• Frogs of the genus Mantella live on the island of Madagascar, off the eastern coast of Africa. Small and poisonous, they come in a variety of striking color combinations, including iridescent blues, oranges, yellows, and greens. The hard-to-miss colors serve as a warning to potential predators: Avoid me!

    Most mantella frogs secrete toxins through their skin, though a few species are nontoxic. The toxins aren’t strong enough to kill a predator such as a mammal, snake, or bird, but they will make it sick or at least leave a bad taste in its mouth. The frogs get these alkaloid toxins from their prey—primarily ants, termites, and other insects.

    All mantella frogs display bright colors. Some mimic the colors of more toxic relatives, a defense strategy called aposematism. The defensive colors wouldn’t be effective if they couldn’t be seen, so these frogs are active during the day, or diurnal. Most other frogs are nocturnal.

    Mantellas are small, usually about 5 centimeters (2 inches) long. They live among leaves, under decaying trees, or sometimes on low branches close to the jungle floor. They don’t need webbed toes for swimming the way most other frogs do. Their legs are also shorter than other frogs because mantellas climb more than they hop. Arboreal mantellas have flat, sticky fingertips that help them stay on branches when they are above the ground.

    Of the 16 mantella species, 11 are at critical risk, endangered, or vulnerable. Because they are so small and have skin that absorbs water, even small environmental changes could wipe out an entire species. That’s why climate change and pollution pose particular threats to mantella frogs. They are also threatened by habitat loss, introduced species, and collection for the pet trade. Mantellas have also been found to carry the fungus Batrachochytrium dendrobatidis, or Bd, which has infected and caused population declines in amphibians across the world.

    1. What adaptations do mantella frogs have to make them better suited to their habitat?

      Mantellas live among leaves, under decaying trees, or sometimes on branches close to the floor of the jungle, so they don’t need webbed toes for swimming the way most other frogs do. Their legs are also shorter than other frogs because they climb more than they hop. Arboreal, or tree-dwelling, mantellas also have swollen, sticky fingertips that help them hang on while climbing above ground.

    2. How might mantella frogs serve as indicators of the overall health of Madagascar’s environment?

      Tiny mantella frogs have porous skin, which makes them sensitive to changes in the environment. If mantella frogs are suffering, it suggests something in Madagascar’s rain forests, air, or waterways may not be healthy.

    3. Can human activity impact how toxic mantella frogs are?

      Yes, humans have an impact on how toxic the frogs are. In polluted areas, for instance, there are fewer prey species for the frogs, which means not as many sources of alkaloid toxins. In areas untouched by humans, mantella frogs tend to be more toxic.

  • Term Part of Speech Definition Encyclopedic Entry
    alkaloid Noun

    group of naturally occurring, organic bases containing nitrogen. Examples include morphine, quinine, and nicotine.

    aposematism Noun

    tactic where a prey species makes itself noticeable to predators, because it is toxic. Also called warning coloration.

    arboreal Adjective

    having to do with trees.

    climate change Noun

    gradual changes in all the interconnected weather elements on our planet.

    Encyclopedic Entry: climate change
    climate change Noun

    gradual changes in all the interconnected weather elements on our planet.

    Encyclopedic Entry: climate change
    convergent evolution Noun

    appearance of similar characteristics on organisms with different ancestors.

    defense Noun

    protection or resistance to attack.

    diurnal Adjective

    active during the day.

    endangered species Noun

    organism threatened with extinction.

    Encyclopedic Entry: endangered species
    habitat Noun

    environment where an organism lives throughout the year or for shorter periods of time.

    Encyclopedic Entry: habitat
    introduced species Noun

    a species that does not naturally occur in an area. Also called alien, exotic, or non-native species.

    iridescent Adjective

    displaying a wide range of colors that appear to shimmer and change depending on the angle of view or the angle of illumination.

    mimic Verb

    to copy another organism's appearance or behavior.

    nocturnal Adjective

    active at night.

    pollution Noun

    introduction of harmful materials into the environment.

    Encyclopedic Entry: pollution
    pollution Noun

    introduction of harmful materials into the environment.

    Encyclopedic Entry: pollution
    predator Noun

    animal that hunts other animals for food.

    prey Noun

    animal that is hunted and eaten by other animals.

    secrete Verb

    to discharge a substance.

    toxin Noun

    poisonous substance, usually one produced by a living organism.

    vulnerable species Noun

    level of conservation between "near threatened" and "endangered." Vulnerable is the lowest of the "threatened" categories.