Rain forest

Poisonous jewels of Madagascar

Tiny mantella frogs are among the most brightly colored and spectacular of all frogs. Most can be found in a variety of color combinations—inky black with brilliant splotches of orange, bronze, yellow, blue, or emerald green. These bright, eye-catching colors serve as a warning to predators that the little frogs are poisonous.

A toxic meal

Mantellas are found only on Madagascar, an island nation off the eastern coast of Africa. Many mantella species secrete toxins like those found in South America's poison frogs. They get alkaloid toxins from the prey that they eat, primarily ants, termites, and fruit flies. They then use these toxins for their own chemical defense. While not deadly like the golden poison frogs, mantellas secrete enough toxins to make a predator sick or, at the very least, the little frogs can make themselves taste quite nasty!

Interestingly, human actions can affect how toxic mantellas might be. For example, mantellas living in areas untouched by human activity have more alkaloid toxins in their bodies than those living in areas that have been polluted. Why? As humans move into mantella habitat or pollute it with contaminants, many of the frogs' prey items are killed off, and there is less variety for the mantellas to eat. Fewer food choices mean fewer alkaloids to be absorbed which leads, eventually, to less toxic frogs.

For many years, scientists believed that Madagascar’s mantellas and South America's poison frogs were closely related. But DNA studies have shown that they are only distant relatives with similar bright, warning colors.
Scientists have only recently discovered that some mantellas have skin toxins.
A group of mantellas is called an army.
The golden mantella is the most well known of the species. Individuals can be yellow, bright orange, or orange-red in color.
The variegated mantella lives in the high grasslands of Central Madagascar. It burrows during the dry season to keep from drying out.

The San Diego Zoo began exhibiting mantellas in the late 1980s and has successfully bred and maintained the critically endangered golden mantellas and bronze-backed mantellas. Our new Reptile Walk, which opened July 2012, features reptile, amphibian, and California native species exhibits. It is located in the Discovery Zone, just across from our Galápagos tortoise exhibit, and includes golden mantellas and bronze-backed mantellas as well as poison frogs, newts, and other fascinating amphibians.

Like all amphibians, mantellas have skin that soaks up water. If something happens to change the water, amphibians are one of the first species to feel it. Much like frog species from all over the world, the health of mantellas can help scientists determine the health of Madagascar’s rain forests, air, and waterways. Because mantella populations are small, the slightest problem or mildest pollutant could be enough to completely wipe out a species.

Eleven mantella species are either at critical risk, endangered, or vulnerable. Threats to these delicate frogs include habitat loss, contaminants, introduced species, global climate change, and collection for the pet trade. Some species, like the golden mantella, live only in tiny, limited areas, making them sensitive to over collection by people wanting to have the colorful frogs as pets. The San Diego Zoo is involved in breeding two mantella species to learn more about them and to help preserve these jewels of the rain forest for future generations.