Some plants, animals use poison to protect themselves

You wanted to know

"Why are some frogs poisonous, and why are some plants or animals poisonous at birth?" Two curious readers, a young Wauconda Public Library patron and a student in Gregg Thompson's sixth-grade social studies class at Woodland Middle School in Gurnee, wondered about frogs, plants and poisons.

You are what you eat, the saying goes. This is especially true for certain dart and arrow frog species.

The mother frog dines on ants and termites that are loaded with batrachotoxin, an alkaloid that causes brain and muscle damage and paralysis. She then feeds her tadpoles unfertilized eggs that carry the toxin. The poison is absorbed into glands under their skin, with no effect to the baby frogs. But predators beware; one bite of the multicolored, minuscule frog can kill up to 10 adults.

The brightly colored ½-inch to 2-inch-long amphibians are known in their rain forest community to be deadly, so most predators stay far from away them, except for the fire bellied snake, said Andy Snider, curator of herps and aquatics for the Chicago Zoological Society, which operates Brookfield Zoo.

Dart frog colors reflect an incredible range of hues, including strawberry, blue, yellow-banded, green-and-black, white and golden. The amazing color schemes have been adopted by nonpoisonous frogs, an adaptation called mimicry, so predators are tricked into thinking that all colorful frogs should be avoided. Actually, only three species of dart frog carry the poison.

Snider has seen these little colored frogs in the rain forests while on trips to Peru, Costa Rica and Panama. Visitors can appreciate these beauties at Brookfield Zoo's Reptiles and Birds habitat, home to a number of dart frog species. No worries about the poison, though. The toxicity only lasts as long as the frogs continue to consume a diet of insects with toxins.

"When bred in captivity, they don't retain the toxin because they aren't eating the ants and termites," Snider said.

There's toxic and there's poisonous. A toxin is naturally produced and causes harm under certain, not all, situations. Poison is naturally or chemically produced and can be deadly.

Venom, produced in nature, refers to how poison is delivered, like the venom from a snake bite or wasp sting. Many plants have toxic parts, like apple seeds or apricot leaves.

What plants and animals have in common, in this instance, is the use of poison to keep predators at bay. Most likely, the ants and termites eaten by poison dart and arrow frogs draw their toxins from plants.

Plants need to fend off a host of predators: insects, bacteria, animals, people and even other plants. They've developed a range of strategies, including rough, spiky, hairy or hard coverings like bark and seed shells; bitter flavors; nutritional values that can plummet under certain circumstances; chemical mimicry; and toxins.

Even brushing up against a plant can cause skin to burn or blister, like contact with poison ivy or oak. According to the Iowa National Heritage Foundation website, scientists have discovered more than 10,000 alkaloids in plants, including caffeine, nicotine, and highly toxic alkaloids like strychnine. If a plant causes harm, call the Poison Help Line at (800) 222-1222 to receive help 24/7.

Some plant toxins are used to treat illness. The seeds, leaves and bark of the Pacific yew are toxic, and have been successfully applied to treat certain cancers. Digitalis, from the foxglove plant, can be fatal. It's the source of medicine used for congestive heart failure.

Frog and reptile fans can learn more about these animals when they join the Chicago Herpetological Society Jr. Harpers. Young frog fans ages 5-8 can register for one of Brookfield Zoo's "Life at the pond" sessions June 16 or 23.

Gardening classes for kids and their families are held at the Morton Arboretum in Lisle, Cantigny Park in Wheaton and the Chicago Botanic Garden in Glencoe. See the organization's websites for more information.

Check it out

The Wauconda Public Library suggests these titles on poison dart frogs:

• "Deadly Poison Dart Frogs," by Jennifer Dussling

• "Poison Dart Frogs," by Jennifer Owings Dewing