Description

Dendrobates castaneoticus, or the Brazil-nut Poison Frog, is among the smallest of the poison dart frogs, with a snout-vent length (SVL) ranging from 18-23 mm. This species varies little in color, size, and pattern across its range in northeastern South America. The body color is a glossy black with white to yellow spots or tick marks on the dorsal surface, which may appear as partial lines in some individuals. The area of insertion of the forelimbs to the body and the hind limbs above and below the knee joint are marked with bright orange or yellow spots. These spots may serve to distract or confuse predators when the frog is in motion. When at rest, the spots on the hind limb appear to be a single large spot. One additional spot appears on the under side of the calf, but is only visible from a ventral view. This species completely lacks an inner metacarpal tubercle. Adult females are usually larger than males, and only the males are capable of calling.

The common name "Brazil-nut Poison Frog" comes from this frog’s proclivity for depositing its tadpoles in the fruit capsules of brazil nut trees. This behavior is part of a complex and interesting system involving many species. The brazil-nut fruit falls from the tree and the outer husk is chewed open by a large mammal such as an agouti. The agouti removes the edible insides of the fruit capsule leaving it hollow. The capsule then fills with rainwater and becomes prime breeding ground for many different tiny creatures such as dart frogs, toads, mosquitoes, and other insects. Each of these larvae are potential predators of one another, and survival depends on their ability to compete as well as the timing of their deposition.