April 26, 2013
You probably haven’t heard of the world’s second rarest ape, the cao vit gibbon. Scientists know of only one place the species still lives in the wild. In the 1960s, things got so bad for the cao vit gibbon that the species was declared extinct. But in 2002, to the surprise and elation of conservationists, the animals—whose shaggy coats can be a fiery orange or jet black—turned up along Vietnam’s remote northern border. Several years later, a few gibbons were found in China, too.
Also known as the eastern black-crested gibbon, the cao vit gibbons once covered an expanse of forest spanning from southern China and northern Vietnam just east of the Red River, but today only about 110 individuals survive. This gibbon is highly inclined to stick to the trees—in a previous study, during more than 2,000 hours spent observing gibbons in the field, researchers saw only once and very briefly one young male cao vit gibbon come down from the canopy and walk on a rock for a few seconds. Population surveys based on watching the animals in the branches reveal that the gibbons live in 18 groups scattered throughout the area. That makes it the second least populous species of ape, just after the Hainan gibbon, another type of extremely rare gibbon living in the same area of Asia.
In 2007 and 2009, Vietnam and then China hustled to establish special protected areas dedicated to preventing the cao vit gibbon’s extinction. Much of the area surrounding the remaining populations of gibbons is quickly being converted to agricultural fields and pasturesor cut down to make charcoal to sell and use at home, a common practice in the area. Hunting—though illegal—is also an issue, as exotic wild meat dinners are popular with locals in the region.
For an endangered species to recover rather than just survive, it needs to grow in numbers. But any given patch of land can only support so many animals given the amount of food and space that’s available. If populations exceed this threshold—called a carrying capacity—then animals will either starve, get picked off by predators or have to move somewhere else.
Researchers from Dali University in Yunnan, the Chinese Academy of Sciences in Kunming and the Chinese Research Academy of Environmental Sciences in Beijing wanted to find out how much of the protected forest the cao vit gibbons had expanded into, and also how many animals that pocket of land could eventually support. To answer this question, they turned to high-resolution satellite images, describing their results in the journal Biological Conservation.
Once they acquired aerial images of the gibbons’ habitat, they classified it into forest, scrub, shrub land and developed areas. This was important because gibbons can only live high in forest canopies, meaning the latter three categories were out of bounds for potentially supporting the animals. Overall, the area could be divided into five different zones that were split apart by either roads or rivers. From there, the researchers plugged the data into computer models that ranked possible gibbon habitat from high to low quality.
Their results revealed several bits of news, some good and some bad. First, from the models it seems that 20 groups of gibbons could eventually live in the protected forest areas before the population reaches its carrying capacity threshold. However, as human development creeps closer and closer, that disturbance could lower that figure. As things stand, the gibbons will likely reach their carrying capacity in the current habitat in 15 years, which doesn’t bode well for building up the species’ numbers.
There are a couple options. The protected area isn’t all great habitat, it turns out. Some of it is just mediocre for gibbons. If that span of forest could be improved, it could eventually support up to 26 groups of animals. The researchers also identified two other potential areas where gibbons could live if they could somehow manage to travel there (no gibbon has ever been known to cross a river or a road). But these patches of welcoming forest, located in Vietnam, are not protected, so they likely will not remain forests for long. If the government decided to protect those areas, the researchers write, they could serve as places for cao vit gibbons to live in the future, especially if narrow corridors of trees connecting the two areas were protected and restored as well.
If these patches of forest were protected, gibbons would not be the only species to benefit. Numerous other species of primates and monkeys, civets, pangolins, porcupines, birds, bats and many more depend upon those last remaining jungle habitats for survival. “In summary, the last remaining population of cao vit gibbon is nearing its carrying capacity in the current remaining forest patch,” the authors write. “Forest protection and active forest restoration using important food tree plantings to increase habitat quality and connectivity should be the most critical part of the ongoing conservation management strategy.”
March 4, 2013
When you think of an elephant, you probably picture a big-tusked bull stampeding through vast African grasslands. But there are more to elephants than this run-of-the-mill savannah variety. The African forest elephant—recently declared a distinct species from its plains-dwelling cousin–lives exclusively in the forests of Central Africa. Males rarely exceed 8 feet in height, compared to about 13 feet for savannah elephants–all the better for navigating through the jungle trees. They eat mostly fruit, and researchers think they play a key role in spreading seeds and shaping the forest’s environment and structure through their comings and goings.
But like many other animals living in Africa and Asia, this unique species is in decline as a result of rampant poaching for its ivory and loss of its forest habitat to human development. A new study led by the Wildlife Conservation Society and published in PLoS One puts those threats into perspective, and the news is not good. The situation for forest elephants is much worse than we thought, the paper announces, and unless we act quickly, the survival of these miniature elephants is in jeopardy.
Until now, conservationists had little idea of where exactly forest elephants live and how many of them there are. A team of 62 researchers from African, Europe and North America–the authors of the study–pooled their expertise and research efforts to figure out this basic information. Without these data, organizations such as the International Union for the Conservation of Nature (IUCN) cannot properly assess whether a species qualifies as endangered or not.
From 2002 to 2011, the team members conducted more than 80 forest elephant surveys in the jungles of Central Africa, focusing on five countries–Cameroon, Congo, the Central African Republic, the Democratic Republic of Congo, and Gabon. The scientists traveled on foot, covering around 13,000 kilometers of jungle. To determine elephant presence and density, the researchers set up transects to sample elephant dung, collecting more than 11,000 samples in total. Based on the amount of dung found, they extrapolated estimates of elephant population within a given area.
Their survey results were startling. They found “a widespread and catastrophic decline” of forest elephants, they write, corresponding to about a 62 percent decrease in forest elephant population size between the nine years of their survey. The elephants lost around 30 percent of their range during that time period, and they occupy just 25 percent of their potential forest habitat. The authors say that the population of forest elephants is now less than 10 percent of what it could be, given the extent of its habitat.
The paper conservatively estimates that around half a million forest elephants roamed Central Africa in the 1930s, but now 80 percent have been lost, leaving the population at an estimated 100,000 animals at most. In the Democratic Republic of Congo’s protected Okapi Faunal Reserve, for example, 5,100 elephants—75 percent of the park’s population—were killed over the past 15 years. In Gabon’s Minkébé National Park, officials announced earlier this year that roughly 11,000 forest elephants have been poached since 2004. The paper puts these reported losses into broad perspective.
“This is the first range-wide, data-driven study confirming that Central Africa is hemorrhaging elephants on an unprecedented scale,” said Samantha Strindberg, a researcher at the Wildlife Conservation Society and one of the study’s lead authors, in a statement. “The analysis confirms what conservationists have feared: the rapid trend towards extinction–potentially within the next decade–of the forest elephant, according to the authors.”
In the last few years, poaching for ivory and other wildlife products has escalated. Analyses performed by the Elephant Trade Information System and the Monitoring the Illegal Killing of Elephants program–both maintained by the Convention on International Trade in Endangered Species–confirmed that this escalation in illegal trade is largely due to a strong demand for and increase in value of ivory in China, where ivory carvings are prized and ivory powder is sold as a folk cure for cancer. The black market for ivory is estimated to have netted more than $264 million over the past decade.
While this problem is typically associated with slain savannah elephants, the growing crisis increasingly applied to forest elephants as well. In addition to the increase in price and demand for ivory, the authors add that:
The persistent lack of effective governance in Central Africa and a proliferation of unprotected roads that provide access to hunters combine to facilitate illegal ivory poaching, transport and trade. Forest elephant population and range will continue to decline unless conditions change dramatically.
Habitat loss, often to oil palm plantations for biofuel production, further exacerbates the problem, they write.
Given this dire situation, the authors call for the IUCN to add the African forest elephant onto their species Red List as Critically Endangered (the IUCN currently lists forest elephants as a subspecies of savannah elephants). This upgrade would draw international attention to the problem, the authors hope, which may help boost efforts and support to curb poaching. But reducing demand for ivory, the authors remind, remains the best way to ensure the survival of forest elephants and the countless other species impacted by the illegal wildlife trade.
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January 29, 2013
There are so many ways for a little bird or squirrel to die these days–they can be squished by cars, splattered into buildings, run over by bulldozers, poisoned or even shot. But if you have ever had to clean up a mangled “present” left on your doorstep by a kitty, you’ll know that little creatures can also be killed by pets.
Cats in particular have earned a nasty reputation for themselves as blood thirsty killers of wildlife. They have been named among the top 100 worst invasive species (PDF) in the world. Cats have also earned credit for countless island extinctions. Arriving onto the virgin specks of land alongside sailors, the naive native fauna didn’t stand a chance against these clever, efficient killers. All said, cats claim 14 percent of modern bird, amphibian and mammal island extinctions. But what about the mainland?
A recent study aimed to find out just that. Now the stats are in, and it’s much worse than we thought. But before bird lovers rush to declaw pets, the study’s scientists also found that feral cats and strays–not house cats–are responsible for the majority of the killings.
To arrive at the new findings, researchers from the Smithsonian’s Migratory Bird Center and the U.S. Fish and Wildlife Center assembled a systematic review of every U.S.-based cat predation study known in the scientific literature (excluding Hawaii and Alaska). Based on figures the authors verified as scientifically rigorous, they statistically quantified the total bird and small mammal mortality estimate caused by cats, further breaking the categories down into domestic versus unowned cats, that latter of which the authors define as barnyard kitties, strays that receive food from kind humans and cats that are completely wild.
Their results paint a grim picture for wildlife. In a paper published today in Nature Communications, they write that between 1.4 to 3.7 billion birds lose their lives to cats each year in the United States. Around 33 percent of the birds killed are non-native species (read: unwelcome). Even more startlingly, between 6.9 to 20.7 billion small mammals succumb to the predators. In urban areas, most of the mammals were pesky rats and mice, though rabbit, squirrel, shrew and vole carcasses turned up in rural and suburban locations. Just under 70 percent of those deaths, the authors calculate, occur at the paws of unowned cats, a number about three times the amount domesticated kitties slay.
Cats may also be impacting reptile and amphibian populations, although calculating those figures remains difficult due to a lack of studies. Based upon data taken from Europe, Australia and New Zealand and extrapolated to fit the United States, the authors think that between 258 to 822 million reptiles and 95 to 299 million amphibians may die by cat each year nationwide, although additional research would be needed to verify those extrapolations.
These estimates, especially for birds, far exceed any previous figures for cat killings, they write, and also exceed all other direct sources of anthropogenic bird deaths, such as cars, buildings and communication towers.
The authors conclude:
The magnitude of wildlife mortality caused by cats that we report here far exceeds all prior estimates. Available evidence suggests that mortality from cat predation is likely to be substantial in all parts of the world where free-ranging cats occur.
Our estimates should alert policy makers and the general public about the large magnitude of wildlife mortality caused by free-ranging cats.
Although our results suggest that owned cats have relatively less impact than un-owned cats, owned cats still cause substantial wildlife mortality; simple solutions to reduce mortality caused by pets, such as limiting or preventing outdoor access, should be pursued.
The authors write that trap-neuter/spay-return programs–or those in which feral cats are caught, “fixed,” and released back into the wild unharmed–are undertaken throughout North American and are carried out largely without consideration towards to native animals and without widespread public knowledge. While cat lovers claim that these methods reduce wildlife mortality by humanely limiting the growth of feral colonies, the authors point out that the scientific literature does not support this assumption. Therefore, such colonies should be a “wildlife management priority,” they write. They don’t come out and say it but the implication is that feral cat colonies should be exterminated.
But feral cats, some animal rights advocates argue, are simply trying to eke out a living in a tough, unloving world. As the Humane Society explains, simply removing the cats may not be the most efficient means of solving the problem because cats that are inevitably left behind repopulate the colony, surrounding colonies may move in to replace the old and “the ongoing abandonment of unaltered pet cats…can also repopulate a vacated territory.” Feral cats, after all, are the “offspring of lost or abandoned pet cats or other feral cats who are not spayed or neutered.” Targeting irresponsible humans may provide a different solution, although spay/neuter laws are controversial.
In Washington D.C. alone, for example, there are more than 300 known feral cat colonies. Wildlife are victims of this problem, but feral cats are too as conditions for survival are tough. And as with so many other environmental banes, the root of the problem neatly traces back to a single source: humans. As the authors write in their paper, feral cats are the single greatest source of anthropogenic (human-driven) mortality for U.S. birds and mammals.
January 14, 2013
Beneath massive communication towers, fallen bird bodies pile up like confetti. They collide with the steel structures—which can reach heights twice that of the Empire State Building—or fly into the miles of cables radiating around the beacons. Each year, nearly 7 million birds lose their lives to these web-like traps of wire and metal—27 times more birds than were killed in the infamous 1989 Exxon Valdez spill.
The killing season peaks during the time nocturnal migratory birds make their way between Canada and the U.S. Flying in the darkness, they spot the tower lights, become disoriented and begin circling the beams. After a storm, when natural navigational cues like the stars or moon are obscured, mortalities are particularly high.
While the magnitude of causalities is worrying, until now researchers did not know whether or not the avian victims were species of conservation concern or just common sparrows. Research recently published in the journal Biological Conservation, however, confirms scientists’ fears. Members of thirteen threatened North American species succumb each year to the towers. The fallen birds represent between 1 and 9 percent of those species’ total population numbers.
“Certain species of birds, including many already in decline, are killed at communication towers in far greater proportions than their abundance would suggest,” said lead author Travis Longcore, the science director of the Urban Wildlands Group and an associate professor of research at the Spatial Science Institute at the University of Southern California, in an email. “And it’s not just these thirteen species we have to worry about—they’re just the ones being killed at the highest rates,” he continued. “Many more species of concern are killed at lower rates, too.”
To figure out mortality by species and regions, Longcore and his co-authors constructed a database of species deaths based on verifiable, available records. Then, they calculated the mean proportion of each species killed and compared those statistics with overall mortality rates for each species’ total population in the U.S. and Canada.
All in all, they found, 97 percent of the birds being killed are passerines, or songbirds. Among the threatened birds that are dying are the Yellow Rail, with 2,200 annuals mortalities, representing 8.9 percent of the species’ total population; the Golden-winged Warbler, with 5,300 annual deaths, representing 2.5 percent of the population; and the Swainson’s Warbler, with 7,500 annual deaths, representing 8.9 percent of the population. Other species, though not currently of conservation concern, still suffer formidable losses. Red-eyed Vireos, for example, relinquish 581,000 lives to communication towers each year, and around 499,000 Ovenbirds die this way, too.
Last year, the same team found that around 1,000 of the towers, used for television and radio broadcast, are responsible for 70 percent of the bird deaths. Those 1,000 towers, the team noted, stand 900 feet or higher, representing the largest of North America’s 70,000-odd communication towers included in the original study. In their follow up study, they identified the deadliest sites, which are in Texas, Louisiana, Florida and the Midwest. The findings are no surprise; the Southeastern coastal plain and the Midwest regions contain the highest concentrations of the tallest towers on the continent.
The Migratory Bird Treaty Act of 1918 makes it illegal to kill migratory birds in the U.S., so the researchers hope their findings may be used to better regulate communication towers. Eliminating the steady-glow red lights from the towers and replacing them with blinking lights—the same fix adopted by the Federal Aviation Administration—may reduce bird mortality by 50 to 70 percent.
The study also carries another lesson, Longcore said. Simply counting up the total number of birds killed by wind turbines, cats, windows, pesticides or communication towers across the country and then making crude comparisons between mortality sources can be misleading, he pointed out. The most impactful data—the types of species killed, and where, and when and how—often lurk beneath those surface figures. “Simple estimates of total ‘bird’ mortality are insufficient; it matters which species are being killed,” he said. “Each mortality source may be significant, but for different species and in different places.”
September 19, 2012
In our October issue, Michelle Nijhuis joins wildlife biologists in searching Colorado’s caves and waterfalls for one of the world’s most mysterious bird species: the black swift. Although fewer than 100 breeding sites of the black swift are known, Nijhuis was lucky enough to see ornithologist Ron Torretta locate a black swift that had been geotagged in 2010, providing researchers with a cache of information about the wanderings of the enigmatic bird. Here are a few more of the most mysterious and elusive of the world’s bird species.
1. Night Parrot: Between 1912 and 1979, birders spotted this elusive species, native to the interior of Australia, exactly zero times—leading most scientists to believe it had gone extinct. Since then, a tiny handful of sightings of the nocturnal, yellow-green bird have occurred, and experts now estimate that the population is somewhere between 50 and 250 mature individuals. After the last verified sighting in November 2006, when park rangers in the state of Queensland turned up a decapitated specimen that had died after flying into a barbed-wire fence, the Australian government chose to keep the find temporarily secret while they searched for more night parrots, so as to avoid an influx of birders flooding the remote park in hopes of spotting one of the world’s rarest birds.
2. Ribbon-tailed Astrapia: Endemic to the forest highlands of Papua New Guinea, this bird has the longest tail feathers (in relation to body size) of any bird species, with feathers three times its body length. Unfortunately, this stunning plumage has enticed poachers; hunting, along with habitat loss, has led to the species being listed as “near threatened” by the International Union for Conservation of Nature. The species, the most recent bird of paradise to be documented, was first described by explorer Fred Shaw Mayer in 1938.
3. Palila: This species of Hawaiian honeycreeper has one particularly mysterious characteristic—it subsists almost exclusively on the seeds of the māmane plant, which contain a level of toxins that would kill any other small animal. Scientists aren’t sure how the birds digest the seemingly-lethal seeds, although the palila have been observed avoiding certain plants, indicating they might have a way of selecting seeds with lower levels of poison. In 1978, the federal government ruled that feral goats and sheep had to be removed from the palila’s only remaining habitat—the upper slopes of Mauna Kea on the Big Island of Hawai’i—since they consumed māmane plants and threatened the birds’ survival.
4. The Kakapo: Some 82 million years ago, the island of New Zealand broke off from what would become Australia, and the strange, flightless nocturnal parrot species called the kakapo began its unusual evolutionary path. In the absence of predators, it became the world’s largest type of parrot and lost the ability to fly; when European colonists introduced cats, rats and ferrets to New Zealand to control the population of rabbits, the kakapo was nearly wiped out. Now, just 126 wild kakapos live on three predator-free islands off the coast of New Zealand.
5. The Crested Ibis: Named for the crest of white plumage that extends from its nape, the crested ibis used to nest across Japan, China, Korea, Taiwan and Russia. By 1981, after years of habitat loss, just five individuals remained in the wild in Japan, and though scientists took the birds into captivity, a breeding program was unsuccessful. Now, the last remaining wild population—some 500 birds in the Chinese province of Shaanxi—is being buttressed by chicks hatched in captivity as part of a Chinese program. Although the species is still listed as endangered, scientists are cautiously optimistic that it is finally making a comeback.