lacks a tympanum (eardrum), the subgular vocal sac is clearly visible. The toes are long and unwebbed.
The skin of G. carolinensis is smooth and without ridges or warts. Yet, the skin is extremely tough, which most likely protects them from the ants upon which they feed. Directly behind the eyes, resting on the toads neck, is a distinctive skin fold evolved for protection from ant bites while feeding.
The color of the toad can change depending on its activities and environment. The colors on its sides are generally faded, but its dorsum is dark and broad with various light or dark spots, mottling, or patches that cover the light strip along its middorsal area. Its abdomen is generally highly mottled, but its ventral surface is nearly light or unmarked. The venters of certain narrow-mouthed toads in the Great Plains are generally unmarked, or virtually so, while those of eastern toads are strongly pigmented.
Its legs are generally stubby, short, and heavy, and the tips of the toes are round and tapered. As with the Leptodactylidae, the toes are absent of webbing or toe pads. However, the heels on the back feet have one "spade" or tubercle for digging.
The sex of the eastern narrow-mouthed toad can easily be determined by the characteristic sexual dimorphism. The color of the throat region for males is dark and highly pigmented, while the female throat is absent of this discriminate coloring.
G. carolinensis has a call that is said to sound like a bleating sheep or an electric buzzer; it is somewhat similar to the call of Anaxyrus fowleri.
Range
The narrow-mouthed toad can reach elevations up to 550 m (1,800 ft). They are generally absent from most Blue Ridge Mountains and the Appalachian Mountains.
Gastrophyryne carolinensis is only one of three species belonging to the family Microhylidae native to the United States. The species resides in the southeastern quarter of the US, extending from Missouri and eastern Texas and from southern Maryland to the Florida Keys, as well as in an isolated colony in Iowa. Many have also been introduced to the little and great Bahamas, as well as the Cayman Islands.
Although they live in a broad range of habitats and are rather ubiquitous, their most important environmental variables must include moisture and shelter. They reside in either freshwater or terrestrial systems, and are able to use both temporary and permanent waters, as well as man-modified habitats. The members of this species tend to discount dry areas and mountains, though some may live in near desert-like conditions. Adults of this species are tolerant of brackish water so they have been able to inhabit barrier islands and coastal marshes.
General habitat types include: Borders of swamps Cypress-gum swamps Bottomland hardwoods Live-oak ridges Pine-oak uplands Sandy woodlands and hillsides Open woods Pine forests Coastal secondary dune scrub forest Maritime forests Small streams Beneath logs Near ponds with fallen logs and other debris Urban habitats such as: Woodland lots Sandy pinelands Suburban habitats such as: Sandy soils around the lawn