The allure of anteaters: attracting increased attention from scientists and the general public alike, these endearing creatures are "ambassadors" for wildlife conservation and research.
That giant anteater was one of 75 or so that the scientists caught and outfitted with radio collars during a three-year study of anteater ecology and behavior. Shaw, now a professor of wildlife biology at Oklahoma State University, wanted to know how many anteaters lived in that part of the Brazilian savannah, how they interacted with others of their own kind, and what they are. At the time. in the late 1970s and early 1980s, little was known about anteaters. Although somewhat better understood today--thanks to research by Shaw and other US and Brazilian scientists--anteaters are still one of the most understudied and least known animals in the Americas.
What is known about anteaters paints the critters as among the world's strangest animals. Consider the following: With a small head and mouth and elongated snout, they look funny. By walking on the insides of their feet, which protects their claws from wear and tear, they have an awkward gait. Feeding on ants and termites, they have a weird diet. And, perhaps befitting animals that eat insects, they have a lower body temperature and metabolism rate than any other mammal of their size. They even have unusual sexual and reproductive organs.
Despite--or maybe because of--all those features, anteaters are also one of the more appealing and beautiful of Latin American animals. Apparently, wildlife biologists, conservationists, zoo curators, and the general public are beginning to think so too. Anteaters are the subject of increasing research by scientists who are extending our knowledge of the animals, attention by conservationists who worry about their future, and interest among zookeepers and zoo visitors alike.
There are four species of anteaters, all native to Central and South America. Giant anteaters, the largest of the bunch, weigh up to 85 pounds and measure four to six feet in length, half of that made up of a long, bushy tail. Striking creatures, they are mostly grayish in color with a black-and-white stripe that runs from the front of the head past the shoulders. Giant anteaters can be found in tropical forests as well as grasslands from Honduras and Guatemala to northern Argentina.
Next come the lesser or collared anteaters. Here, scientists recognize two separate species--northern and southern. Called tamanduas in Central and South America, they are less than half the size of their giant cousins. Their coloration ranges from mostly brown with a black collar around their back, shoulders, and middle in northern tamanduas to a gold, brown, and white pattern in the southern species. Unlike giant anteaters, which are mostly ground-dwelling animals, tamanduas spend much of their time in trees. They can be found from southern Mexico to Uruguay.
The smallest and least known of the four are the squirrel-sized silky anteaters. Measuring only twelve to nineteen inches long and weighing but ten to seventeen ounces, silky anteaters are rarely seen and little studied. About the only time they are spotted in the wild is when someone cuts down a tree and a silky anteater gets up from the fallen trunk or limbs and walks away. They inhabit the densest tropical forests from southern Mexico to northern Peru and the Amazon basin. Silky anteaters are strictly nocturnal, spending virtually all of their time aloft. Their hair is a golden yellow in the northern parts of their range, but becomes progressively grayer to the south.
If anteaters are strange, so too are their relatives, the sloths and armadillos. All belong to a group of mammals taxonomists have classified as edentates or animals "without teeth." That's a misnomer, actually, since only anteaters truly lack teeth. Instead of teeth, anteaters have horny protrusions called papillae on the roofs of their mouths and strong, muscular stomachs. Sloths and armadillos both have teeth, but only primitive molars with no canines, incisors, or premolars. To correct the name, some taxonomists now classify anteaters, sloths, and armadillos as xenarthra ("foreign" or "strange" joints).
Moreover, unusual for mammals, anteaters and some sloths and armadillos have simple skulls, a double rear vena cava (the vein that brings blood from the lower body back to the heart), and--at least in the females of some species--a divided womb. Females also have a joint urinary and genital tract, a characteristic shared with primitive mammals such as the monotremes of Australia. For their part, males have internal testes and, in some edentates, small penises with no glans.
As unusual as modern edentates may be, they pale in comparison with some of their extinct relatives. Take the giant ground sloths, some of which were as big as today's elephants. Unlike modern tree-dwelling sloths, giant ground sloths were, as their name suggests, purely terrestrial. They ranged from Patagonia in South America to the southern and southwestern United States. Additionally, the glyptodonts were armadillo-like animals that measured up to sixteen feet long and carried hard, turtle-like shells on their backs, the only mammals so protected. Some also had tails equipped with armored tips that looked like medieval maces. Both giant ground sloths and glyptodonts disappeared after the last Ice Age about 10,000 years ago, but the Tehuelche mad Araucan indigenous peoples of Patagonia still speak of them in their legends.
One thing about anteaters that should not seem strange is the fact that they exist at all. Their main prey--ants and termites-are ubiquitous in the world's tropics. In some places, ants and termites constitute up to one-third of the total weight or biomass of all living animals. In fact, the estimated weight of all ants worldwide is greater than that of all people. Most of the nearly 12,000 known species of ants and 2,600 of termites live in the tropics. In Latin American, African, and Australian tropical grasslands, the mounds they build literally cover the ground. Some animals were bound to evolve to take advantage of such a plentiful food source, so why not anteaters?
That same logic helps explain why anteaters are not found today in North America or the southernmost parts of South America; relatively few ants and termites live in those colder climates. "You can't make a living [eating ants and termites] in North America," says Brian McNab, professor of zoology at the University of Florida. "If you're an anteater, what do you do in the winter?" Unlike some northerly animals, anteaters do not hibernate (although at least one South American armadillo does) or enter a state of torpor.
By the way, Shaw found that catching giant anteaters is neither as difficult nor as simple as one might think. Because of their awkward walk, anteaters do not run fast. Nor do they see well. Thus, they can be approached from behind if the wind is blowing right. People can also outrun them. Be careful, though: those forearms and claws can kill a dog or seriously injure a human. They also apparently can scare off would-be predators. Shaw reports never seeing a jaguar or cougar, the main large predators in South America, attack a giant anteater during his three years in Brazil.
On the other hand, ask James Dietz how dangerous anteaters can be. Dietz, a professor of biology at the University of Maryland, was studying maned wolves in the Brazilian cerrado when one day he volunteered to help his friend Shaw capture giant anteaters. Dietz got too close to one he thought had been tranquilized. The anteater awoke and reached up, scratching Dietz with its back leg and digging a claw into his arm. Dietz howled, let go of the anteater, mad later treated the wound with the only thing available miles from the nearest medical help--Brazilian rum.
Let's pause here for a minute and distinguish between anteaters and ant eaters. While anteaters are Latin American animals, a number of animals around the world eat ants, termites, and other such insects. Some even look similar to giant anteaters. These include the aardwolves of Africa, the aardvarks ("ground pig" in Afrikaans) and the pangolins of Africa and Asia, and the numbats and echidnas, primitive egg-laying mammals of Australia. They are all mammals, but none are closely related to Latin American anteaters.
Eating ants mad termites "is all anteaters know how to do today," observes Kent Redford, a conservation biologist and director of the Wildlife Conservation Society Institute, an arm of the Bronx Zoo in New York. "They're extremists," says McNab, speaking of anteaters and other animals with the same diet. "They are really committed behaviorally and physically [to eating ants and termites]. They are locked in to an ecological niche that is an evolutionary dead end." That may sound a bit negative, but McNab insists, "I love anteaters. It is really fun to watch them at work."
"At work" refers to how giant anteaters attack ant or termite colonies. Anteaters slowly amble up to an ant or termite mound, carefully sniffing--they are said to have a sense of smell 40 times as sensitive as that of people--to make sure that it contains one of the few species of insects anteaters prefer. Individual anteaters eat only about a half dozen of the thousands of ant or termite species that inhabit the Latin American forests and grasslands. While different anteaters prefer different ants, they usually avoid army ants and other species with large, biting jaws or particularly potent chemical defenses. When they find the right ones, giant anteaters sit down on their haunches, use their powerful forearms and claws to rip open the mound, and then lap up the insects with their long tongues.
Redford thinks that anteaters select the species they eat based on which ones are most abundant and how much work they have to do to get their prey. Thinking about which mats or termites to eat probably does not occur to the critters, however. "Anteaters are not very smart animals," he says. Pointing to their small heads and relatively small brains, Redford adds: "I think they don't think about much at all."
If not brains, what anteaters do possess is a tongue that may be the envy of the animal world. They can extend their tongue up to two feet in length, flicking it in and out of their mouth 150 times a minute. The sheath that holds the tongue and the muscles that control it are anchored to the animal's breastbone. And their salivary glands produce enormous quantities of a sticky substance that traps their prey. No one knows for sure how many ants or termites anteaters eat, but some estimates suggest it may be as many as 30,000 a day. However many, anteaters also consume a lot of what McNab calls "junk" in each mouthful--sand, soil, and plant material. For their part, ants and termites are not defenseless against anteaters. Their colonies are protected by a caste of workers--called soldiers--with big bodies and large, powerful jaws. Within a minute or two of an anteater attack, hundreds of soldier ants or termites rush out to defend the colony. They climb all over the anteater and, depending on the species, bite the attacker or spray noxious chemicals all over its body. The latter include limonene and pinene, chemicals that smell good to people, Redford says, but are probably toxic to anteaters. "Anteaters can only take so much," McNab observes, noting that they typically give up after a few minutes and move oil to another ant or termite mound.
Perhaps because they dine almost exclusively on an abundant but poor-quality food, anteaters have a low metabolic rate and body temperature, McNab says. With bodies that burn fewer calories, anteaters have metabolic rates that are only 33-60 percent those of other mammals. Their body temperatures range from 91-95[degrees]F. Most mammals their size have body temperatures of 95-100[degrees]F. Almost all ant eaters worldwide also have low metabolic rates and body temperatures, McNab adds. Similarly, sloths have body temperatures that range from 86-93[degrees]F and metabolic rates 40-45 percent that of other mammals their size. Low metabolic rates and body temperatures help explain why anteaters sleep fourteen hours a day and move slowly.
Further, the ratio of ants and termites that giant anteaters eat may differ from place to place, Shaw says. Earlier studies had found that anteaters in Venezuela are more termites than ants. In Brazil, however, Shaw found the ratios reversed: There, anteaters consume more ants than termites. "They are very adaptable," he says of anteaters. Because they are more arboreal than giant anteaters, tamanduas and silky anteaters feed mostly on ants and termites that nest in trees. Giant anteaters will occasionally climb trees to get at arboreal insects.
Previous studies had also shown that giant anteaters in Venezuela have large home ranges that they share with other anteaters. Those Shaw studied in Brazil, however, have smaller home ranges that they defend against other anteaters. He thinks the greater density of anteater populations living in the Brazilian cerrado forces the animals to divide the habitat more strictly. And, while earlier studies had found giant anteaters are nocturnal in Venezuela, Shaw discovered they are active in the afternoon and evening in Brazil.
Such oddities have made anteaters a wonderful attraction for zoo goers, says Roberto Aguilar, director of conservation and science at the Photo,ix Zoo in Arizona. The question is what to feed them. Although some zoos give their anteaters ant- or termite-filled hollow logs to tear apart, they cannot possibly provide enough insects to equal what the animals would naturally consumer in the wild. As a result, captive tamanduas fed cat food developed fused vertebrae and other deformed bones as well as diarrhea and blood in their stools. Researchers found their zoo diets were too rich in vitamins A and D. Partgolins, echidnas, and other ant-eating animals in zoos have similar illnesses related to their diets. The tamanduas' health improved after milk was removed from their diets and vitamin E and K supplements were added, says Ellen Dierenfeld, the St. Louis Zoo's nutritionist.
More seriously, in the 1990s captive giant anteaters in several US, European, and Latin American zoos became lethargic and had trouble sleeping and breathing, Aguilar says. More than a dozen died. Autopsies showed the animals suffered from cardiomyopathy, a condition common in cats in which the heart becomes enlarged, rounded and weak. After studying giant anteaters at the Phoenix, Miami, and New Orleans zoos, Aguilar concluded the animals lacked tanfine in their diets. Taurine is an amino acid found naturally in chitin, which forms the exoskeleton or outer shell of insects. It is also found in high-protein human foods, energy chinks, and dietary supplements.
To resolve the nutritional deficiency in anteater diets, Aguilar and others took food that zoos feed to insect-eating animals, mixed in some dog food, yogurt, and taurine supplements, and added the heads of shrimp to provide the chitin anteaters would normally get from consuming ants and termites. It worked. Sick anteaters slowly recovered as taurine was added to their diet, Aguilar says, and no additional animals have since died. Many zoos also now feed their anteaters soft fruit like oranges, bananas, or avocados, as well as eggs, which the animals mash with their claws and then lap up with theft" tongues.
Beyond diet, simply keeping anteaters--let alone breeding them in captivity--is not easy, says Con[fie Philipps, director of animal collections at the Nashville Zoo, which has ten giant anteaters. Of ten giant anteaters born at Nashville, three died. One was killed by an adult anteater, while two others cried during birth. The latter were larger than most anteater babies, leading Philipps to wonder: "Maybe we fed their mothers too well." The Nashville Zoo also found anteaters are easily stressed by noise. The zoo has put up signs asking motorists not to honk their horns and visitors to turn off their cell phones, both of which seem to disturb anteaters. The zoo also keeps construction noise down near the anteater exhibit and plays soothing music inside the building.
Those steps are apparently working. There are now more than 90 giant anteaters in 30 US zoos plus 41 southern tamanduas, says John Gramieri, mammal curator at the San Antonio Zoo and head of the American Zoo Association's anteater advisory group. More than three-quarters of those were born in zoos. "We want to get ahead of the curve by breeding them in captivity before they become endangered," Philipps states.
It's a good thing, too, since some trends speak ominously about anteaters' prospects in the wild. None of the four species are listed as endangered by the International Union for the Conservation of Nature (IUCN), but the giant anteater was so designated by the Brazilian Environment Ministry in 2003. Anteaters suffer habitat loss when people cut down tropical forests to create pasture for cattle and burn grasslands to grow crops. That plus subsistence hunting destroys anteater habitat and reduces their numbers, says John Aguiar, coordinator of the IUCN's edentate specialist group and editor of the scholarly journal Edentata. Aguiar says anteaters and other edentates should be protected because they are physiologically similar to the earliest placental mammals, thus telling us a lot about ancient mammals and mammalian evolution.
"Giant anteaters are charismatic animals," Gramieri says, explaining the importance of zoo programs to display and breed them in captivity. "If we waited until they were endangered, we would have waited too long. We can help mold public empathy for these creatures. Anteaters are ambassadors for wild animals and the ecosystems to which they belong. Our job is to help foster anteater conservation and research."
Several groups are working to study and protect anteaters in the wild in Latin America. The IUCN, for example, helps support two such efforts in Brazil: One is a conservation program of the Sao Paulo Zoological Park Foundation that seeks to preserve silky anteaters; the other is Projeto Tamandua a small Brazilian nongovernmental organization that promotes giant anteater conservation and research. For its part, the St. Louis Zoo is helping Nicaragua's Bosawas Biosphere Reserve protect anteaters, Dierenfeld says.
Giant anteaters "are so terrific," says Flavia Miranda, Project Tamandua's coordinator and marketing director for the Brazilian Association of Wild Animal Veterinarians (ABRAVAS). "There is a lot of fantasy and prejudice about them. We have to protect them."
RETURN OF THE ARGENTINE ANTEATER
by Colin Barraclough
IN ARGENTINA'S NORTHERN province of Corrientes, an ambitious effort is underway to reintroduce a locally extinct population of giant anteaters, with the goal of restoring the animal's full distribution range.
The giant anteater once thrived in the Esteros del Ibera, a wildlife-rich wetland in Corrientes. Large populations of yacare caiman, howler monkeys, capybaras, and marsh deer inhabit the region's marshes, lakes, and floating "islands," huge mats of peaty silt caught in the entwined roots of water hyacinths.
Over the past century, however, habitat loss, attacks by domestic dogs, and unchecked poaching sent the anteater population into steep decline. While the animal survived in grasslands, woods, and jungles in other Argentine provinces, by the 1960s it had effectively disappeared from Corrientes.
In May 2007, however, Governor Arturo Colombi opened a cage containing a two-year-old female anteater, nicknamed Iboty pora or "beautiful flower" in Guarani. The symbolic release saw the animal freed into a specially constructed pen enclosing a large tract of savannah, where it will learn to adapt to its natural habitat before gaining complete freedom.
The release was part of a project run by the Conservation Land Trust, a nonprofit ecological organization run by Doug and Kris Tompkins, a North American couple who have bought large tracts of land in Argentina and Chile in order to conserve fast-disappearing natural habitats.
In 1999, the trust bought 888 square miles of marsh and savannah in the Esteros del Ibera. Its directors turned the central property, Estancia Rincon del Socorro, a former cattle ranch, into an upmarket hosteria for paying guests and set about protecting and restoring the region's delicate ecosystem. Keen to reinsert the giant anteater to its once-native habitat, they sought permission from wildlife authorities in Corrientes to relocate specimens from other parts of Argentina to the wetlands.
Yet legal restrictions designed to protect endangered species actually complicated these efforts. Legal precedents for the reintroduction of native species in Argentina extended only to nonthreatened mammals, such as the guanaco, and to certain native bird species, such as the lesser rhea, the Andean condor, and the flamingo. The proposal to reintroduce the giant anteater was, in effect, the country's first legally authorized reintroduction of an endangered mammal species.
As such, the trust was determined to establish an environmental and legal model for others to follow. "It was an enormous challenge," said Kris Tompkins. "The country was watching closely, so we wanted to do it right."
The first animal designated for release came from the northwestern province of Jujuy, where it had been rescued and cared for by a local family after sustaining injury. In March, it was sent to Corrientes, where it underwent a series of medical tests while in quarantine at a government-run animal center before its final transportation in May to Rincon del Socorro. Two male anteaters were subsequently released in June.
The Conservation Land Trust intends to reintroduce several more specimens a year for at least a decade, in order to build a genetically mixed, disease-free anteater population. Its scientists are currently evaluating the health and genetic imprint of ten other anteaters located in the provinces of Buenos Aires, Salta, and Santiago del Estero.
"There are many cases of anteaters kept in captivity in people's homes," said Sofia Heinonen, a biologist working on the project. "Some smaller zoos also have specimens which they are unable to care for properly. In the past, no one really knew what to do with them. Not any more. Now that we've set a precedent, they can come to Corrientes."
Jeffrey P. Cohn is a regular contributor to Americas on science and conservation issues.
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|Author:||Cohn, Jeffrey P.|
|Publication:||Americas (English Edition)|
|Date:||Nov 1, 2007|
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