Strawberry Poison-Dart Frog

Poison on loan

Most amphibians make their own defensive chemicals. Poison frogs collect theirs from what they eat. The strawberry poison-dart frog, Oophaga pumilio, is one of them. The chemicals are called alkaloids, and they sit in glands in the frog’s skin.

So where do they come from? Oribatid mites collected in Costa Rica and Panama held about 80 alkaloids, and 41 of them also occur in this frog. Ants are a source too. Formicine ants of two genera carry pumiliotoxins, which are major alkaloids in this frog, and those ants turned up in the stomach contents of the frogs. The frog eats mostly ants, and mites make up a significant part of its diet.

Poisoned baby food After the eggs hatch, a mother carries each tadpole to a watery hollow in the plants. She then returns for about six weeks to feed it unfertilized eggs. Those eggs hold traces of alkaloids, and the researchers suggest this frog may be the first animal known to actively provision its offspring after hatching with chemical defenses.

Tiny, bright and picky about color

Adults are 17 to 24 mm long and weigh about 2 grams. The typical frog is bright red with blue legs, but the back can also be blue, yellow, white, green, black or orange. The bright colors work as a warning to predators.

The species has more than 15 distinct color morphs, mostly separated by geography. Most of them live on the islands and nearby mainland of the Bocas del Toro Archipelago in Panama.

Color matters to the frogs too. In tests across several populations, the results pointed to a male’s back color as the most important factor in what females preferred.

Wrestling on the forest floor

Males call to mark a territory. If another male answers and approaches, they often wrestle, and a match can last up to 20 minutes. At La Selva Biological Station, studies found males defending territories of 0.24 to 4.78 square metres. These frogs are active by day and usually stay close to the forest floor. They are mostly solitary, and gather to breed.

Where it lives

The frog is found in lowland forests along the Caribbean side of Central America, from Nicaragua to Panama. It typically lives in rainforest and also in cacao groves. The IUCN Red List rates it Least Concern.