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Dendrobates auratusGreen and Black Dart-poison Frog

By Rachel Schafer

Geographic Range

Dendrobates auratus can be found in Central and South America, from Nicaragua and Costa Rica to southeastern Brazil and Bolivia. They were also introduced in Hawaii by humans, and have flourished there. ( http://ecology.miningco.com/library/weekly/aa012598.htm)

Habitat

Dendrobates auratus adults are found on the floor of rain forests. They prefer locations near small streams or pools. The tadpoles live in these small pools or streams. Where the frogs live in the heavily populated areas of Hawaii, the eggs are often deposited in broken beer bottles or old cans instead of the usual puddle. (Whitfield 1984)

  • Aquatic Biomes
  • rivers and streams
  • temporary pools

Physical Description

Dendrobates auratus has many color variants. Most of them are black and either green or light blue, with the black in bands or spots. The Hawaiian frogs are metallic green or brownish-black. The adults are approximately 4 cm long. As is true of most frogs, adults have a fused head and trunk with no tail. Tadpoles use gills to breathe, unlike the adults, which breathe through lungs. Tadpoles also lack legs and have tails, which is appropriate for their watery habitat. Another important physical characteristic of D. auratus is the poison glands located throughout the surface of their body. Their bright colors are believed to encourage predators with color vision to avoid the frogs. The boldly contrasting patterns may be aposematic to predators that lack color vision, although this has not been proven. Approximately 90 alkaloids have been identified from all species of dendrobatids <<Dendrobatidae>.. (Myers & Daly, 1976)

  • Sexual Dimorphism
  • sexes alike
  • Average length
    4 cm
    1.57 in

Development

Reproduction

Male frogs go through an elaborate ritual to attract mates. The male first fight among themselves to establish territories, which are then fixed for the remainder of the mating season. The male then attracts a female with vocalizations consisting of trilling sounds. Part of mating behavior involves the frogs rubbing against each other.

Once the courtship ritual is completed, the female lays up to six eggs in a small pool of water. The eggs are encased in a gelatinous substance for protection. The mating season of D. auratus occurs throughout the entire rainy season of the rain forest, from mid-July through mid-September.

  • Breeding interval
    Breeding may occur more than once yearly.
  • Breeding season
    Reproduction occurs during the rainy season, July to September.
  • Range number of offspring
    6 (high)
  • Average time to independence
    8 weeks

During the two week development period, the male returns to the eggs periodically to check on them. Once the tadpoles hatch, they climb onto the males back and he carries them to a place suitable for further development, such as a lake or a stream. For the duration of this trip, the tadpoles are attached to the males back by a mucus secretion, which is soluble only in water so that there is no chance of them accidentally falling off. Once they are at their final destination, the tadpoles are on their own. They take an additional six weeks to develop into adult frogs. (Mattison 1987)

Lifespan/Longevity

Longevity is not well-known.

Behavior

Dendrobates auratus are diurnal, and are seldom still during the day, constantly searching for food and taking care of young with distinctive hopping motions. Although the color pattern of these frogs is used to warn predators of their poison and not to attract mates, the mating ritual is quite elaborate. The male frogs with fight each other, and when the females have chosen their mate, the males stay in their own territories. (Mattison 1987)

Communication and Perception

Little is known of communication in this species. Males use vocalizations to attract females for mating and advertise territories. It is also possible that visual displays, tactile stimuli, and chemical cues are involved. They use their excellent vision to capture prey.

Food Habits

Dendrobates auratus individuals prey on small invertebrates. Most notably, these frogs eat ants that have high quantities of alkaloids in their tissues. The frogs can sequester those alkaloids in their skin, which is what makes them poisonous. Dendrobates auratus individuals kept in captivity and fed a diet of insects without alkaloids will lose their toxicity. These frogs capture their prey by using their sticky, retractible tongues as well as their excellent eyesight. (Obst 1988)

  • Animal Foods
  • insects
  • terrestrial non-insect arthropods

Predation

Dendrobates auratus avoids predation through their aposematic coloration and extremely toxic skin secretions.

Ecosystem Roles

Poison dart frogs are important predators of small invertebrates.

Economic Importance for Humans: Positive

Dendrobates auratus have long been used by local peoples to provide poison for their weapons. Currently the possibility of various medicines being derived from the frogs is being explored. Pharmaceutical companies are investigating the possibilities of a painkiller, ABT-594, being developd from a compound called epibatidine, which is found in D. auratus. The drug has the potential to be approximately 200 times more potent than morphine in blocking pain in animals, yet shows no sign of side effects of addiction. Since there have been over 80 alkaloids discovered from the 20 species of dendrobatids, there is much more research being conducted, especially on the effects of the alkaloids on neurological and muscular disorders. These frogs are also bred in captivity and sold extensively in the exotic pet trade. People enjoy them as pets because they are so colorful, and although they provide a challenge to owners, they do fairly well in captivity. (Merickel 1998)

Economic Importance for Humans: Negative

There are no negative impacts of these frogs on humans, although the skin of these frogs is highly toxic and unprotected contact can be dangerous.

Conservation Status

Dendrobates auratus are not currently listed as in danger. However, with the destruction of their habitat, tropical rain forests, it is now likely that in a short time they will be in trouble. In fact, it is speculated that members of the genus Dendrobates will be the first poison dart frogs to be put on the endanged list of a major conservation organization such as CITES or ESA.

( http://ecology.miningco.com/library/weekly/aa012598.htm)

Other Comments

Poison dart frogs appear to be highly adaptabe, since they do well in aquariums, and they were successfully introduced in Hawaii. They make excellent pets for decoration, although they can't be touched because of their toxicity. They are colorful and lively, as well as being relatively easy to maintain. They do, however, tend to lose their toxicity when kept in captivity, possibly because of the loss of wild food sources. With the rain forests disappearing every day, the danger to the frogs is evident. Although scientists are studying their toxins and the possibility of obtaining medicines from D. auratus, the time is fast approaching when it may not be possible to take advantage of all the frogs have to offer us. (Hundt 1997)

Contributors

Rachel Schafer (author), University of Michigan-Ann Arbor.

Glossary

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

acoustic

uses sound to communicate

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

aposematic

having coloration that serves a protective function for the animal, usually used to refer to animals with colors that warn predators of their toxicity. For example: animals with bright red or yellow coloration are often toxic or distasteful.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

diurnal
  1. active during the day, 2. lasting for one day.
drug

a substance used for the diagnosis, cure, mitigation, treatment, or prevention of disease

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

external fertilization

fertilization takes place outside the female's body

fertilization

union of egg and spermatozoan

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

insectivore

An animal that eats mainly insects or spiders.

introduced

referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

male parental care

parental care is carried out by males

metamorphosis

A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

oceanic islands

islands that are not part of continental shelf areas, they are not, and have never been, connected to a continental land mass, most typically these are volcanic islands.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

pet trade

the business of buying and selling animals for people to keep in their homes as pets.

poisonous

an animal which has a substance capable of killing, injuring, or impairing other animals through its chemical action (for example, the skin of poison dart frogs).

polygynous

having more than one female as a mate at one time

polymorphic

"many forms." A species is polymorphic if its individuals can be divided into two or more easily recognized groups, based on structure, color, or other similar characteristics. The term only applies when the distinct groups can be found in the same area; graded or clinal variation throughout the range of a species (e.g. a north-to-south decrease in size) is not polymorphism. Polymorphic characteristics may be inherited because the differences have a genetic basis, or they may be the result of environmental influences. We do not consider sexual differences (i.e. sexual dimorphism), seasonal changes (e.g. change in fur color), or age-related changes to be polymorphic. Polymorphism in a local population can be an adaptation to prevent density-dependent predation, where predators preferentially prey on the most common morph.

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

tactile

uses touch to communicate

terrestrial

Living on the ground.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

vibrations

movements of a hard surface that are produced by animals as signals to others

visual

uses sight to communicate

References

Hundt, Anthony. 1997. http://206.1.0.131/Dendrobatidae/Dendrobates/Dauratus.html.

Mattison, Chris. 1987. Frogs & Toads of the World. Facts of File Publications, New York.

Merickel, Jim. 1998. http://ecology.miningco.com/library/weekly/aa012598.htm.

Myers, C.W. and J. W. Daly. 1976. Preliminary Evaluation of Skin Toxins and Vocalizations in Taxonomic and Evolutionary Studies of Poison-

Obst, Fritz Jurgen. 1988. Atlas of Reptiles and Amphibians. TFH Publications, Neptune City.

Whitfield, Philip ed. 1984. Macmillan Illustrated Animal Encyclopedia. Macmillan Publishing Co., Inc. New York.

LINKS TO IMAGES: --http://www.oit.itd.umich.edu:80/bioweb/display/herp/047.herp.JPG --http://www.lam.mus.ca.us/nhm/departments/research/herpetology/herpimages/fgreen.htm --http://www.lam.mus.ca.us/nhm/departments/research/herpetology/herpimages/fgreen.htm

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