Types of Frogs

Frogs and toads, the tailless amphibians (order Anura) multiple habitat across North America.

Scientists organize the approximately 5,000 different frog and toad species into twenty-five families.

The ninety North American species span all nine families. Approximately eighty per cent of those species fit into one of three families: true frogs (Ranidae); tree frogs (Tree Frogs) and true toads (Bufonidae).

Ascaphidae: Tailed Frogs (1 species)
Bufonidae: True Toads (21 species)
Hylidae: Tree Frogs (25 species)
Leptodactylidae: Neotropical Frogs (6 species)
Microhylidae: Narrow-mouthed Frogs (2 species)
Pelobatidae: Spadefoots (7 species)
Pipidae: Tongueless Frogs (1 species)
Ranidae: True Frogs (26 species)
Rhinophrynidae: Burrowing Toads (1 species)

Most discussions of frog types include references to toad and frog differences.

Physically, moist smooth skin serves as the basic frog description, contrasted with the toad's dry, warty skin.

A quick look at the first video and picture, the Western Toad and the Bullfrog respectively, confirms those basic differences.

Physical characteristics and habitat also serve as the primary differences between frogs and tree frogs. The name tree frog suggests that family members live an arboreal lifestyle. They also tend to be smaller than true frogs.

The second video shows a Pacific Chorus Frog (Pseudacris regill) resting on a leaf.

The story of frog metamorphosis continues to be told year after year in schools and homes around the world.

In less than three months, almost anyone living near a pond or a wetland area, can watch as the four stage process that transform a tadpole into a frog.

Eggs
Tadpoles
Froglets
Adults

Females typically lay large jelly-like eggs masses in the nearby water. Depending on the species, the eggs can hatch into tadpoles in a time span ranging anywhere from a couple of days to a couple of weeks.

Tadpole development, the most visible part of the process, takes place entirely in the water.

Tadpoles move from a legless to leg stage, with the back legs the first to grow. Legs help tadpole propulsion in the water, enabling it to feed itself, mostly algae, and continue to grow.

Eventually, tadpoles begin to develop front legs and lungs to help with life on land.

Once developed, tadpoles, now commonly called froglets, begin their first investigations of land, shortly losing their tails and completing the cycle.

Non-native frog species, introduced through the pet trade, and released into wild, continue to attract attention.

Competition with the Cuban treefrog (Osteopilus septentrionalis) and Greenhouse frog (Eleutherodactylus planirostris), for example, introduced into Florida, might create stresses on native frog and toad populations.

Two types of Caribbean Treefrogs, the Coqui frog (Eleutherodactylus coqui) and the Greenhouse frog (E. planirostris), with established Hawaiian populations, cause concerns about their possible disruption of the Hawaiian ecosystem.

Around the world. disease and a changing climate also create stresses on frog populations.

The Global Amphibian Assessment (GAA), an ongoing research project sponsored by the International Union for Conservation of Nature (IUCN) and Conservation International (CI), shows population declines in many of the world's amphibian species.

A first of its kind report, the June 2007, the GAA listed a total of 5,918 amphibian species in the world.

Frogs and toads lead the list with 88% or 5,211 different species. Of those, 1,590 or 30.5% were listed as either vulnerable, endangered or critically endangered.

Salamanders and newts account for the second largest number of amphibian species with 535 or approximately 9% of the total. Of those, 249 or 46.5% were listed as either vulnerable, endangered or critically endangered.

Caecilians round out the list with 172 or a bit over 2% of the total. Of those, 5 or 2.9% were listed as either vulnerable, endangered or critically endangered.

The list is far from complete with little or no data on amphibian species entered for some states such as the Democratic Republic of Congo. Forthcoming data from other states such as Indian, Indonesia and Malaysia is anticipated to add to and alter the aggregate results. Therefore, current statistics need to be read as a first take comparative examination of global amphibian population trends.

Various reasons are given for population declines, with habitat loss cited as the primary causal factor. Amphibian population levels are exacerbated by two inter-related geographical factors. First amphibians are tied to both a specific geographical location and a specific habitat. Close to 90% of the world's amphibians live in a forest habitat. Global deforestation trends in the past couple of decades has contributed to declining amphibian populations.

Currently ten native frog and toad species are listed as either endangered or threatened under the terms of the Endangered Species Act.

Golden Coqui (Eleutherodactylus jasperi): Threatened
California Red-legged Frog (Rana draytonii): Threatened
Chiricahua Leopard Frog (Rana chiricahuensis): Threatened
Mississippi Gopher Frog (Rana capito sevosa): Endangered
Mountain Yellow-legged Frog (Rana muscosa): Endangered
Guajon or Puerto Rican Rock Frog (Eleutherodactylus cooki): Threatened
Arroyo Toad (Bufo californicus): Endangered
Houston Toad (Bufo houstonensis): Endangered
Puerto Rican Crested Toad (Peltophryne lemur): Threatened
Wyoming Toad (Bufo baxteri): Endangered

Another stress on frog populations, an amphibian skin disease called chytridiomycosis, caused by a chytrid fungus called Batrachochytrium dendrobatidis, Bd for short, takes on a sense of urgency as world wide frog populations continue to plummet.

Bd thrives in higher elevation, cool, moist habitats. In the United States, its presence has been most problematic in the Mountainous West, where a handful of species, including the Mountain Yellow-legged Frog population, an endemic species of the Sierra Nevada Mountains, have been affected.

East Coast frog populations, generally found in lower elevation, higher temperature habitats, have not been hard hit. Elsewhere, Bd outbreaks have caused severe stress on frog populations in Australia and Central and South America.

Recently a few, small research studies have shown promise for treating the fungus.

Chytridiomycosis in an aquarium collection of frogs: diagnosis, treatment, and control., reported that a small sample of frogs with Bd were cured following a treatment with an anti-fungal, itraconazole.

A March 2009 research report called Elimination of the amphibian chytrid fungus Batrachochytrium dendrobatidis by Archey's frog Leiopelma archeyi, showed positive results when using a topical anti-biotic called chloramphenicol.

Another March 2009 research report called Skin microbes on frogs prevent morbidity and mortality caused by a lethal skin fungus showed that the introduction of an "antifungal bacterial species, Janthinobacterium lividum" reduced mortality in a sample of Mountain Yellow-legged frogs.

While the research does not provide solutions for maintaining frog populations in the wild, they provide help for saving affected frogs in captive breeding programs. Further research might then provide avenues for neutralizing Bd in the natural environment, allowing for the reintroduction of healthy frog populations from the breeding programs.

Types of Frogs