Golden poison frog
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Myers, Daly, and Malkin, 1978
The golden poison frog (Phyllobates terribilis), also known as the golden frog, golden poison arrow frog, or golden dart frog, is a poison dart frog endemic to the Pacific coast of Colombia. The optimal habitat of P. terribilis is the rainforest with high rain rates (5 m or more per year), altitudes between 100 and 200 m, temperatures of at least 26°C, and relative humidity of 80–90%. In the wild, P. terribilis is a social animal, living in groups of up to six individuals; however, captive P. terribilis specimens can live in much larger groups. These frogs are often considered innocuous due to their small size and bright colours, but wild frogs are lethally toxic, and may be the most poisonous of any living animal.
Distribution and habitat
The golden poison frog is endemic to humid forests of the Pacific coast of Colombia in the Cauca and Valle del Cauca Departments. It is only known from primary forest. The eggs are laid on the ground; the males transport the tadpoles to permanent pools.
The golden poison frog's skin is densely coated in an alkaloid toxin, one of a number of poisons common to dart frogs (batrachotoxins), which prevents nerves from transmitting impulses, leaving the muscles in an inactive state of contraction. This can lead to heart failure or fibrillation. Some native people use this poison to hunt by coating darts with the frog's poison. Alkaloid batrachotoxins can be stored by frogs for years after the frog is deprived of a food-based source, and such toxins do not readily deteriorate, even when transferred to another surface.
The golden poison frog is not venomous, but poisonous: venomous animals have a delivery method for the toxin, such as fangs or spines, while poisonous animals and plants do not have a delivery method and rely on transference of the toxin, typically but not limited to ingestion. Like most poison dart frogs, P. terribilis uses poison only as a self-defense mechanism and not for killing prey. The most venomous animal, in terms of LD50, is the inland taipan, although its venom is less potent than the defensive toxins in P. terribilis.
The average dose carried will vary between locations, and consequent local diet, but the average wild P. terribilis is generally estimated to contain about one milligram of poison, enough to kill about 10,000 mice. This estimate will vary in turn, but most agree this dose is enough to kill between 10 and 20 humans, which correlates to up to two African bull elephants. This is roughly 15,000 humans per gram.
This extraordinarily lethal poison is very rare. Batrachotoxin is only found in three poisonous frogs from Colombia (genus Phyllobates) and three poisonous birds from Papua New Guinea: Pitohui dichrous, Pitohui kirhocephalus, and Ifrita kowaldi. Other related toxins, histrionicotoxin and pumiliotoxin, are found in frog species from the genus Dendrobates.
The golden poison frog, like most other poisonous frogs, stores its poison in skin glands. Due to their poison, the frogs taste vile to predators; P. terribilis poison kills whatever eats it, except for one snake species, Liophis epinephelus. This snake is resistant to the frog's poison, but is not completely immune.
The poisonous frogs themselves are perhaps the only creatures to be immune to this poison. Batrachotoxin attacks the sodium channels of the cells, but the frog has special sodium channels the poison cannot harm.
Since easily purchased foods are not rich in the alkaloids required to produce batrachotoxins, captive frogs do not produce toxins and they eventually lose their toxicity in captivity. In fact, many hobbyists and herpetologists have reported that most dart frogs will not consume ants at all in captivity, though ants constitute the larger portion of their diets in the wild, likely due to the unavailability of the natural prey species of ants to captive frog keepers. Though all poison frogs lose their toxicity when deprived of certain foods, and captive-bred golden poison frogs are born harmless, a wild-caught poison frog can retain alkaloids for years. It is not clear which prey species supplies the potent alkaloid that gives golden poison frogs their exceptionally high levels of toxicity, or whether the frogs modify another available toxin to produce a more efficient variant, as do some of the frogs from the genus Dendrobates.
Thus, the high toxicity of P. terribilis appears to be due to the consumption of small insects or other arthropods, and one of these may truly be the most poisonous creature on Earth. Scientists have suggested the crucial insect may be a small beetle from the family Melyridae. At least one species of these beetles produces the same toxin found in P. terribilis. Their relatives in Colombian rainforests could be the source of the batrachotoxins found in the highly toxic Phyllobates frogs of that region.
P. terribilis is the largest species of poison dart frog, and can reach a size of 55 mm as adults, with females typically being larger than males. Like all poison dart frogs, the adults are brightly coloured, but they lack the dark spots present in many other dendrobatids. The frog's colour pattern is aposematic (which is a warning pigmentation to warn predators of its toxicity). The frog has tiny adhesive disks on its toes, which aid climbing of plants. It also has a bone plate in the lower jaw, which gives it the appearance of having teeth, a distinctive feature not observed in the other species of Phyllobates. The frog is normally diurnal. P. terribilis occurs in three different colour varieties or morphs:
The largest morph of P. terribilis exists in the La Brea area of Colombia, and is the most common form seen in captivity. The name "mint green" is actually rather misleading, as the frogs of this morph can be metallic green, pale green, or white.
The yellow morph is the reason it has the common name golden poison dart frog. Yellow P. terribilis specimens are found in Quebrada Guangui, Colombia. These frogs can be pale yellow to deep, golden yellow in colour. A frog sold under the name "gold terribilis" was once believed to be a deeper yellow P. terribilis. However, genetic tests have proven these frogs to be uniform-coloured morphs of Phyllobates bicolor.
While not as common as the other two morphs, orange examples of P. terribilis exist in Colombia, as well. They tend to be a metallic orange or yellow-orange in colour, with varying intensity.
The main natural sources of food of P. terribilis are the ants in the genera Brachymyrmex and Paratrechina, but many kinds of insects and other small invertebrates can be eaten, specifically termites and beetles, which can easily be found on the rainforest floor. This frog is considered the most voracious of the dendrobatids.
In captivity, the frog is fed with Drosophila fruit flies, cochineals, crickets (Gryllidae), the larvae of various insects, and other small, live, invertebrate foods. An adult frog can eat food items much larger in relation to its size than most other dendrobatids. Tadpoles feed on algae, mosquito larvae, and other edible material that may be present in their nursery. Unlike other Phyllobates spp., P. terribilis tadpoles are somewhat versatile feeders.
Poison frog and the indigenous peoples
P. terribilis is a very important frog to the local indigenous cultures, such as the Choco Emberá people in Colombia's rainforest. The frog is the main source of the poison in the darts used by the natives to hunt their food.
The Emberá people carefully expose the frog to the heat of a fire, and the frog exudes small amounts of poisonous fluid. The tips of arrows and darts are soaked in the fluid, and keep their deadly effect for over two years.
P. terribilis is considered to be one of the most intelligent anurans. Like all poison dart frogs, captives can recognize human caregivers after exposure of a few weeks. They are also extremely successful tongue hunters, using their long, adhesive tongues to catch food, and almost never miss a strike. This success at tongue-hunting implies better brainpower and resolution of eyesight than some other frogs.
Golden poison frogs are social animals. Wild specimens typically live in groups of four to seven (average six); captive frogs can be kept in groups of 10 or even 15, although groups that rise past that number are extremely susceptible to aggression and disease. Like all poison dart frogs, they are rarely aggressive towards members of their own species; however, occasional minor squabbles may occur between members of the group. Being immune to their own poison, golden poison frogs interact constantly with each other. They communicate not only with their calls, but also with gestures. Push-up movements are a sign of dominance, while lowered heads seem to signal submission.
Like all members of the genera Phyllobates, Dendrobates, and Ranitomeya, family groups of golden poison dart frogs assemble into large breeding gatherings once or twice per year. While peaceful towards others of their species at other times, the male frogs can be formidably aggressive while competing for a breeding space. Females will remain fairly calm throughout this ordeal. Courtship for the golden poison frog is similar to that of the green and black poison dart frog. Its call consists of a rapid series of high-pitched squeaks. Golden poison frogs are notable for demonstrating tactile courtship during reproduction, each partner stroking its mate's head, back, flanks, and cloacal areas prior to egg deposition. The eggs are fertilized externally.
P. terribilis frogs are dedicated parents. The golden poison frogs lay their eggs on the ground, hidden beneath leaf litter. Once the tadpoles emerge from their eggs, they stick themselves to the mucus on the backs of their parents. The adult frogs carry their young into the canopy, depositing them in the pools of water that accumulate in the centre of bromeliads and water-filled tree holes. The tadpoles feed on algae and mosquito larvae in their nursery. After metamorphosis is complete, parent frogs lead the froglets to an existing group.
Like the other poison dart frogs, P. terribilis is harmless when raised away from its natural food source. They are a popular rainforest vivarium subject, and are somewhat easier to feed than some other dart frogs. Larger species of fruit flies, small crickets, waxworms, small mealworms, termites, and phoenix worms can be used if supplemented with calcium and other minerals. The temperature should be in the low to mid 20s (°C). They are sensitive to high heat and suffer from a condition called "wasting syndrome" if overheated for too long. They require high humidity, as they come from one of the world's most humid rainforests. The Cali Zoo has a captive population of over 50 individuals. They are fed with crickets and share a habitat with several species of Colombian tree frogs.
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