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Frogs in Costa Rica

Amphibians/Frogs as Indicators of Environmental Health

Agalychnis callidryas, or Red-eyed Tree Frog
Agalychnis callidryas, 
or Red-eyed Tree Frog

Frogs profoundly enhance our lives and our world in countless ways. They provide vital biomedicines, including compounds that are being refined for analgesics, antibiotics, stimulants for heart attack victims, and treatments for diverse diseases including depression, stroke, seizures, Alzheimer’s, cancer, and even AIDS.

Smilisca phaeota, Masked Tree Frog
Smilisca phaeota, Masked Tree Frog

The thin skin of frogs help them drink and breathe, but also make them susceptible to environmental contaminants, particularly agricultural, industrial, and pharmaceutical chemicals. These sensitive frogs have been likened to canaries in the coal mine: just as miners used sensitive canaries to warn them of toxic gases in the mines, so the condition of frogs on Earth might be warning us of unsafe environmental conditions that could eventually seriously impact our health.


Red-eyed Tree Frog Mating (male on top)
Red-eyed Tree Frog Mating (male on top)
Red-eyed Tree Frog eggs
Red-eyed Tree Frog eggs

Could we be similarly affected by these widespread endocrine disruptors, or are we already? Some human studies suggest that the average sperm count of adult men in certain populations is significantly decreased, as much as 50% of what it was two generations ago. Are we also suffering the same feminizing effects of agrochemicals, industrial waste, and other estrogen-mimics that we see affecting amphibians so drastically?

Frog Habitat
Butterfly Conservatory – Frog Habitat

So frogs are vital components of their ecosystems. In areas of the world where they have declined, there has been an increase in invertebrate pests that damage crops and that carry human diseases. Frogs have also played a vital role in human culture. While in some cultures frogs and toads have been despised and regarded as evil, other cultures have embraced them as life-giving keepers of the rains or agents of fertility and good luck.


Dendrobates pumilio, Blue-Jean or Strawberry dart frog
Dendrobates pumilio,
Blue-Jean or Strawberry dart frog

Poison Dart Frogs Poison dart frogs belong to the Dendrobatidae family. Their skin glands produce one of the strongest toxins in the animal world: batrachotoxin, from the ancient Greek word batrachos–frogs and toxin–poison). These unique frogs are very small in size (reaching only 2-5 cm in length).

There are 12 species in the genus Dendrobates. They are all brightly colored: dendrobates auratus, is green with black markings. Dendrobates pumilio is the smallest member of the family. It is bright red with tiny dark spots, and the legs are either blue or black. They are called the blue jeans (or black jeans) frog.

Where They Live

Poison Dart Frogs have elaborate courtship rituals and most all display an impressive level of parental care. The habitat of dart-frogs is in the understudy of tropical forests where it’s warm and the humidity level is very high. They move both on the ground and on plants, they can also climb trees easily by virtue of adhering disks at the end of the fingers.

Behavior and Reproduction

Dendrobates auratus, Green & Black dart frog
Dendrobates auratus,
Green & Black dart frog

Male frogs go through an elaborate ritual to attract mates, including fighting among themselves to establish territories. The male then attracts a female with calls using trilling sounds, and then by rubbing against her as part of his ritual.After the eggs are laid the male takes responsibility for them, and once the tadpoles hatch they climb onto his back and he carries them to water pooled in jungle plants for further development. The adult frogs return to check on the tadpoles occasionally during the 6-8 week period it takes to develop into adult frogs.

How they make the Poison

Poison dart frogs have a diet of alkaloid rich insects like ants, termites, centipedes, and spiders. The poison is synthesized from a complex group of toxins derived from these insects and then collected in glands in the frog’s skin. When this poison enters the body of a victim, it affects the nervous system and quickly causes the heart to stop beating.


Dendrobates pumilio
Dendrobates pumilio

How the Indians used the Poison The Indians of South America used a blowgun made from a hollow stem, with small darts made from large thorns. They kept the poison frogs in captivity until they were ready to go hunting, and then they rubbed the tip of the on the back of the frog, and blew them at their prey. Only one drop of this poison will kill a bird or small animal, and the poison from just one frog is enough to kill a human if ingested.

Medicinal Uses for the Poison

Scientific research on the poison of dart frogs is being done to determine possible medicinal uses. According to the National Institute of Health, poison dart frogs offer over 300 alkaloid components–chemicals that are similar to cocaine and morphine. Some medicines have already been produced and are being used as anesthetics in surgery.

Dendrobates pumilio – Blue-jeans/Strawberry Poison Dart Frog

Dendrobates pumilio
Dendrobates pumilio


This species is present from Nicaragua to Panamá. Is a diurnal species, inhabit semi-open areas in the understory. This species use the bromeliads as private water tanks for their tadpoles wich are given born in the understory and then transported; one at the time, by the mother (Sometimes also the father) to their private pool in a bromeliad.

Dendrobates auratus – Green and Black Poison Dart Frog


Dendrobates auratus
Dendrobates auratus

They are black and green or light blue in color, very variable, but usually the black in spots or broken bands. They have no teeth on the upper jaw. Second and third fingers are thick compared to other types of frogs (about twice the normal size) and thicker in the males than in females. Finger and toe tips have a glandular muscular adhesive pad. Webbing and lateral skin folds are absent. There are distributed from Costa Rica to Colombia.The most widely known fact about these frogs seems to be that Amerindians use the skin secretion, which contains a powerful nerve toxin to tip their blowguns darts. This substance creates irreversible blocking of motor neurons if a sufficient amount enters the blood stream. Death results through muscular and respiratory paralysis.