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.

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Brazil

View distribution map in BerkeleyMapper.

Dendrobates castaneoticus occurs in the primary lowland forest near Cachoeira Juruá, Rio Xingu and the Tapajos drainage, State of Pará, Brazil. Though rarely collected, the distance between these two major collection sites suggests a rather broad distribution. Active only by day, they forage mainly in the leaf-litter at ground level and are rarely found far above the ground.

Life History, Abundance, Activity, and Special Behaviors
Dendrobates castaneoticus is an insectivore and feeds primarily on ants, termites and other small insects. Although clutches containing up to 12 eggs have been reported, the female usually lays 2-6 eggs, which are cared for by the male. When the tadpoles hatch they are deposited individually in small pools of water, which has collected in logs, tree holes, Brazil nut husks, or other debris. The tadpoles are large and aggressive and will devour any insect larvae, tadpoles, or plant matter of appropriate size. Young frogs grow quickly and may reach maturity as early as 5-7 months.

Trends and Threats
This frog is not listed as endangered, but little data exists to verify the size of the wild population. Overexploitation for pet trade, habitat destruction resulting from deforestation and agriculture may ultimately leady to a reduction in populations and/or individual numbers.

Relation to Humans
This species has begun to show up more commonly in captive collections, and is gaining popularity in the pet trade, with captive bred specimens selling for over 100 dollars (U.S.).

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Intensified agriculture or grazing
Habitat fragmentation
Intentional mortality (over-harvesting, pet trade or collecting)

Comments
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.

References

Caldwell, J. P. and Myers, C. W. (1990). ''A new poison frog from Amazonian Brazil: with further revision of the quinquevittatus group of Dendrobates.'' American Museum Novitates, 2988, 1-21.

Species Account Citation: AmphibiaWeb 2010 Adelphobates castaneoticus: Brazil-nut Poison Frog <https://amphibiaweb.org/species/1629> University of California, Berkeley, CA, USA. Accessed Dec 27, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 27 Dec 2024.

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