The Bombinatoridae is a family of toads consisting of eight species in a single genus, Bombina. They are commonly referred to as the "firebellied toads", due to the bright colors on their bellies. Firebellied toads are distributed across Europe and Asia. The Oriental Fire-Bellied Toad is commonly found in the pet trade, and can be purchased in pet stores across much of the United States.

Bufonidae

The members of the family Bufonidae are often known as the "true toads". Over 600 species are found in this group, and their natural distribution includes North and South America, Europe, Africa, and Asia. One member of this group, the Cane Toad (Rhinella marina) has become an invasive species after being introduced to Australia, Hawaii and elsewhere.

Although the Bufonidae look similar to Fire-Bellied Toads and Spadefoot Toads, they are only distantly related to these groups. In fact, the true toads are more closely related to the treefrogs (Hylidae) and true frogs (Ranidae) than they are to the Fire-Bellied Toads or Spadefoot Toads.

Many of the true toads used to be assigned to the genus "Bufo". However, in 2005 a group of amphibian taxonomists proposed re-arranging the taxonomy of many amphibians, including toads. Although many of the proposed taxonomic changes are controversial, many of the changes to true toad taxonomy appear to have been accepted by much of the research community. Many of the North American toads pictured below were formerly assigned to the genus "Bufo", but are now separated into various other genera such as "Anaxyrus" and "Incilius".

American Toads (Anaxyrus americanus) are found across much of eastern North America. Adults migrate to wetlands in the spring, where males attract females with their distinctive, extended trilling call. The American Toad mating season is a hectic event, with males singing and fighting as females enter the ponds to mate. In some years and some locations, female toads are more likely to mate with larger males, however this is not always the case. There is some evidence that female American Toads prefer males that have a high rate of calling, or lower-frequency ("deeper") trills.

Hylidae

The Hylidae are a diverse group of treefrogs, with nearly 1,000 species distributed on all continents except Antarctica.

In the continental United States and Canada, there are three genera of native treefrogs: Acris, Hyla, and Pseudacris. The Cuban Treefrog has been introduced to the US and become established, adding a fourth genus: Osteopilus.

Spring Peepers (Pseudacris crucifer) are one of the best-known harbingers of spring in eastern North America. They are one of the first frogs to call as snow changes to rain, and their loud "PEEP!" can be amplified by hundreds or even thousands of male peepers calling from wetlands. These small frogs are usually some shade of tan, and can be distinguished by the "X" marking across their back. Spring Peepers metamorphose at a tiny size, and can easily fit on top of a penny. Outside of the breeding season, Spring Peepers typically live in forests, and often can be found on damp days hopping around the forest floor.

Pacific Chorus Frogs (Pseudacris regilla) are widespread in western North America, and famously appear as frog sounds in Hollywood movies and even popular music. Within their native range, Pacific Chorus Frogs can be found in a variety of habitats, including in eagle nests high in trees. These frogs sometimes are carried outside their native range on agricultural products like Christmas Trees. There is an entire page dedicated the the biology of Pacific Chorus Frogs.

Midland Chorus Frogs (Pseudacris triseriata) are found through much of Michigan, Ohio and Illinois, with some distribution into surrounding states. In much of their range, they are one of the first frogs to begin calling every year, along with Spring Peepers and Wood Frogs. Their call is a clicking trill, reminiscent of the sound made when you rub a finger along a comb.

Green Treefrog (Hyla cinerea) are found in much of the southeastern United states from Texas through Maryland. Male Green Treefrogs have an interesting (some would say "amusing"; others would say "annoying") honking call.

There are two species of Gray Treefrog in North America: the Cope's Gray Treefrog (Hyla chrysoscelis) and the Gray Treefrog (Hyla versicolor). These two species are found across much of eastern North America, and they cannot be told apart by their physical appearance. They differ in how many chromosomes they have. Cope's Gray Treefrog is diploid with 24 chromosomes, and the Gray Treefrog is tetraploid with 48 chromosomes. The Gray Treefrog originated as a new species through polyploid speciation when an ancient event caused a doubling of the number of chromosomes in Cope's Gray Treefrog. These two species can be told apart by the males' call. Cope's Gray Treefrog calls are a more rapid trill than those of the Gray Treefrog.

The Cuban TreeFrog (Osteopilus septentrionalis) was introduced to the United States from Cuba at least as early as the 1920s, if not earlier. They are frequently moved around in horticultural material. While they are impressive-looking treefrogs, they can harm native amphibians and other animals.

Ranidae

The family Ranidae is composed of over 400 species with a nearly worldwide distribution. In North America, these can be thought of as our "typical frogs" or "water frogs", although some of them spend most of their lives away from water. Here, I use the genus "Rana" for all of our North American ranid frogs. However, the taxonomy of these frogs was thrown into chaos in 2006 when a group of amphibian biologists published a 371-page paper that re-arranged the taxonomy of many amphibians. This was a controversial opinion, with many criticisms of the methodology. In 2016, another group of researchers conducted another analysis of the evolutionary history of the amphibians, and argued for the restoration of the genus "Rana" for North American members of Ranidae. Following this more recent research, and consistent with amphibiaweb, I will use the genus Rana rather than Lithobates.

Green Frogs (Rana clamitans) are found in much of eastern North America. They are one of our larger frogs, but don't get as large as American Bullfrogs.

Greenfrogs have a distinctive call like the sound of someone plucking a banjo string. I think of their call as one of the sounds of summer. From May through August, day and night, I regularly hear the twang of the Greenfrog's call when I am near wetlands in the midwest.

A male Greenfrog's vocal sac inflates as it calls.

An example of the generalist nature of green frogs, this video shows an adult green frog hanging out in a vernal pool eating wood frog tadpoles. One of the interesting aspects of this is that green frogs typically don't breed in these kinds of vernal pools. Because these pools dry out every year, and green frog tadpoles typically take at least a year to metamorphose, any green frog eggs laid in this pond would not survive to metamorphosis. Yet green frogs still visit these vernal pools to feast on the wood frog tadpoles.

American Bullfrogs (Rana catesbeiana ) are native to eastern North America, but have been introduced to other parts of North America and around the world (e.g., Africa, Asia, Europe). They get very large, and their prey includes insects, birds, mammals, reptiles and other amphibians. Their large size and hearty appetites combine to cause problems for native species.

Bullfrog females can lay over 20,000 eggs. In very warm weather, their tadpoles can metamorphose within a year. But in cooler environments, including much of their native rage, the tadpoles will usually take one or two years to metamorphose. Thus, the tadpoles spend at least one winter in ponds, sometimes two. Their tadpoles are also distasteful to fish, allowing them to co-exist with fish when many other amphibians can't.

Pickerel Frogs (Rana palustris) have a patchy distribution throughout much of eastern North America, with large gaps in some regions. They often breed shortly after the wood frog breeding season, but before many of the summer-breeding frogs, like bullfrogs and green frogs.

The Northern Leopard Frog (Rana pipiens) is one member of a group of leopard frog species. It is similar in appearance to the Pickerel Frog, but the spots on its back are more irregular in appearance. It also has an early breeding season, and its tadpoles metamorphose after a couple months.

Close-up of hatchling wood frog head.

Scaphiopodidae

The family Scaphiopodidae is confined to North America, and contains seven species spread across two genera: Spea and Scaphiopus.