Learning basic frog identification skills can be a fairly straight forward task for people of any age. Starting with a big picture look at the frog world, scientists organize the approximately 5,000 different types of frogs and toad species into twenty-five families. The ninety North American species span nine families.
Fortunately, for frog identification purposes, approximately eighty per cent of the frog species in the United States fit into one of three families: true frogs (Ranidae); tree frogs (Tree Frogs) and true toads (Bufonidae). The types of frogs presented here follows that three family framework. Generally a few species such as the bullfrog, pictured at the top of the page, have a range that extends across the United States. The remaining species have more geographically limited ranges based on either east-west or north-south general divisions.
In addition to the bullfrog, approximately two dozen more regionally based (Ranidae) species make their homes in ponds, streams and other slow moving water bodies. Red-legged frogs provide a good example of an east-west frog division. Two species live in slow moving water areas of the west. Once abundant throughout the state, the California Red-legged frog population decreased over 90% and was listed as an endangered species list in 1996. The remaining population now survives primarily along California’s coastal areas, where they still compete for territory with California’s coastal loving human population.
Northern Red-legged frogs (Rana aurora) inhabit coastal and inland areas of the Pacific Northwest from northern California to British Columbia. They prefer slow moving or still, shallow water habitats for breeding. During non-breeding season their range extends to many of the nearby forest floors. While they are not listed as endangered, their populations have declined over the years due to habitat destruction and habitat competition with the larger and more aggressive Bullfrog.
Rana species with large green frogs with spots and dorsal ridges along the sides of the body generally get categorized by the name Leopard Frogs. They inhabit many water habitats across North America and Central America, accounting for their nicknames such as meadow frog and grass frog.
Once believed to be a single species, scientific research, especially DNA analysis, now suggests the existence of anywhere from twenty to thirty different leopard frog species. In areas where species overlap, hybridization can also occur. The Northern Leopard Frog (Rana pipiens), probably the most widespread of the species, inhabits areas across most of the northern United States and southern Canada. Rana pipiens also now serves as the benchmark for organizing scientific thinking on all leopard frogs, which now get grouped into what is called the Rana pipiens complex.
On the other hand, consider the Pickerel Frog (Rana palustris) in the picture. They also have a spotted body and therefore can easily be confused with the Leopard Frog in areas where their ranges overlap.
Types of Frogs: Tree Frogs
Many of the native treefrog species build strong regional identities. The Eastern Gray Treefrog (Hyla arenicolor), for example, inhabits slow moving water areas near forests in much of the areas eastof the Rocky Mountains that provides suitable habitat. Like many tree frogs, their skin color varies from green to gray to brown, and it generally serves as an effective camouflage against predators.
The Pacific Tree Frog (Hyla versicolor), a small frog found in ponds and other small watering holes throughout the West Coast, is well known for its vocalizations. Sometimes called the Pacific Chorus Frog, they can really croak up a symphony of sound during the night hours.
Much like the chameleon, Pacific Tree Frogs adopt a variety of colors depending on environmental factors such as background light. It’s not unusual to see their skin change from green to brown to rust, and any combination, in a matter of hours.
In 2007, Washington State designated the Pacific chorus frog its official state amphibian.
The Canyon Tree frog (Hyla arenicolor) inhabits the rivers and stream banks of rocky areas in the desert Southwest. Their diet consists of the aquatic and terrestrial insects in their territory.
The Cuban Tree Frog (Osteopilus septentrionalis), a non-native species, was introduced to Southern Florida in the early Twentieth Century. It has subsequently expanded its territory to include most of the Florida peninsula.
Cuban Tree Frogs also rank as the largest tree frog species in the United States, and their presence in Florida continues to stress some native tree frog species. They range in color from the light tan specimen in the top picture, to a darker shade of spotted green.
Most practice nocturnal behavior, sleeping in trees and shrubs during the day and perching on walls and ceilings during the warn night hours.
An east-west division of native toad species also grounds the current identification discussion. The boreal or western toad (Anaxyrus boreas) shown in the picture, for example, can be considered the dominant regional toad species on both sides of the Rocky Mountains. However, it’s eastern range stops where the plains states begin.
Compare the less warty body of the Eastern Spadefoot Toads (Scaphiopus holbrookii). It’s the only spadefoot species that lives east of the Mississippi river, and it follows the general identification rule of thumb for spadefoot toads having relatively smoother skin.