| Golden Toad | |
|---|---|
| Male golden toad | |
| Conservation status | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Amphibia |
| Order: | Anura |
| Family: | Bufonidae |
| Genus: | Bufo |
| Species: | B. periglenes |
| Binomial name | |
| Bufo periglenes Savage, 1966 |
|
| Synonyms | |
The golden toad (Bufo periglenes) was a small, shiny, bright true toad that was once abundant in a small region of high-altitude cloud-covered tropical forests, about 30 square kilometers in area, above the city of Monteverde, Costa Rica. For this reason, it is sometimes also called the Monteverde golden toad, or the Monte Verde toad. Other common English names include Alajuela toad and orange toad. They were first described in 1966 by the herpetologist Jay Savage.[2] Since May 15, 1989, not a single B. periglenes is reported to have been seen anywhere in the world, and it is classified by the IUCN as an extinct species.[3] Its sudden extinction might have been caused by chytrid fungus and extensive habitat loss.
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The golden toad was one of more than 500 species in the family Bufonidae — the "true toads". B. periglenes inhabited northern Costa Rica’s Monteverde Cloud Forest Preserve, distributed over an area of roughly 10 square kilometres (3.9 sq mi) at an average elevation of 1.5 kilometres (0.93 mi).[4]
Adult males measured just barely 5 centimetres (2.0 in) long. Males have been described as being "Day-Glo golden orange",[5] and unlike most toads their skin was shiny and bright. Jay Savage was so surprised upon first seeing them that he did not believe they could be real; he is quoted as saying: "I must confess that my initial response when I saw them was one of disbelief and suspicion that someone had dipped the examples in enamel paint."[6] Exhibiting sexual dimorphism, female toads were slightly larger than the males, and looked very different. Instead of being bright orange, females were colored dark olive to black with scarlet spots encircled by yellow.
Very little is known about the behavior of B. periglenes;[7] however, it is believed that they lived underground,[7] as they were not seen for most of the year. In contrast, their presence in the Cloud Forest Preserve was obvious during their mating season, which lasted only a few weeks. For a few weeks in April, after the dry season ended and the forest became wetter, males would gather in large numbers near ground puddles and wait for the females. The males would fight with each other for opportunities to mate until the end of their short mating season, after which the toads retreated to their burrows.[7] Eggs were laid in seasonal water catchments in clutches, the average size of which was 228 eggs.[8] After two months, they hatched into tadpoles.[8]
Males outnumbered females, in some years by as much as ten to one, a situation that often led bachelors to attack amplectant pairs and form what Savage once described as "writhing masses of toad balls." The eggs of the golden toad, black and tan spheres, were deposited in small pools--puddles--often no more than one inch deep. Tadpoles emerged in a matter of days, but required another four or five weeks for metamorphosis. During this period, they were highly dependent on the weather; too much rain and they would be washed down the steep hillsides, too little and their puddles would dry up. Golden toads were always found at an altitude of between forty-nine hundred and fifty-six hundred feet. In 1987, an American ecologist and herpetologist, Martha Crump, was fortunate enough to see the toad's mating rituals. In her book, In Search of the Golden Frog [sic], she described it as "one of the most incredible sights I've ever seen," and said they looked like "statues, dazzling jewels on the forest floor."[5] On April 15, 1987, Crump recorded in her field diary that she counted 133 toads mating in one "kitchen sink-sized pool"[5] that she was observing. Five days later, she witnessed the pools in the area drying, which she attributed to the effects of El Niño-Southern Oscillation, "leaving behind desiccated eggs already covered in mold."[5] The toads attempted to mate again that May. Of the 43,500 eggs that Crump found, only twenty-nine tadpoles survived the drying of the forest's ground.[5]
Jay Savage first discovered the toads in 1966.[2] From their discovery in 1966 for about 17 years, and from April to July in 1987, over 1500 adult toads were seen.[4] Only ten[3] or eleven toads were seen in 1988,[4] including one seen by Crump, and none has been seen since May 15, 1989, when Crump last saw the same solitary male toad that she had seen the year before.[7]
In the period between discovery and disappearance, the golden toad was commonly featured on posters promoting the biodiversity of Costa Rica.[9] There is a single anecdotal report from the 1970s of a golden toad in the mountains of Guatemala near the village of Chichicastenango, but this sighting has not been confirmed. There is also another extinct frog sometimes compared to the golden toad found in the same forest in Costa Rica, named Holdridge's Toad.
In the spring of 1987, an American biologist who had come to the cloud forest specifically to study the toads counted fifteen hundred of them in temporary breeding pools. That spring was unusually warm and dry and most of the pools evaporated before the tadpoles in them had time to mature. The following year, only one male was seen at what previously had been the major breeding site. Seven males and two females were seen at a second site a few miles away. The year after, on May 15, 1989, the last sighting of only one male occurred. [10] No golden toad has been seen since then. As late as 1994, five years after the last sighting, researchers still hoped that B. periglenes continued to live in underground burrows, as similar toad species have lifespans of up to twelve years.[4] By 2004 IUCN listed the species as extinct, after an evaluation involving Savage (who had first discovered them 38 years earlier). IUCN's extinction was based on the lack of sightings since 1989 and the "extensive search[ing]" that had been done since without result.[3] In August 2010 a search organised by the Amphibian Specialist Group of the International Union for Conservation of Nature set out to look for various species of frogs thought to be extinct in the wild, including the golden toad.[11]
Jennifer Neville has examined the different hypotheses explaining the extinction of the golden toad in her article "The Case of the Golden Toad: Weather Patterns Lead to Decline". Neville comes to the conclusion that Crump's El Niño hypothesis is "clearly support[ed]" by the available data.[4] IUCN gives numerous possible reasons in its description of the past threats to the species, including "[the golden toad's] restricted range, global warming, chytridiomycosis and airborne pollution".[3] Neville also mentions arguments that an increase in UV-B radiation, fungus or parasites, or lowered pH levels contributed to the Golden Toad's extirpation.[4]
A more recent study confirms the El Niño hypothesis, in which it is stated that "The new study finds that Monteverde was the driest it’s been in a hundred years following the 1986-1987 El Niño, but that those dry conditions were still within the range of normal climate variability". The new study has shown that the Chytrid Fungus has spread due to the dry conditions caused by El Niño. [12]