by Scott Leslie
That July, George mated with one of his companions. Even though the female belonged to a different subspecies, any offspring would at least carry half the genes of the Pinta Island tortoise. The female laid about a dozen eggs. Excitement grew in the conservation community. But as time went by, it became apparent that the eggs weren’t developing as they should and were beginning to lose mass. Alas, in December 2008, it was announced the eggs failed. Another attempt in 2009 also was unsuccessful. Nobody knows for sure why. Was George infertile, or was the female? Or was it something else? In case the failure of the eggs has something to do with the female, there’s a $10,000 reward for anyone who finds George a suitable mate. The problem may be genetic incompatibility with the Isabela females. Based on DNA comparisons, scientists now think the Espanola Island subspecies may be more compatible with George. Two females were brought to live with him in 2011 in the hope that he will breed with them.
In the meantime, other scientists are taking a different tack in their effort to ensure the survival of the Pinta Island subspecies by looking for members of George’s subspecies among the large population of tortoises on Isabela Island. Although the island hosts different native subspecies, people have translocated tortoises from island to island over the centuries, so it’s hoped that at some point in the past, Pinta Island tortoises may have brought to Isabela. In 2007, DNA analysis revealed a male tortoise with half Pinta Island genes. It’s been determined that this animal is a first-generation hybrid offspring of an Isabela and a Pinta Island tortoise. So, there’s a chance that one of its parents, a pure subspecies of Lonesome George’s kind, might still be alive. Thus far, only a fraction of the 2,000 tortoises on the island have been tested. There’s still a chance more pure Pinta Island tortoises might exist.
Yet another possibility: Hundreds of Galapagos giant tortoises are found in zoos throughout the world. It’s possible that one or more of them might have been taken from Pinta Island a long time ago and shipped off to be put on display somewhere. It could be a tall order finding one, however, since there are thousands of zoos worldwide, as well as several saddleback tortoise subspecies, all of which look pretty much alike. Even with the help of DNA testing, this might be like finding a needle in a haystack.
RABB’S FRINGE-LIMBED TREE FROG
Frogs have been around for more than 300 million years, eclipsing the age of even the ancient cold-blooded reptilian order to which Galapagos giant tortoises belong. Not surprisingly, to get to where they are today, they’ve survived many of planet earth’s most violent doomsday events. First up was the Permian extinction that wiped out 95 percent of life in the oceans and 70 percent of life on land about 250 million years ago. Known as the “mother of all mass extinctions,” this low point in the history of life appears to have been caused by an asteroid slamming into the earth or global volcanic activity, or both. Then, beginning just a little later in geologic terms, the tectonic shift of the earth’s land masses caused the coming together and later splitting up again of the supercontinent Pangaea, 250 million and 175 million years ago respectively. After that, a momentous meteor impact ended the reign of the dinosaurs 65 million years ago. And last but not least, just 10 millennia past, the planet was shivering through a massive ice age. Somehow, frogs got through all of this, and today there are nearly 5,000 species to prove it.
But, for all their staying power in the face of such global cataclysms, frogs may have met their match in the form of a much smaller foe: a fungus whose diameter is about half the thickness of a human hair. First identified only in 1998, this mortal enemy of frogs, known as chytrid fungus, infects their unique skin, a highly porous membrane that helps them breathe and hydrate. The fungus blocks these functions, especially when infecting an area on the belly known as the “drink patch” where frogs take in water and essential nutrients known as electrolytes (sodium, potassium, magnesium, and so on). This often results in the quick death of the animal, though curiously, for some reason, certain species seem to have resistance to the fungus and are able to survive.
Scientists think chytrid fungus may have started to gain epidemic proportions at least as early as the 1970s and might be responsible for more than 100 extinctions of frog species since then. The disease is found in South, Central, and North America, the Caribbean, Australia, and Europe. Today, over 350 kinds of frogs are confirmed to be infected worldwide, with another 1,000 or so that are susceptible. That’s nearly one-third of all species. Although habitat destruction is still the largest threat to the survival of frogs worldwide, this disease is such a serious problem that an International Union for Conservation of Nature report in 2007 stated that chytrid fungus may be “the worst infectious disease ever recorded among vertebrates in terms of the number of species impacted, and its propensity to drive them to extinction.”15
Perhaps unsurprisingly, climate change might be involved in the severe nature of the epidemic and its spread, because warmer temperatures may be playing a role in weakening the resistance of frogs to the disease. Unfortunately, despite much research, nobody yet knows (as of early 2011) how to effectively stop the spread of chytrid fungus or how to treat those species already infected.
The frogs of Central America have been especially hard hit. The genus Atelopus, for example, a group of beautiful toads living in rainforests, has already seen 71 of its 113 species become extinct. Then there are the bizarre-looking fringe-limbed tree frogs, also victims of the fungus.
The Oaxacan fringe-limbed tree frog and Rabb’s fringe-limbed tree frog are large (up to 10 centimetres in length), arboreal frogs with oversized webbed feet, flat disks on the ends of their toes, and scalloped fringes of skin on their forearms. Both have been ravaged by the disease. The Oaxacan species hasn’t been seen for years in its southern Mexican habitat and may already be extinct. Rabb’s fringe-limbed tree frog, however, still hangs on by the slenderest of threads.
This amazing frog, though strange in appearance, is even stranger in habit. Using its big webbed feet and hands as air brakes, it can glide safely to the ground from high up in the forest canopy, where it spends most of its time. Its breeding habits are also bizarre. After the female has laid 60 to 200 eggs in a water-filled tree hole, the male takes over from her, first to incubate, then to rear the tadpoles. While taking care of the little ones, he allows them to engage in a bizarre form of cannibalism—on his own body. The tadpoles nibble on him, eating little flakes of his skin while he sits half submerged in water inside the tree hole.
Alas, it may be too late for this remarkable animal in the wild. It was already rare when first discovered as a brand-new species in 2005 at a few small sites in the mountainous cloud forests of central Panama. Chytrid fungus showed up the following year. The Rabb’s fringe-limbed tree frog may have already succumbed to the fungus by the time it was scientifically described, officially named, and its specieshood confirmed in 2008. At sites where the males were once heard singing in their habitat, they sang no more.
Fortunately, some frogs still exist in captivity. As insurance against the loss of the species, the El Valle Amphibian Conservation Center in Panama captured several of the frogs for captive breeding while a few could still be found. Zoo Atlanta and the Atlanta Botanical Garden are also involved in the program in the hope that the species’ population can be increased enough to stock former wild habitats in Panama. It’s likely the last chance of survival for the frog. Since there is only one female Rabb’s fringe-limbed tree frog in captivity, however, there is only one known female Rabb’s fringe-limbed tree frog on earth, so survival might be too much to expect.
In the meantime, the search continues, so far without success, for the species in its wild, native habitats in the mountains of Panama.
WYOMING TOAD
Like Rabb’s fringe-limbed tree frog, the Wyoming toad is also struggling to survive chytrid fungus. A relative newcomer to the world of frogs, it evolved when a population of Canadian toads was separated from its parent species by a glacier during the Pleistoc
ene era about 10,000 years ago. “Set adrift” on their own, isolated from the larger population by an ice sheet hundreds of kilometres wide, the toads continued to evolve in their southeastern Wyoming habitat. In doing so, natural selection had changed them enough genetically so that when the glaciers retreated 10 millennia ago, they could no longer breed with Canadian toads. But it didn’t matter. The nearest Canadian toad was 800 kilometres away. The Wyoming toad had become its own species.
This grey-brown, warty species was probably never widespread, living only in the Laramie Basin region of Wyoming. Nevertheless, the toad was quite common until the mid-1970s, when its population suddenly and inexplicably plummeted. It was listed under the US Endangered Species Act in 1984, and was thought to be extinct just a year later.
Happily, there is another chapter in the amphibian’s story. That’s because in 1987 a small population was found living in shortgrass habitat along the shores of Mortenson Lake, an alpine body of water located 24 kilometres from the city of Laramie. Apparently, the inconspicuous five-centimetre-long toads had been going about their little lives unnoticed here as they always had, eating beetles, ants, and other insects, burrowing into the soft dirt, and hibernating in abandoned ground squirrel holes. Because its mating trill is quieter than the familiar stentorian chorus of the familiar American toad, it isn’t surprising the Wyoming species wasn’t noticed earlier at Mortenson Lake. The beleaguered amphibian may have been down to just a dozen individuals by the time the lake became a small National Wildlife Refuge (NWR) in 1993, its sole purpose to protect the toad under the Endangered Species Act.
Although chytrid fungus, a deadly pathogen sweeping amphibian populations worldwide, is seen as the primary threat to the Wyoming toad’s survival, an important factor contributing to the early decline of the species appears to have been spraying for mosquitoes around the lakes of the Laramie Basin decades ago. Perhaps it’s no coincidence that Mortenson Lake, the species’ last refuge, is one of the few wetlands that wasn’t being dowsed with the insecticide fenthion—a chemical known to be deadly to frogs. Global warming may also be affecting this species, as droughts cause the evaporation of water from area lakes, making them saltier, something amphibians generally do not adapt to.
Mortenson Lake NWR continues to be the only place where Wyoming toads live outside a controlled, captive environment. In spite of this, the species is listed as extinct in the wild on the IUCN Red List, since, owing to the presence of chytrid fungus, the population at the lake can’t yet sustain itself through natural reproduction. So its survival there depends on the periodic injection of new captive-bred toads into the population. Today, thousands of young Wyoming toads are produced in captive breeding programs in zoos and wildlife research centres across the United States. However, until the secret of how to prevent wild Wyoming toads from being affected by chytrid fungus can be learned, and more suitable, safe habitats can be found in southeastern Wyoming, this little relict species from the last ice age might well remain extinct in the wild.
THERMAL WATER LILY
Although saved from complete extinction by a German botanist, the thermal water lily, in contrast to expectations for the Wyoming toad and several other extinct-in-the-wild species, may never have the option of returning to its native habitat someday.
Discovered in 1986 by biologist Eberhard Fischer of Germany, the tiny water-loving plant, whose little white flowers and pads are a mere one centimetre in diameter (the largest water lily, native to the Amazon, has pads three metres across), lived around a single 40 degree Celsius hot spring in Mashyuza, southwestern Rwanda. It grew only along the damp edges of the spring, occupying just a few square metres. Its total world population was as few as 50 plants.
Fischer, seeing how much local people used the hot spring, thought the water lily was in jeopardy, so he collected some specimens just in case its only habitat was destroyed. The specimens ended up back in Germany at the Bonn botanic gardens. It turned out that Fischer’s concern for the future of the plant was well founded: people in Mashyuza exploited the hot spring heavily, ultimately diverting it to irrigate crops. This prevented water from reaching the water lily’s habitat, which soon dried up. By 2008, the IUCN declared the species extinct in the wild.
But a few of Fischer’s plants still hung on at the Bonn botanic garden, where they survived for over 10 years, though horticulturists there were unable to propagate any new ones. It appeared the thermal water lily was doomed to disappear for good. Then, in 2009, when only a single plant survived, a handful of seeds from the seed bank at the botanic garden were sent to Kew Gardens in London. Maybe they’d have better luck cultivating the world’s smallest water lily. This weighty task—the fate of a species—would be in the hands of Kew horticulturist Carlos Magdalena.
Unlike other water lilies, this species didn’t root in deep water; instead, it lived in muddy areas warmed by the hot spring. As a result, Magdalena, described by Kew Gardens as a top “code-breaker” when it comes to figuring out how to cultivate unusual or rare plants, worked for months to find the secret of propagating the thermal water lily. He finally cracked the code by placing the seeds and seedlings in moist soil surrounded by 25 degree Celsius water. They began to grow. A turning point was reached in November 2009 when the first cultivated plants flowered. Now, with its propagation technique established, dozens of new plants have been cultivated.
Magdalena hopes to one day return the species to its original habitat in Rwanda so that it might grow wild again. The question is, will there be any habitat left to return it to? So saving the organism itself from oblivion is only half the battle because, like every other species on the planet, it needs a place to live.
12.Rota is also home to the only wild Mariana crows in existence, another Guam native species ravaged by the snakes.
13.Charles Darwin, Voyage of a Naturalist Round the World in the HMS Beagle (London: George Routledge & Sons, Limited, 1860), 394.
14. Darwin wasn’t the only person to discover that life evolves by the process of natural selection. Alfred Russel Wallace, an unrecognized naturalist and specimen collector, came up with the same idea independently at roughly the same time as Darwin while collecting animal specimens in the jungles of Indonesia—at the time known as the Malay Archipelago. In fact, Darwin’s and Wallace’s papers on evolution were presented together at a meeting of the Linnean Society of London in 1858. Popular history has largely neglected Wallace, and Darwin got credit.
15. Amphibian Conservation Action Plan, proceedings of the IUCN/SSC Amphibian Conservation Summit 2005, ed. Claude Gascon et al. Gland, Switzerland: World Conservation Union.
PART THREE
COMEBACKS: UNDER 100 AND BACK AGAIN
The stories that follow tell us that extinctions aren’t preordained. They show what can be accomplished when the best human qualities express themselves: knowledge, foresight, effort, optimism, perseverance, and, most importantly, selfless love and compassion that transcends species boundaries. It took all of this, plus the necessary economic resources, to reel these animals back from the brink of extinction. Although each one of them might have been considered by many as a lost cause (hearken back to the fatalistic and false belief that the dodo went extinct because it was unfit for survival), a few conservationists refused to give up on the futures of these living things whose histories are much older than ours. And they succeeded despite the odds. After a lot of hard work, every one of these endangered animals has been wrested from oblivion, from populations in the wild as low as 5 individuals to over 100 today; in some cases, well over that number.
WISENT (EUROPEAN BISON)
Prehistoric Europeans took early notice of the wisent (pronounced vizent). It should come as no surprise that an animal hefting enough meat to feed an entire village for a week would pique their interest. Its value to early inhabitants is evident in the 17,000-year-old paintings of it (or a very similar species) on the cave walls of Lascaux in southwestern France.
Weighing up
to nearly 1,000 kilograms and measuring over two metres in height, the wisent is Europe’s largest land animal. Closely related and similar in appearance to the American bison, the slightly smaller European species is a forest dweller rather than a strictly grassland animal like its better-known cousin. It is more similar, in fact, to the less-well-known wood bison of Canada’s boreal forest. Living in small herds of about 10 to 30 animals, the wisent inhabits deciduous and mixed deciduous-evergreen woodland, with a bit of grassy meadow mixed in. In contrast to most large hoofed mammals, which are grazers, the wisent are largely browsers, eating leaves, twigs, bark, saplings, and the berries of several hundred plant species, along with just a little grass.
Heavy hunting over thousands of years and the accelerating destruction of its forested habitats by an expanding European population had decimated the population, creating perfect conditions for extinction. The species was already gone from the British Isles, Sweden, and the Iberian Peninsula by the 1500s. The remaining stronghold of the wisent was in the Bialowieza Forest in Poland, the last primeval forest wilderness left in central Europe. Fortunately for its wildlife, Bialowieza was owned for centuries first by Polish kings, then by Russian royalty (Catherine the Great took control of this part of Poland in the third partition of the country in 1795). In the first recorded edict protecting the forest, Polish king Sigismund I in 1538 decreed the death penalty for anybody poaching a wisent. Naturally, the nobility’s motivation in protecting wildlife wasn’t altogether altruistic: they simply desired a large stock of animals for them and their friends to hunt. These aristocratic wildlife “owners” employed large contingents of indentured guards to protect the animals from poachers. In spite of this, by 1812 only 300 to 500 bison remained, along with another very small population of a separate mountain subspecies in the Western Caucasus Mountains of Russia.