Taken from: National Audubon Society Field Guide
to North American Reptiles and Amphibians
Copyright: Chanticleer Press, Inc., 1979

AMPHIBIANS
(class Amphibia)

Living amphibians comprise three major groups, 2 of which occur in our range: The salamanders (order Caudata) and the frogs and toads (order Salientia). While the oldest fossil salamanders and frogs can only be traced back about 150 million years, their ancestors evolved from the fishes of the early Devonian Period, appearing about 350 million years ago. The amphibians were the first vertebrates to face the rigors of life on land. They solved locomotion and air breathing problems but remained terrestrial existence and were never able to divorce themselves completely from the aquatic environment. However, skin and shelled eggs offered protection against excessive water loss, thus enabling them to advance into an unoccupied arid habitat.

FROGS AND TOADS
(Order Salientia)

There are nearly 2,700 species of frogs and toads known. They are divided into 16 families, with 9 occurring in North America. The remainder are found in South America, Europe, Africa, Asia, Australia, and the South Pacific islands. A total of 81 species occur north of Mexico.

Adult frogs and toads lack tails. They have well-developed forelimbs and even larger hind legs. They lack a clear neck, the head seeming to be attached directly to the body. Most have a well-developed ear, as evidenced externally by a conspicuous tympanum, and a voice used to attract mates, drive off intruders, and to signal distress and presence. All are carnivorous as adults. With their moist skin, most frogs and toads are prone to desiccation, and therefore are confined to wet or moist habitats. However, some species have adapted to more arid habitats by burrowing into the soil or hiding beneath rocks or logs to avoid the heat of the day.

Most species return to water to breed. Eggs laid in the water are fertilized by the male while clasping the female. The eggs hatch into tadpoles which later transform into young frogs. A number of frogs and toads lay their eggs in shaded moist sites on land, or in nests constructed over water. The eggs may hatch into tadpoles that either drop into the water, are swept into the water by rains, or are carried to water by the parent. Other species bypass the tadpole stage, their eggs hatching directly into miniature frogs. Finally, the African live-bearing toad, Nectophrynoides, and the North American tailed frog, Ascaphus, are unique among frogs and toads in fertilizing the eggs within the cloaca of the female.

TAILED FROG FAMILY
(Ascaphidae)

Two genera: Leiopelma with 3 species in New Zealand, and Ascaphus with 1 species in the northwestern United States and southwestern Canada.

These are primitive frogs with 2 pairs of unattached ribs and 9 presacral vertebrae. The pupil is vertical. None of the species has a true tail, but all possess tail-wagging muscles. Male Ascaphus have a unique tail-like extension of the vent that serves as a copulatory organ for passing sperm directly into the body of the female, while clasping her around the waist.

All tailed frogs live in cool mountain habitats, but reproduction varies: Leiopelma lays its eggs on damp earth where they hatch 6 weeks later as miniature frogs; Ascaphus lays its eggs in cold mountain streams where they hatch into tadpoles, transforming into frogs more than 6 months later.

Tailed Frog (Ascaphus truei)

BURROWING TOAD FAMILY
(Rhinophrynidae)

Only 1 species, Rhinophrynus dorsalis, found from Costa Rica to Texas.

This frog lacks a breastbone. The pupil is vertical. In addition, its tongue is attached in the back and free in the front, unlike the typical toad or frog, so that it protrudes like the tongue of most vertebraes. Rhinophrynus is adept at burrowing, making use of the spade on each hindfoot to shuffle backward into the soil. Breeding males clasp the female around the waist. Eggs are laid in water.

Mexican Burrowing Toad (Rhinophrynus dorsalis)

SPADEFOOT TOAD FAMILY
(Pelobatidae)

Ten genera with 69 species known; 1 genus in North America: Scaphiopus, with 5 species.

Spadefoots derive their names from the "spade," a horny, dar, sharp-edged tubercle on the inner surface of the hind foot, used to dig their daytime burrow. Scaphiopus differs from other North American coccyx, the bony end of the vertebral column, fused to the sacral vertebra.


The teeth on their upper jaw, the vertical pupils, relatively smooth skin, and absence of parotoid glands easily separate them from true toads (Family Bufonidae).

Breeding males clasp the female around the waist. Scaphiopus breeds in temporary rainpools which may dry up soon after the rains end. As an adaptation to this, spadefoots have an accelerated development. The total period of time from egg to tadpole to metamorphosed toad can be as little as 2 weeks.

Plains Spadefoot (Scaphiopus bombifrons)
Couch's Spadefoot (Scaphiopus couchi)
Western Spadefoot (Scaphiopus hammondi)
Eastern Spadefoot (Scaphiopus holbrooki)
Great Basin Spadefoot (Scaphiopus intermontanus)

TRUE FROG FAMILY
(Ranidae)

Forty-six genera with approximately 560 species worldwide. Only 1 genus in North America: Rana, with 21 species.

True frogs have a bony breastbone and horizontal pupils. North American species are large frogs with slim waists, long legs, pointed toes, and extensive webbing on the hind feet. They are excellent jumpers. The adults are truly amphibious, typically living along the edge of water and entering it daily to catch prey, flee danger, or to mate.


They are all voracious carnivores, feeding primarily on insects, spiders, and crustaceans, but readily accepting anything else that can be caught and swallowed.

Mating usually is initiated in the spring with aggregations of males calling in chorus to attract females to the breeding site. The breeding male has swollen forearms and thumbs for clasping the female behind her forelegs. In the water, female Rana may lay strings or rafts containing up to 20,000 eggs. Eggs hatch within a month, with tadpoles metamorphosing into frogs 6 to 24 months later.

Crawfish Frog (Rana areolata)
Red-legged Frog (Rana aurora)
Rio Grande Leopard Frog (Rana berlandieri)
Plains Leopard Frog (Rana blairi)
Foothill Yellow-legged Frog (Rana boylei)
Cascades Frog (Rana cascadae)
Bullfrog (Rana catesbeiana)
Green Frog (Rana clamitans)
Las Vegas Leopard Frog (Rana fisheri)
Pig Frog (Rana grylio)
River Frog (Rana heckscheri)
Mountain Yellow-legged Frog (Rana muscosa)
Relict Leopard Frog (Rana onca)
Pickeral Frog (Rana palustris)
Northern Leopard Frog (Rana Pipiens)
Spotted Frog (Rana Pretiosa)
Mink Frog (Rana septentrionalis)
Southern Leopard Frog (Rana sphenocephala)
Wood Frog (Rana sylvatica)
Tarahumara Frog (Rana tarachumarae)
Carpenter Frog (Rana virgatipes)

NARROW-MOUTHED FROG FAMILY
(Microhylidae)

Sixty-one genera with approximately 270 species known. Only 2 genera occur in our range: Gastrophryne with 2 species, and Hypopachus with 1 species.

Narrow-mouthed frogs have a reduced shoulder girdle. The North American species lack teeth, and have a fold of skin across the back of the narrow, pointed head. The body is plump and the skin smooth and moist. The legs are short and the hind feet have enlarged tubercles used in digging. They are secretive creatures active only at night; they feed almost exclusively on ants.


Males give a bleating call to attract females to the breeding ponds. In addition to being clasped firmly behind the forlimbs by the male, the female narrow-mouthed's sticky skin secretion also holds the breeding pair together. Eggs are laid in a thin floating film and hatch in a few days. Tadpoles metamorphose in about 30 days.

Eastern Narrow-mouthed Frog (Gastrophryne carolinensis)
Great Plains Narrow-mouthed Frog (Gastrophryne olivacea)
Sheep Frog (Hypopachus variolosus)

TOAD FAMILY
(Bufonidae)

Nineteen genera with approximately 300 species known. Only 1 genus occurs in our range: Bufo, with 18 species.

Toads are squat and plump with rough warty skin. They have horizontal pupils, no teeth on the upper jaw, and lack an anterior breastbone. Enlarged parotoid glands are located on each side of the neck over or behind the tympanum. These glands secrete a viscous white poison, which gets smeared in the mouth of any would-be predator. The poison inflames the mouth and throat, causes nausea, irregular heart beat, and, in extreme cases, death. Survivors of such a poisoning seldom ever again attack toads.


Bufo breeds in spring and summer. Males congregate at the breeding ponds and sing in order to attract females. Males clasp the willing females around the body behind the forelimbs. Males also have a rudimentary ovary, which can become functional if the testes are damaged or removed. Eggs are usually laid in strings attached to vegetation; they hatch into timy black tadpoles, which weeks later metamorphose.

Colorado River Toad (Bufo alvarius)
American Toad (Bufo americanus)
Western Toad (Bufo boreas)
Yosemite toad (Bufo Canorus)
Great Plains Toad (Bufo cognatus)
Green Toad (Bufo debilis)
Black Toad (Bufo exsul)
Canadian Toad (Bufo hemiophrys)
Houston Toad (Bufo houstonensis)
Giant Toad (Bufo marinus)
Southwestern Toad (Bufo microscaphus)
Red-spotted Toad (Bufo punctatus)
Oak Toad (Bufo quercicus)
Sonoran Green Toad (Bufo retiformis)
Texas Toad (Bufo Speciosus)
Southern Toad (Bufo terrestris)
Gulf Coast Toad (Bufo valliceps)
Woodhouse's Toad (Bufo woodhousei)

TREE FROG FAMILY
(Hylidae)

Thirty-four genera with approximately 600 species known. Seven genera with 26 species occur in our range. Tree frogs are small and have slender legs; their pupils are horizontal.

Arboreal tree frogs are typically walkers and climbers-----they are reluctant jumpers. Their toe tips are expanded into sticky adhesive pads used in climbing. Climbing is further aided by the presence of a cartilage between the last 2 bones of each toe. The cartilage allows the tip of the toe to swivel backward and sideways while keeping the sticky toe pad flat against the climbing surface. A few tree frogs, such as the North American Acris, have returned to a terrestrial existence, lack large toe pads, and are active leapers.

Male tree frogs in our range typically call while perched on vegetation in, over, or near water. Males clasp females just behind the forelimbs; masses of eggs are laid in the water.

Northern Circket Frog (Acris crepitans)
Southern Cricket Frog (Acris gryllus)
Pine Barrens Tree frog (Hyla andersoni)
Canyon Tree frog (Hyla arenicolor)
Bird-voiced Tree frog (Hyla avivoca)
California Tree frog (Hyla cadaverina)
Cope's Gray Tree frog (Hyla chrysoscelis)
Common Gray Tree frog (Hyla versicolor)
Green Tree frog (Hyla cinerea)
Spring Peeper (Hyla crucifer)
Mountain Tree frog (Hyla eximia)
Pine Woods Tree frog (Hyla femoralis)
Barking Tree frog (Hyla gratiosa)
Pacific Tree frog (Hyla regilla)
Squirrel Tree frog (Hyla squirella)
Little Grass Frog (Limnaoedus ocularis)
Cuban Tree frog (Osteopilus septentrionalis)
Mountain Chorus Frog (Pseudacris brachyphona)
Brimley's Chorus Frog (Pseudacris brimleyi)
Spotted Chorus Frog (Pseudacris clarki)
Southern Chorus Frog (Pseudacris nigrita)
Ornate Chorus Frog (Pseudacris ornata)
Strecker's Chorus Frog (Pseudacris streckeri)
Chorus Frog (Pseudacris triseriata)
Burrowing Tree frog (Pternohyla fodiens)
Mexican Tree frog (Smilisca baudini)

LEPTODACTYLID FROG FAMILY
(Leptodactylidae)

Fifty genera of about 650 species occur in Australia, southern Africa, and the tropical Americas; 4 genera with 7 species occur in our range.

Leptodactylids are an extremely diverse group adapted to a variety of habitats and reproductive strategies. The 7 species that occur in our section of North America have horizontal pupils and a T-shaped bone in the tip of each toe.


Males of some species congregate together to call in loud choruses to attract females to the breeding ponds, but males of most species call singly, often while hidden in vegetation or burrows. Breeding males clasp the females behind the forelimbs. Some species, like Leptodactylus, lay numerous eggs in foam nests in the water. On hatching, the tadpoles escape inot the water where they live until metamorphosing into frogs. Other species, like Eleutherodactylus, lay fewer than two dozen eggs in moist leaf litter or damp earth. They hatch 2 to 3 weeks later, releasing fully developed miniature frogs.

Puerto Rican Coqui (Eleutherodactylus coqui)
Greenhouse Frog (Eleutherodactylus planirostris)
Barking Frog (Hylactophryne augusti)
White-lipped Frog (Leptodactylus labialis)
Rio Grand Chirping Frog (Syrrhophus cystignathoides)
Spotted Chirping Frog (Syrrhophus guttilatus)
Cliff Chirping Frog (Syrrhophus marnocki)

TONGUELESS FROG FAMILY
(Pipidae)

Four genera: Pipa with 6 species in South America, and Xenopus, Hymenochirus, and Pseudhymenochirus with 14 species in Africa. One species Xenopus laevis, has been introduced to North America.

Tongueless frogs have attached ribs and eight presacral vertebrae. Their pupils are round. The South American species have starlike projections on the tips of the toes of the front feet; the African species have simple pointed toes on the front feet. The latter attach their eggs singly to submerged vegetation, logs, or stones; thousands of eggs are laid. During breeding, males clasp the female around the waist.

African Clawed Frog (Xenopus laevis)

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