What do “green and slimy”, a Muppet, and Prince Charming all have in common? Frogs of course! When someone hears the word “frog” there are any number of images and associations that could come to mind, so it should come as no surprise that frogs themselves show a great deal of diversity. With nearly 5,000 different species, Anurans, or frogs and toads, can be found on six continents ranging from the tropics to the subarctic. At the DWA you can find frogs and toads on exhibit from Central and South America, Mexico and even Madagascar. The stunning Red-eyed tree frog (Agalychnis callidryas) in the Mundo Maya Exhibit, with its vibrant coloration, delicate locomotion and prominent red eyes has become a symbol of not only Central America but of rainforests and the tropics in general. But dig a little deeper and you’ll find that there are many other amphibians to be found — each unique and beautiful in their own way.
One Environment: Two Adaptations
As you make your way through the Rainforest, the first amphibian you will come across is the stoic Waxy monkey frog (Phyllomedusa sauvagii), a nocturnal tree frog native to the Gran Chaco, an area of dry, scrub forests in Argentina, Bolivia, and Paraguay. Like other amphibians, these frogs have permeable skin which could be a real threat living in a dry environment. However, they have developed a way to reduce water loss through their skin. They possess a specialized gland which secretes a lipid that they then coat over their bodies using their legs. These lipids contribute, as their name suggests, to their waxy appearance.
Moving through the Rainforest to the River Gallery you will find another frog from the Gran Chaco region of South America – Budgett’s frog (Lepidobatrachus sp.). Where the Waxy monkey frogs have adapted to life in the trees, the Budgett’s frog thrives in a more aquatic environment. Equipped with webbed feet, this frog will often be found sitting in pools of water or burrowed in the mud. At first glance it may appear that there is nothing but rocks on the bottom of the exhibit but look closely and you’ll notice that one of the large gray-green “rocks” has a pair of eyes! They are ambush predators and will often sit perfectly still in either mud or water waiting for their prey. Much like their relatives, Ornate or “Pac-Man” frogs, they have disproportionately large mouths, which allow them to prey upon insects and animals much larger than other frogs their size.
Bright Color, Bad Taste?
In Madagascar, there are two different species of frogs that showcase the vibrant pigmentation associated with aposematism, or warning coloration, found in many amphibian species. The Golden mantella (Mantella aurantiaca) is a golden-yellow terrestrial frog that can be found in the higher elevations of Madagascar. A relatively small frog, adults only get to be about 1-1¼” long. As their skin color suggests, these frogs are toxic and they use their bright colors to advertise to potential predators that they won’t make a very good meal. While less toxic than the dart frogs of South America, the mantellas do produce enough toxin to give themselves an unpleasant taste and in some cases, the ability to make their predators sick.
Across from the Golden mantella you will see the Tomato frogs (Ambystoma mexicanum), which as their name suggests, are red. They inhabit moist forests and swamps and are more robust than the little mantellas. Adults can be up to four inches long, but when threatened they will puff themselves up, making them appear larger. In addition to inflating their bodies, as a form of defense, Tomato frogs can produce a substance that will gum up the eyes and mouth of a predator. While the substance isn’t fatal, the reaction will often cause the predator to release the frog, allowing it to escape.
One Extreme to the Other: Endangered and Invasive
Amphibians are often considered to be “bioindicators”, with the overall health of an environment being directly correlated to the overall wellness of the amphibian population. As previously stated, amphibians have permeable skin. They literally act like little sponges in their environments, making them more susceptible to chemicals and toxins. It should be cause for concern that one-third of the world’s amphibian species are currently at risk of extinction as a result of pollution, habitat destruction, climate change and disease. The DWA is home to critically endangered Panamanian golden frogs (Atelopus zeteki), which are potentially extinct in the wild largely due to the “chytrid” fungus epidemic that devastated wild frog populations. Prior to the chytrid outbreak, wild individuals were removed to captive breeding institutions to help safeguard the species from extinction. On exhibit in Mundo Maya you will find 30 Panamanian golden frogs which were born and raised here at the DWA.
At the other end of the shark tunnel you will find another member of the Family Bufonidae, Bufo marinus – or the Cane toad, a species whose history couldn’t be more different. Where resources are being pooled to help save the Panamanian golden frog and other species from extinction, governments and scientists are working to eradicate Cane toads around the world. Originally found from South Texas through northern South America, Cane toads were introduced to Florida, Australia, the Caribbean and many areas in the South Pacific from the 1930s-1950s as a form of agricultural pest control. The toads were intended to feed on insects that were threatening plantation crops, namely sugar cane. The success of the toads in safeguarding the sugar cane varied by location, but the toads began to flourish in many of their new environments. Over time, as their populations expanded, these toads began to threaten native populations and impact biodiversity. Gregarious in nature, the toads threaten other species by predation or by out-competing them for resources, while they themselves are highly toxic and can be fatal to both wild animals and domestic pets.
In 2008, we celebrated the “Year of the Frog” and introduced the “Frog Car” that you see parked in the lot across from the aquarium – still a favorite photo op for many guests. Five years later, amphibian awareness remains at an all-time high, largely as a result of the educational initiatives and exposure provided by zoos and aquariums around the country. So as you make your way through the aquarium, keep your eyes open for these frogs as well as many other fascinating amphibians we have on display.