MONTEVERDE GOLDEN TOAD
The Monteverde golden toad is more glamorous and mysterious than it seems an amphibian could be. Its glamour is nature-made but its mysterious decline probably is due to humans.
Golden toads have never been widespread, but they used to be abundant in a handful of areas of cloud-shrouded tropical forest above the Costa Rican town of Monteverde. No one has seen a golden toad since 1989.
Species Description and Range
The Monteverde golden toad was first described in the 1960s in a scientific paper entitled “An Extraordinary New Toad from Costa Rica.” Extraordinary, it is! The males, just barely two inches (5 cm) long, are an unbelievably bright orange. Unlike most toads, their skin is shiny and brilliant.
A renowned herpetologist was so surprised upon first seeing them that he said it appeared as if they had been “dipped in enamel paint.” The females look different, but just as spectacular. Slightly larger than the males, females are dark olive to black with spots of scarlet encircled by yellow.
Very little is known about golden toad behavior. In the Monteverde forest, golden toads were conspicuous only during the breeding season. For a few weeks each April, the males gathered in groups of hundreds in small pools of water to wait for females.
Breeding activity lasted a week or two, then the toads would disappear for another year. The eggs were laid in seasonal water catchments, where the tadpoles would hatch and grow into adults in a very short time.
In 1987, the golden toad was closely studied by an American ecologist and herpetologist who, by chance, happened upon its breeding spectacle. She described it as brief and breathtaking; the males looked like “little jewels on the forest floor.” She was so fascinated that she applied for a grant to return and study the toads.
In 1988, no toads appeared when the seasonal rains started. During several months of searching the Monteverde forest, scientists found only ten Monteverde golden toads, and none were breeding. In 1989, only one lonely toad was found where once there were hundreds. Despite much searching, not a single golden toad has been seen since then.
The Monteverde golden toad is an amphibian, the group of animals that includes frogs, toads, and salamanders. Among the oldest creatures on earth, amphibians first appeared some 350 million years ago. They are characterized by a complex biology, which includes life both in the water and on land.
Most amphibians begin life as eggs, laid in or near water, and hatch into free-swimming young, then they grow into air-breathing adults (see metamorphosis). Amphibians have lungs for breathing, but they also have the ability to absorb oxygen through their skin.
Distributed worldwide, amphibians are adapted to a variety of habitats and lifestyles. Some climb trees, some burrow underground, and others live an entirely aquatic life. They can be found from tropical forests, to wetlands, to mountain tops, to deserts. They range in size from giant ten-pound (4.5 kg) toads to the tiniest of tree frogs.
Wherever they occur, amphibians play a key role in the natural ecosystem. They are important both as predators, eating huge numbers of insects and other small creatures, and as prey for larger animals, including fish, birds, mammals, and reptiles.
Like reptiles, amphibians are cold-blooded, which means their body temperature is about the same as the temperature in the surrounding environment. Amphibians bask in the sun to keep warm, and some burrow or hibernate to escape very cold, hot, or dry weather.
Frogs and toads have been featured in the folklore and mythology of many cultures. Ancient Aztecs believed that toads were guardians of the underworld. Chinese and Indian mythology describes a three-legged frog that holds up the world and causes earthquakes when it moves. Frogs and toads are popular characters in literature and are often depicted as wise or clever creatures.
Humans have long used frogs as food. We are only beginning to understand the potential medicinal uses of amphibians. For example, not all poison-dart frogs are toxic; one brilliantly-colored frog secretes a chemical that may be useful as a cardiac stimulant for heart-attack patients, and another produces a powerful painkiller which may some day be an alternative to morphine.
Causes of Endangerment
Amphibians in general are particularly sensitive to changes in their habitat and in climate because they live both on land and in water, they are both predators and prey, and they have permeable skin. Many factors appear to be interacting to cause their decline.
Habitat destruction and alteration has taken its toll on amphibians. Worldwide, ponds, rivers, and marshes have been drained, diverted, and polluted; recreational lakes are stocked with non-native fish or frogs that out-compete or prey on native species; forests are logged or converted to cropland or pasture; and human development obliterates other amphibian habitats.
In Guatemala, home to 120 amphibian species, 50 to 75 percent of the rainforest has been clearcut or burned in the last 15 years. Those animals not killed outright are left with no natural habitat.
Habitat destruction does not explain the disappearance of the Monteverde golden toad, however. The high-elevation rain forest where it lived is a relatively pristine area, protected as a national reserve since the 1970s.
The unexplained, sudden disappearance of the Monteverde golden toad is not a unique story. Populations of frogs, toads, and salamanders are declining or disappearing the world over. In the late 1980s the scientific community first took notice of this alarming trend, which continues today.
Recent examples of this phenomenon include the reported decline of whole communities of frogs in areas as different and far apart as a National Park in the western United States and the montane rain forest of eastern Australia.
In the Australian rain forest, at least 14 species of stream-dwelling frogs have disappeared or declined sharply (by more than 90%) during the past fifteen years, according to a report published in April 1996.
These precipitous declines are widespread across a large area of rain forest, suggesting that habitat destruction by itself is not a likely cause.
In Yosemite National Park in the United States, scientists recently discovered the large-scale collapse of an entire community of amphibians. Surveys conducted in 1992 revealed that all seven native species of frogs and toads in the region of Yosemite have declined since 1915.
Three species have disappeared entirely from this nearly pristine National Park. Researchers found only one western toad, which was once described as being “exceedingly abundant.” The only species that was reported to be more widespread is the one non-native species, the bullfrog, which was introduced to the area in the late 1800s.
Amphibians are now the object of intensive studies to solve the mystery of their decline. Where habitat destruction is not the obvious cause, it is thought that other, less-visible problems, such as pollution, acid rain, drought, disease, human exploitation, and ozone depletion may be killing the animals.
Amphibians are part of the diet of many local peoples around the world. A low level of subsistence hunting rarely decimates a population. The recent rise in commercial utilization of frogs, however, has been deleterious. As close-to-home sources of frogs became scarce, Indonesia and other tropical areas have been feeding the tremendous appetite for frog legs in Europe.
Demand is also growing in the United States. Between 1981 and 1984, the United States imported more than 6.5 million pounds (3 million kg) of frog meat each year, representing the death of approximately 26 million frogs. Most of these were harvested from the wild.
Frogs and toads are also killed for their hides. In Brazil, toads are fashioned into purses, and in Thailand, street vendors sell wallets made from frog skin. The capture of frogs and toads for the pet trade also has increased in recent years.
Amphibians absorb industrial and agricultural pollution from the air, soil and water. In addition, most amphibians eat huge amounts of insects, which often carry pesticides. Each year, farmers and gardeners in the United States buy more than 1 billion pounds (454 million kg) of pesticides to spray on their lawns and gardens.
In other places, like South America, chemicals banned in the United States are regularly used to increase yields from crops grown on poor soils. Not far from the home of the golden toad in Costa Rica, banana farmers liberally apply dangerous pesticides, to produce flawless bananas for markets in the United States.
Industrial pollution raining down from above causes the acidification of certain surface waters, even lakes and streams that seem far removed from human influence. Amphibians and their eggs are often the first animals to be affected by even slight changes in water pH.
In some studies, amphibian eggs subject to acid conditions failed to develop. Because acid rain can fall hundreds of miles from the source of the pollution, its effects are being felt in areas otherwise undisturbed by humans.
In the last two-hundred years, people have burned fossil fuels and cut down or burned forests at alarming rates. The resulting global warming has increased the Earth’s average surface temperatures and disrupted natural processes such as precipitation. Amphibians are sensitive to even slight changes in water temperature and their water-dependent reproduction can be devastated by drought or an ill-timed storm.
Unusually low rainfall in the two years before the reported disappearance of the Monteverde golden toad may have caused seasonal breeding ponds to dry up early, killing the toad eggs or young. Although amphibians have survived millions of years of weather change, including Ice Ages, it is thought that these human-caused climate changes are occuring too fast for amphibians to adapt.
A new theory on amphibian decline points to increased ultraviolet radiation (UVR) from the sun. High levels of UVR, such as might be caused by ozone depletion, have been shown to retard reproduction in amphibians and cause cancer. Populations of several frog species found in mountain habitats have declined dramatically.
These high-elevation species bask in the sun and are dark in color, adaptations to help keep the animals warm in cold conditions. These same tendencies may cause greater absorption of harmful radiation.
Researchers in Yosemite National Park surmise that introduced trout and bullfrogs have contributed to the decline of native amphibians. When the Park was first formed, sport-fishing enthusiasts stocked trout in many lakes which had no natural fish populations. Trout are both a predator of and competitor with the native frogs. The fish eat amphibian eggs and larvae and also eat the same insect prey as adult frogs.
The bullfrog (Rana catesbeiana), native to eastern North America, was widely introduced in the western United States in the late 1800s, presumably to increase available supplies of frog legs for restaurants. The bullfrog, which has thrived and spread, is known to eat and out-compete native frogs.
For amphibian populations already stressed by pollution, habitat loss, or other factors, the introduction of a new disease can be deadly. Scientists suggest that the mass disappearance of frogs seen in the Australian rain forest may be due to an epidemic of an exotic disease.
The increasing trade in plants and animals for aquariums may be transporting between continents diseases to which amphibians are particularly susceptible. Viruses or bacteria which may not be dangerous in their country of origin can be lethal to animals which have never encountered them before.
Perhaps amphibians are the “canary in the coal mine,” giving us early warning of the deterioration of our environment. If amphibians are the biological indicators of the world’s health, we need to pay attention to what they’re telling us.
Its beauty and rarity earned the golden toad fame rarely achieved by amphibians. It was used as a public relations symbol in the United States to raise money to purchase and protect its habitat, creating the Monteverde Cloud Forest Preserve in 1972. Although this action seemed to secure the toad’s future, it is now apparent that setting aside habitat is not enough to save most endangered species.
Amphibians continue to decline worldwide. Although the mystery has not been solved, it is likely due to a combination of causes. Amphibians will benefit from conserving tropical rainforests and other rare habitats, including wetlands, as well as strict controls on wild capture of frogs for restaurant consumption or the pet trade.
Reducing pesticide use and controlling the pollution that causes global warming will also help amphibians. It may be too late to save the Monteverde golden toad, but it is hoped that stepped-up research efforts will save other amphibians from the same fate.
A major step in protecting endangered amphibians is recognition of their plight. CITES Appendix I and II includes just ten species of frogs and toads for regulation of trade. Most of these are species sought after for meat.
The majority of amphibians affected by the pet trade are not yet protected under CITES. Few countries have targeted amphibians for protection. However, 12 domestic species of frogs and toads are listed under the Edangered Species Act)(ESA) in the United States.
The most recent addition is the California red-legged frog, listed as “threatened” under the ESA in May 1996. This frog, made famous by Mark Twain in The Celebrated Jumping Frog of Calaveras County, has disappeared from 70 percent of its former range. The listing is significant also because it is the first species of a backlog of 500 to be listed after the lifting of a year-long moratorium imposed by Congress.
Questions for Thought
Unlike beautiful birds and furry mammals, toads are not inherently appealing to most people. Why should we be concerned about the disappearance of one geographically-limited amphibian, like the Monteverde Golden Toad?
The Monteverde Golden Toad may live up to 12 years. No golden toads have been seen in the last seven years. Is it too early to say they are extinct?
CITES will not officially list a species as extinct until 50 years have passed since the last confirmed sighting. Is this standard appropriate for short-lived species like the golden toad? How might this standard affect golden toad conservation?
Words in bold italics can be found in the glossary.