Strawberry poison-dart frog
The strawberry poison frog or strawberry poison-dart frog (Oophaga pumilio or Dendrobates pumilio) is a species of small amphibian poison dart frog found in Central America. It is common throughout its range, which extends from eastern central Nicaragua through Costa Rica and northwestern Panama. The species is often found in humid lowlands and premontane forest, but large populations are also found in disturbed areas such as plantations. The strawberry poison frog is perhaps most famous for its widespread variation in coloration, comprising approximately 15–30 color morphs, most of which are presumed to be true-breeding. O. pumilio, while not the most poisonous of the dendrobatids, is the most toxic member of its genus.
O. pumilio has a specialized diet of small arthropods, primarily formicine ants and true bugs. The frogs, like most poison dart frogs, are harmless when not fed ants or beetles, resulting in pumilio becoming a rather popular exotic pet.
Oophaga pumilio is diurnal and primarily terrestrial, and can often be found in leaf litter in both forested and disturbed areas. Though brightly colored and toxic, these frogs are relatively small, growing to approximately 17.5–22 mm in standard length. Males are extremely territorial, guarding small territories; females and juveniles are far more sociable.
Male advertisement call
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Reproduction and parental care
Oophaga pumilio is an external breeder, and other species of the genus Oophaga are notable in the amphibian world for exhibiting a high degree of parental care. The strawberry poison frog has dual parental care. The males defend and water the nests, and the females feed the oophagous tadpoles their unfertilized eggs. Although both sexes contribute to parental care, females invest more heavily in terms of energy expenditure, time investment, and loss of potential reproduction. Females provide energetically costly eggs to the tadpoles for 6–8 weeks (until metamorphosis), remain sexually inactive during tadpole rearing, and care for only one clutch of 4–6 tadpoles at a time. The males, on the other hand, contribute the relatively "cheap" (in terms of energy) act of watering and protecting the eggs for a relatively short period (10–12 days), and can care for multiple nests at one time. The extreme maternal investment in their offspring is believed to be the result of high egg mortality. Only 5–12% of the clutch develops into tadpoles, and so the female's fitness may be best increased by making sure that those few eggs that form tadpoles survive.
Unlike many frog species, amplexus is absent in O. pumilio, with mating individuals instead exhibiting a distinct vent-to-vent position in which the female lays eggs and the male fertilizes them. After mating, the female will lay an average of three to five eggs on a leaf or bromeliad axil. The male will then ensure that the eggs are kept hydrated by transporting water in his cloaca. After about ten days, the eggs hatch and the female transports the tadpoles on her back to some water-filled location. In captivity, on rare occasions the male is observed transporting the tadpoles, though whether this is intentional, or the tadpoles simply hitch a ride, is unknown. Bromeliad axils are frequently used tadpole deposition sites, but anything suitable can be used, such as knots in trees, small puddles, or human trash such as aluminum cans.
Tadpoles are deposited singly at each location. Once this has been done, the female will come to each tadpole every few days and deposit several unfertilized food eggs (Savage, 2002). In captivity, tadpoles have been raised on a variety of diets, ranging from algae to the eggs of other dart frogs, but with minimal success. O. pumilio tadpoles are considered obligate egg feeders, as they are unable to accept any other form of nutrition.
After about a month, the tadpole will metamorphose into a small froglet. Generally, they stay near their water source for a few days for protection as they absorb the rest of their tail.
Oophaga pumilio belongs to the genus Oophaga, although the name Dendrobates pumilio is still most commonly used. There is evidence that the species of the Oophaga genus (previously classified as the "female parental care group" of Dendrobates) are a monophyletic evolutionary group. Due to the low level of genetic divergence between the species analyzed in this genus, it is estimated that they speciated relatively recently, after the formation of the current Panamanian land bridge in the Pliocene (3–5 million years ago). Oophaga pumilio is believed to be most closely related to Oophaga arborea.
Oophaga pumilio is a popular frog in captivity, due to its striking colors and unique life cycle. They have been imported in vast quantities to the United States and Europe since the early 1990s, when they would typically be available for around US$30 each. However, these shipments have since stopped, and O. pumilio is much less common and available in reduced diversity. In Europe, O. pumilio is much more diverse and available due to an increased frequency of smuggling and the resulting offspring of smuggled animals. Smuggling of dart frogs is less common elsewhere, but still problematic as it kills large numbers of animals and frequently degrades or destroys viable habitat.
Recently, O. pumilio has been exported from Central America again in small numbers from frog farms. Because of this, pumilio have seen a huge increase in numbers in the dart frog community and is regularly available.
Common color morphs in captivity
One example of a color morph is the blue jeans morph. It is most common throughout the species range, but is relatively rare in the United States pet trade. Most of these animals came from imports during the 1990s, or are their descendents. This morph can be found throughout Costa Rica, as well as mainland Panama.
- Savage, J. M. 2002. The Amphibians and Reptiles of Costa Rica. University of Chicago Press, Chicago and London.
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