Blue Jeans Poison Dart Frogs
Last Updated: Jun 17, 2015
The tiny blue jeans poison dart frog, also known as the strawberry poison arrow frog, is one of Costa Rica’s most colorful and iconic amphibians. Its distinctive “chirp-chirp-chirp” is a forest favorite, easily heard and mimicked by naturalist guides and their attentive travelers.
As adults, blue jeans dart frogs measure between 0.75 and one inch long. The species is comprised of an estimated 15-30 color morphs – the most common in Costa Rica are reddish-orange with black spots (colloquially called strawberry dart frogs) and bright red with distinct, blue markings on their toes and legs, referred to as blue jeans poison dart frogs. Other morphs include the green jeans frog, which is red with green coloration on the legs and lower body.
The blue jeans dart frog is one of the world’s most studied and photographed amphibians, due in large part to its diurnal habits, large population, charming colors, and reproductive biology. In fact, the frog’s genus was changed in 2006 from Dendrobates to Oophaga after a study discovered unique parenting patterns, including the fact that the tadpoles’ diet consisted purely of unfertilized eggs from their mother. (Obligatory oophagy means the young can only feed on eggs of the same species.)
Strawberry dart frogs are generally seen on the forest floor, where they move with jerky movements, small hops, and exaggerated walking motions to navigate organic matter and approach their prey. The species is poisonous, but only when orally ingested or when its skin oils are rubbed on an open wound. Poison dart frogs, also known as poison arrow frogs, get their nickname from the ancient indigenous practice of rubbing frog toxins on arrows and blow-darts to incapacitate prey.
Blue jeans poison dart frogs are native to most of Central America and are common in Costa Rica’s Central Valley and Caribbean slope, mostly in lowland rainforest. For good chances at spotting this colorful frog, head to Puerto Viejo, Puerto Viejo de Sarapiqui, or Tortuguero. The amphibian is usually found on the forest floor, hunting for the ants and mites that make up 90% of its diet. Males are very territorial, generally calling to their mates from low-lying branches and fallen logs no more than three feet above the ground.
Both male and female strawberry dart frogs stay within their home areas of approximately 21 to 175 square feet and many frogs may live within the same home range. Male territories measure from 2.5 to 51.5 square feet; territories do not overlap. Males permit females and non-calling males to enter their territory, but will defend it from other mating males. When an intruder invades, the resident male calls to it. If the intruder does not leave, he will call back and the resident male will initiate a fight that may last up to 20 minutes. Males stand on their hind legs to wrestle, holding each other chest-to-chest. The loser is released and must retreat from the territory.
Mating occurs year-round and is initiated when an interested female approaches a calling, or singing, male. The male leads the female to a safe breeding area, usually under leaves. The frogs will face away from each other during mating, which generally lasts from 10 minutes to three hours. Clutch sizes range from three to five eggs per, and females can lay up to one clutch per week.
After fertilization and egg laying, the male will return daily to moisten the eggs. After an incubation period averaging seven days, the eggs hatch into tadpoles and the mother carries each tadpole to a separate bromeliad plant. The mother will always return to take care of her offspring – she delivers unfertilized eggs, their only nutrition, to each tadpole once a day, usually in the morning. In general and unlike in most other frog species, mothers will feed only their offspring, even when other tadpoles solicit her for unfertilized eggs (this is called “begging behavior”).
Tadpoles metamorphose into froglets within 43-52 days. The froglets, which measure approximately 0.4 inches and are a deep maroon color, continue to grow over the next ten months until they reach sexual maturity.
Status in the Wild:
The blue jeans dart frog is not endangered, despite its popularity in the international pet trade. The frog’s bright colors are a warning to potential predators that cannot digest their alkaloid-based toxins. Because of this, the amphibians have few predators, though birds have been observed attacking even the brightest colored specimens.
Like all amphibians, blue jeans poison dart frogs are commonly thought to suffer from environmental effects much earlier than other species. They are therefore considered an indicator species that alerts humans to environmental changes worldwide.