Protected by a cloak of color
Poison frogs are wildly colored, their flamboyant “attire” a warning to predators that they are a dangerous dining choice.
BY Karyl Carmignani
Photography by Ken Bohn
Bright as baubles from a fairy tale, these energetic little hopping gems dot the hot, damp forests of Central and South America. But there is nothing “happily ever after” for predators of these vividly colored amphibians; the 300 or so Dendrobatidae species of poison dart frog exude toxins from their skin that can deter or destroy an enemy on contact. While only a few species pose a threat to people, the prince of poison is the golden variety, which carries enough toxicity to kill 10 grown humans, making it the most poisonous animal on the planet. But, as Erika DiVenti, senior reptile keeper, explained, “Poison frogs are less toxic in the Zoo. That may be because they are eating different arthropods—and those arthropods are eating different plants—than they would in the wild.” During digestion, the frog is able to “manufacture” toxins in poison glands just under the skin by utilizing the different chemicals in its prey items. These tiny, boldly behaving, diurnal frogs are termed aposomatic—advertising their danger to predators with their badge of bright colors. Other non- or less-toxic species piggyback on this defense strategy, mimicking their coloration to also deter predators. For predators, it is a cautionary tale.
Hunting for the Right Name
Resourceful hunters from various indigenous tribes throughout the frogs’ range have used the poison from the frogs on their blowpipe darts and arrow tips, so the animals were aptly named poison arrow frogs or poison dart frogs. One method of extracting poison was piercing the one-inch-long amphibian with a stick, causing the animal a great deal of stress, and triggering a foamy froth of poison to form on its back, which the hunters could then dip their weapons into. Even a year later, the batrachotoxin poison could cause paralysis and death in the monkeys and birds they were hunting. Fortunately, the gruesome practice of goring the frogs for their poison is waning, so much of the current literature refers to the colorful creatures as simply poison frogs. Others insist that poison frog is a more accurate name for the group, since only about three species of the Dendrobatidae family are used to poison arrow tips: Phyllobates terribilis, P. bicolor, and P. aurotaenia.
Secrets of Secretions
Each species of poison frog produces a different blend of alkaloids and other chemicals that make up its signature poison and level of toxicity. The three most toxic species all inhabit Colombia. Scientists have been investigating ways these wildly noxious substances might possibly be used in the medical field. Some poison frog alkaloids have been found to help people with certain heart and circulation problems. And the endangered phantasmal poison frog of Ecuador produces a toxin called epibatidine, which can block pain 200 times more effectively than morphine and without the pesky side effects. Though it is barely one inch long, this strikingly striped frog packs a medicinal punch!
One of the most unusual behavioral characteristics in the Dendrobatidae family is the level of parental care doled out to the offspring. While it varies somewhat between species, for many of the vibrantly colored poison frogs, the male frog entices the female with an ardent call to a leafy, covered, humid spot on land where she deposits her eggs in a gelatinous mass.
Once they develop into tadpoles, one of the parents will “shuttle” the little ones to a suitable body of water, such as a secluded puddle in a bromeliad. In some species the male protects and nurtures the eggs and newly hatched tadpoles, while in others mom does the doting. The female has the presence of mind to lay extra eggs, which are laden with poison, to feed to her tadpoles, who then become poisonous themselves—a handy defense when you’re the size of a Tic Tac®. Once a youngster has absorbed its tail and developed into a tiny replica of its parents, it is free to hop around in search of insects.
Poisonous vs. venomous, it’s all in the delivery! Poison frogs are not venomous because they don’t bite you like, say a snake, to inject venom. These frogs are passively harmful, with poison on the outside activated upon ingestion; venomous animals inject their poison into the bloodstream via fangs or spines.
Labor of Love
For reptile keepers like Erika, every day is different. “Cliché as it sounds, it really is a labor of love.” She explained how the poison frogs on exhibit in Reptile Walk have little habitats that provide great viewing for the guests while also containing features that the animals seek in the wild, like a moist, secure place to lay eggs. Each day, Erika checks the shallow dish with a cover of bromeliads for miniature eggs. “The male frogs carry the young, so sometimes that’s how we find them,” she added.
The babies look different from the adults and they are too tiny for a microchip, so keepers identify the young in their records with pictures or drawings, as they change and develop so rapidly. Erika explained that the tadpole holding rack located behind the scenes has filtered, temperature-controlled water with many sensors, and a backup generator to ensure the well-being of the frogs. Later, when the frogs have grown legs, they move to a morphing tank, which is half water and half land. Here they “absorb their tail and don’t eat much,” Erika said, “a process that takes a week to a month, depending upon the species.” It is next to impossible to sex the miniature frogs, as males and females look the same. But sometimes, like when the air pressure changes, a male juvenile will start to call and its throat pouch enlarges, which reveals its gender. “We sex them by call, not by looks,” Erika succinctly observed. The poison frogs soon graduate to a small tank, and finally a large, communal living arrangement, where they can live up to 15 years.
Hop over to the Zoo’s Reptile Walk and feast your eyes upon our amphibian jewels: bumblebee, green-and-black, splash-back, dyeing, and black-legged poison frogs are all on display. Look, but don’t touch!