Amphibia

Axolotl

Axolotl, Ambystoma mexicanum

This Mexican relative of the Tiger salamander keeps its external gills throughout life, making it a classic example of the retention of juvenile features into adulthood (technically known as paedomorphism or neoteny). Now critically endangered, since most of its former habitat is occupied by Mexico City, it was an important food for the Aztecs, whose name for it translates as “Water Dog”. First brought to Europe in 1863, it became an important experimental animal in laboratories, where an albino mutation was established.

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Hourglass tree frog

Hourglass tree frog, Dendropsophus ebraccata

While “hourglass” is fairly descriptive of the pattern on the back, as with human fingerprints and zebra stripes, each frog has its own unique set of markings, unless, as is sometimes the case, it has no pattern at all. This species occupies a range of habitats from Mexico down into northern South America. Like its much larger relative, the Waxy monkey tree frog, it can lay its eggs above water, into which the tadpoles fall after they hatch. However, if there is little or no shade, it may lay its eggs in the water like most frogs. It is the only frog that can do both.

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Panamanian golden frog

Panamanian golden frog, Atelopus zeteki

Actually a toad, it is known only from Panama, where it has been protected by a Decree of the National Legislation since 1967. It was originally threatened by habitat destruction and over-collecting by animal dealers, but the much-publicized outbreak of a chytrid fungus in amphibian populations has had a far worse effect. Since 2007, none have been seen in the wild. They breed well in captivity. Over a thousand are distributed among many US zoos and more are maintained in Panama. Though venomous, it is not related to dart frogs.

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Red-eyed tree frog

Red-eyed tree frog, Agalychnis callidryas

For years this amphibian was known either as a spectacular subject of photos, or as a lump-like creature, fast asleep while stuck to a leaf or the wall or glass of its exhibit. Experiments with lighting at the DWA have resulted in increased activity, so that the startling red eyes and beautifully patterned legs and flanks are more likely to be appreciated. Found from Mexico to Northern Colombia, this is another frog that lays its eggs on leaves above water, into which the tadpoles fall.

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Marine toad

Marine toad, Bufo marinus

The infamous Australian Cane toad was originally native to Tropical America, from South Texas to the Amazon Basin. It can exceed five pounds in weight and attain a snout-vent length of more than a foot. Because of its voracious appetite, it was introduced to tropical places around the world to control sugar cane pests. Initial successes in Puerto Rico encouraged introductions elsewhere, with disastrous results. Both tadpoles and adults are highly toxic, causing the decline of predatory reptiles, not to mention small prey species.

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Tomato frog

Tomato frog, Dyscophus antongilii

As with many other brightly-colored amphibians, the color of this frog indicates it can secrete an unpleasant substance when seized, in this case a thick, mildly toxic mucous. Found in a variety of habitats all over Madagascar, it has been a popular zoo animal since the 1970s, and is frequently bred in captivity. Females are larger and more colorful than males, and can reach four inches in length.

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Waxy monkey tree frog

Waxy monkey tree frog, Phyllomedusa sauvagei

This inhabitant, of the dry Chaco forests in Southeastern South America, has developed some decidedly unfrog-like behaviors. Instead of laying its eggs in water, it builds a nest above it, laying eggs on a leaf, which it folds around them. There the tadpoles hatch, then fall into the stream below. It smears its body with wax secreted out of its own skin, using complicated maneuvers of its hind legs. Its unusually expressive appearance has made it popular in zoos, and it is now captive-bred in increasing numbers.

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Yellow-banded dart frog

Yellow-banded dart frog, Dendrobates leucomelas

Since “leucomelas” means “white and black” in Greek, it is likely this scientific name was assigned on the basis of colorless museum specimens, preserved in alcohol. In life, these frogs are bright orange-yellow, with black bands or stripes. Like other dart frogs, wild ones, which are poisonous, but captive animals kept on a diet of fruit flies and crickets largely lose their toxicity. This species comes from Venezuela and adjoining areas of Northern South America.

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Aquatic caecilian

Aquatic caecilian, Typhlonectes natans

Very few of the 180 or so caecilian species are easily exhibited in zoos or aquariums, as most live underground. This South American species is an exception, living in water instead. It has been bred in captivity, including the DWA, giving birth to live young. Confined to parts of the Old and Near World Tropics, caecilians compose one of the three orders of amphibians (the other two being frogs and toads, and salamanders). They are the only living amphibians with scales, but these are hidden beneath their skin.

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Blue poison dart frog

Blue poison dart frog, Dendrobates azureus

When these amazing frogs first appeared in zoos in the 1970s, they created a sensation and remained very rare in collections until the mid-1980s. They are now widespread in captivity, thanks to their popularity. As with other poison dart frogs, captive-bred animals raised on fruit flies and crickets lose their toxic qualities. Found only on a few “islands” of forest, arising out of the Sipaliwini savannah of Suriname and Brazil, they are considered vulnerable to extinction, so that their status as a self-sustaining captive population is especially satisfying.

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