Tree frogs have special suction pads on their feet that let them climb almost anything. Photo courtesy Al Walters.
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Tree frogs have special suction pads on their feet that let them climb almost anything. Photo courtesy Al Walters. |
Amphibians include frogs, toads, and salamanders. These animals are normally thought of as aquatic, but they do inhabit forests in both temperate and tropical regions. Salamanders, with their long, thin bodies, are sometimes confused with lizards, but lizards are reptiles. Amphibians have smooth, scaleless skin and toes without claws, while reptiles are distinguishable by their rough scales and claws. |
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Amphibians are limited in where they can live because they need access to pools of fresh water in which to lay their eggs. Although some amphibians can spend their entire adult lives on dry ground, all of their eggs need to be laid in the water. All amphibians, like insects, go through a complete metamorphosis between their larval and adult stages. Amphibians begin their lives in the ponds where they hatched from their eggs. Sometimes these ponds are tiny pools of water between the leaves of a plant, or they are large expanses of wetlands within the forest (riparian zones). The small, aquatic tadpoles you can try to catch from ponds in the spring eventually grow legs and mature into frogs. The complete metamorphosis of amphibians allows them to take advantage of two separate habitats during different stages of their lives. Metamorphosis is much more common in insects than in vertebrates. |
| Temperate woodland salamanders are nocturnal and usually take shelter under logs and rocks. This makes them rather difficult to observe. Salamanders are also completely quiet, making no vocalizations at all which could indicate their presence. The red-spotted newt has a different pattern of metamorphosis than the other amphibians. It has an aquatic larval stage, which is normal for amphibians, but it is also aquatic as an adult. In between the larval and adult stages is a terrestrial juvenile stage. The red-spotted newts change from being aquatic larva to being terrestrial "red efts", which is the name for animals in this juvenile stage. Individuals can remain in this intermediate terrestrial stage for up to nine years, before undergoing metamorphosis again and becoming aquatic adults. |
Salamanders live in shady areas where they can stay moist at all times. Photo credit Corel Photo Clipart CD. |
| Many salamanders have another unusual feature: they live on land, they breathe air, but they have no lungs! These animals live in moist, shady areas near ponds or other sources of water. They usually remain under leaves and decaying wood, and avoid staying anywhere open and dry. | Their skin has to remain moist at all times, because this is how they breathe. The moist skin of these lungless salamanders works as a membrane for gas exchange, but if the skin dries out, air can no longer move through it. The lungless salamanders suffocate if their skin doesn't remain moist. |
| While salamanders try to remain hidden, frogs and toads tend to stay more in the open and are easier to find. Although they are often camouflaged, they are also easier to observe because they usually remain calm when approached by a person, rather than panicking, attacking, or fleeing, which are much more common behaviors among vertebrates. |
 A Pacific tree frog navigating a tricky terra-cotta pot. Photo by Maya Walters. |
Frogs and toads are well known for their often loud vocalizations. Each species has a distinct call, and during their mating season, many will often be calling simultaneously. The distinct calls help males and females of the same species find each other. Some calls are used as territorial signals, but most are used only for attracting a mate. |
| There are many predators that specialize in eating frogs. Snakes, bats, fish, hawks, herons, almost all carnivorous mammals, and many other animals feed on frogs. Even some frogs feed on other frogs. Some frogs are nocturnal, which helps them avoid certain predators, and some have chemical defenses--substances which make them taste unpleasant or even make them toxic to predators. |
| Certain frogs have evolved complex behavior to help their tadpoles survive. In the tropical rainforest, some poison arrow frogs actually do not lay their eggs in ponds. Instead, they are laid on a leaf and the male incubates them on the forest floor for several weeks until they hatch. The newly hatched tadpoles then hang onto the back of the female frog, who distributes them in pools of water collected in the leaves of bromeliad plants. Usually she leaves only one tadpole in each plant, increasing their chances of survival. She later returns and lays several unfertilized eggs in each pool, which the tadpoles eat. |
 A Pacific tree frog perched on a leaf. Photo by Maya Walters. |
 Pacific tree frog. Photo by Maya Walters. |
Unique, unusual behaviors such as those of the poison arrow frogs described on the previous page are much more likely to occur in the tropics. In the temperate zone, most frogs behave in very similar and more predictable ways. In the tropics, however, there are not only more varied habitats and more opportunities for specialized behavior, there are also more frogs. The entire United States is home to only 80 species of frogs, while Ecuador, a South American country smaller than the state of Nevada, has over 300 frog species. |
 Many frogs live near shallow wetlands, which are perfect tadpole habitat. Photo by Maya Walters. |
related topics
[reptiles] [riparian zones] [mammals] [fish] [birds] [camouflage & chemical defense] [temperate forests] [tropical forests] [biodiversity]
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