Re: are the tadpoles of poison dart frogs poisonous?

The short answer is, no. Poison dart frog tadpoles are harmless. The long answer is a little more interesting, because the natural history of poison dart frogs is a fascinating subject.

Poison dart frogs are a group of frogs in the family Dendrobatidae, native to the rainforests of South and Central America. They get their common name because they are very toxic in their adult form. Although they are small, mainly less than two inches long, they pack a powerful wallop. The golden poison dart frog of the Amazon, Phyllobates terribilis, is so poisonous that native Americans wipe their darts on its back and use the poison to kill monkeys, tapirs, and other large animals (Myers et al 1978). The poison is a neurotoxin so strong that it stops all of the body’s signals, even the involuntary nerve signals that keep the heart beating and breath coming into the lungs. It takes less than 2 micrograms of this poison – an amount smaller than a grain of salt – to kill an adult human, and some frogs can have up to 200 micrograms of poison in their skin (Clarke 1997)! (You may be wondering how people can eat animals that were killed with this poison, since it is so strong. The answer is that the heat of cooking destroys the toxin; Myers et al 1978.) But where does the poison come from? Do the frogs produce it all their lives?

Actually, poison dart frogs get their poison from their diet. As adults, they eat small insects on the forest floor, including ants (Darst et al 2005), millipedes (Saporito et al 2003), and beetles (Dumbacher et al 2004). The insects eat toxic plants and concentrate the poison in their bodies. The frogs can also concentrate the toxins. Special glands on their backs mix the chemicals and secrete a poisonous slime (Angel et al 2003). Poison dart frogs that are kept in captivity and fed non-toxic insects soon lose the ability to produce poison (Preece 1998).

The tadpoles of poison dart frogs are harmless because they don’t eat insects. What do they eat? Unlike frogs in the temperate zone, which lay their eggs in ponds and streams, the female poison dart frog lays her eggs in little pockets of water in the forest, usually caught at the base of plant leaves (Haase and Prohl 2002). Bromeliads and Dieffenbachia are popular frog egg-laying plants (Maura Maple, personal communication). There are no fish in these little pockets of water to prey on the eggs, but there’s also not much in the way of food. Eggs are laid one at a time, because if two tadpoles end up sharing a pool of water, they are likely to eat each other (Caldwell and de Araujo 1998)! After the tadpole hatches, the mother frog returns every day for up to a month (Summers 1999). She sticks her rear end down into the pool of water. If she feels the tadpole wriggling around, she lays an unfertilized egg—the only food for her baby! If she doesn’t feel the tadpole wriggling, she saves the egg for her next offspring, since producing eggs requires a lot of energy. Mother frogs often tend three or four tadpoles at the same time (Beck 1998, Summers 1999).

Poison dart frogs are, without a doubt, one of nature’s great marvels. Because of their toxins, they have very few natural enemies (Darst et al 2005). Compounds from their skin are a potential source of new medicines (Clarke 1997). But they are very vulnerable to the loss of their habitat (Preece 1998). In order to conserve poison dart frogs, we need to keep the rain forest from being destroyed.

--Susan G. Letcher, Ph.D. student, University of Connecticut

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