The striking white Lipizzaner stallions of the famed Spanish Riding School in Vienna have been thrilling audiences for centuries. During the winter public performance season, the horses execute breathtaking displays of carefully choreographed and synchronized movements known as high classical dressage. The riding school’s success relies on the strong bonds the animals establish with their riders during years of training; Lipizzaner stallions go through a minimum of six years of practice and preparation before performing publicly. Legendary White Stallions explores how Lipizzaners have developed from horses bred for war in the rugged Atlas Mountains of North Africa into living works of art capturing the hearts of millions in a world-famous court of kings. “Legendary White Stallions” premieres Wednesday, May 1 at 8/7 check local listings).

Eels: An Exploration, From New Zealand to the Sargasso,
of the World’s Most Mysterious Fish

by James Prosek

 
Conjecture about what an eel is exactly, or where its place is in the tree of life, has racked the brains of more than a few naturalists. Its limbless elongated body led some to believe it was related to the snake. The Greek naturalist and poet Oppian wrote in the second century A.D.: “Nothing more is known, than what people repeat about the loves of Roman eels and snakes. Some say that they pair, that, full of eagerness, drunk with desire, the Roman eel comes out of the sea to go and meet her mate.” As late as 1833 Jerome V. C. Smith wrote in his Natural History of the Fishes of Massachusetts: “On the whole, we view the eel in the light of a water-serpent, being the connecting link between purely aquatic and amphibious reptiles.” The eel, however, is a fish, though it is a fish like no other.

The freshwater eel, of the genus Anguilla, evolved more than fifty million years ago, giving rise to fifteen separate species. Most migratory fish, such as salmon and shad, are anadromous, spawning in freshwater and living their adult lives in salt water. The freshwater eel is one of the few fishes that does the opposite, spawning in the sea and spending its adulthood in lakes, rivers, and estuaries—a life history known as catadromy (in Greek ana- means “up” and cata- means “down,” that prefixes suggesting the direction the fish migrates to reproduce). But among caradromous fishes, the eel is the only one that travels to the depths of the oceans so far offshore.

“Salmon,” Mike Miller, an eel scientist, told me, “can imprint on a river system. They are born in the river system, they go out in the ocean, and they come back to the same river—it’s not that bloody hard to do. In the case of the eel, you’re born in the open ocean. You can’t see anything around you except blue water. It’s just blue water until they come to the coastal areas, where they first enter estuaries and streams at random. And then, ten to thirty years later when they leave the river, they have to swim all the way out to the same place in the ocean again. And how do they do that?”

The American and European freshwater eels (Anguilla rostrata and Anguilla anguilla) emerge from eggs suspended in the ocean—specifically, the western part of a subtropical gyre in the North Atlantic somewhere east of Bermuda called the Sargasso Sea. The only reason scientists know this is that baby eels in their larval stage, called leptocephali, have been found drifting near the surface of the ocean thousands of miles from any short. No one has ever been able to find a spawning adult or witness a freshwater eel spawning in the wild. For eel scientists, solving the mystery of eel reproduction remains a kind of holy grail.

Wherever eels are born, they’re relentless in their effort to return to their oceanic womb. I can tell you this from personal experience because I’ve tried to keep them in a home aquarium. The morning after the first night of my attempt, I found eels slithering around the floor of my kitchen and living room. After securing a metal screen over the tank with heavy stones, I was able to contain them, but soon they were rubbing themselves raw against the screen. Then one died trying to escape via the filter outflow. When I screened the outflow, they banged their heads against the glass until they had what appeared to be seizures and died. That’s when I stopped trying to keep eels.

Eels are wondrous in their ability to move. They’re often found in lakes, ponds, and postholes with no visible connection to the sea, leaving the inquisitive shaking their heads. On wet nights, eels are known to cross over land from a pond to a river, or over an obstruction, by the thousands, using each other’s moist bodies as a bridge.Young eels can climb moss-covered vertical walls, forming a braid with their bodies. Farmers in Normandy say that eels will leave rivers on spring nights and find their way to vegetable patches to feed on peas.

The yearly journeys of millions of adult eels make from rivers to oceans must be among the greatest unseen migrations of any creature on the planet. In the course of these journeys, which span thousands of miles, eels face a long list of dangers: hydroelectric dams, river diversions, pollution, disease, predation (by striped bass, beluga whales, cormorants, among others), fishing by humans, and changes in ocean currents or temperature structure due to global warming, which may confound eels during their migrations.

From Aristotle through Pliny, Walton, and Linnaeus, great naturalists through time have put forward various theories as to how eels make new eels—that the young emerged from the mud (Aristotle); that eels are bred from a particular dew that falls in the months of May and June (Walton); that they multiplied by rubbing themselves against rocks (Pliny)l that they were viviparous, bearing live young rather than laying eggs (Linnaeus). One problem was that no one could identify sperm or eggs in eels. Over a forty-year period in the late 1700s, at the famous eel fishery at Comacchio, Italy, the biologist Spallanzani calculated that more than 152 million adult migratory eels had been caught and cleaned, not one of which was found to be pregnant. No one could say for sure whether eels even had gender, because no one could identify their reproductive organs.

In the late nineteenth century, a young medical student named Sigmund Freud was assigned by his professor Carol Claus to investigate what had been postulated to be the testes of the male eel. During several months at the Zoological Experimental Station in Trieste, Italy, Freud dissected more than four hundred eels, looking for loops of white matter festooned in the body cavity. His 1877 paper on eels, “Observations on the Form and the Fine Structure of Looped Organs of the Eel, Organs Considered as Testes,” was Freud’s first published work. One can’t help but wonder if the time he spent that summer in his twentieth year dissecting eels played some role in the development of his later psychosexual theories.” Needless to say, the testes of the eel would not be confirmed until 1897, when a sexually mature male eel was caught in the Straits of Messina between mainland Italy and the island of Sicily.

The larval stage of the eel bears little resemblance to the adult#&8212;it is a tiny, transparent creature with a thin head, a body shaped like a willow leaf, and outward-pointing teeth. The larvae of freshwater eels were originally thought to be that of a separate genus of fish, first described as Leptocephalus breverostris in 1856 by the German naturalist Kaup after a specimen from the Mediterranean Sea (the common name for eel larvae today, leptocephali, remains as a relic of this misnomer.) Then in 1896 two Italian biologists, Grassi and Calandruccio, watched a Leptocephalus breverostris metamorphose in a tank into an eel#&8212;the most convincing evidence to support the theory that freshwater eels were born in salt water. Still, though some speculated that eels spawned in the Mediterranean, no one had yet dreamed that freshwater eels from Europe hatched in the middle of the Atlantic Ocean.

In 1904, James Schmidt, a young Danish fisheries biologist, got a job abroad the Thor, a Danish research vessel, studying the breeding habits of food fishes such as cod and herring. One day in the summer of that year, a tiny fish larva showed up in one of their find-mesh trawls, west of the Faroe Islands in the Atlantic Ocean. Based on the number of vertebrae, 115, and the hypural bones at the end of teh vertebral column, Schmidt identified the larva as that of the European eel, Anguilla anguilla, the first to be recognized as such outside of the Mediterranean Sea.

A year before, Schmidt had made an auspicious betrothal to the heiress to the Carlsberg Brewery, A Danish company that had donated generously to marine research. Outfitted with schooners capable of ocean crossings, towing fine-mesh nets and catching hundreds of larvae, he was able to show that the farther from the European coast he went, the smaller the eel larvae became. After almost two decades of cruising the Atlantic, Schmidt was able to assert that both the American and European eels spawned somewhere in the southwestern part of the Atlantic—the Sargossa Sea. “No other instance is known among fishes of a species requiring a quarter of the circumference of the globe to complete its life history,” Schmidt wrote in 1923. “Larval migrations of such extent and duration…are altogether unique in the animal kingdom.”

Schmidt and his colleagues went on to search for the spawning areas of other freshwater eel species in the Indo-Pacific region, but with limited success. No other discoveries of anguillid eel-spawning areas came until 1991, when an expedition led by Katsumi Tsukamoto of the Ocean Research Institute in Tokyo found the spawning grounds of the Japanese eel. Japanese scientists had searched unsuccessfully for the spawning area of Anguilla japonica for six decades. But on this particular newmoon night in the Pacific Ocean, in the Philippine Sea to the west of Guam, Tsukamoto and the other scientists on board netted the smallest larvae of that species that had ever been collected and finally determined the location of the spawning area of the Japanese freshwater eel. Still, they had not captured any adults.

Mike Miller, then a graduate student from the University of Maine, Orono, who was on the fateful expedition, described what it was like to look for spawning eels in the open ocean. “You could be fifty meters away and not find anything,” he said. “It’s an issue of scale—the ocean is huge. To get where eels are spawning, it’s statistically very low probability. Almost impossible. You’d have to be very lucky.” It didn’t help that every previous year in which they’d made a cruise to look for the adults they’d run afoul of the elements. “I can’t remember a single eel cruise when there hasn’t been a typhoon that caused us to change course,” Miller added. It’s almost like Poseidon is trying to keep the eels’ secret.”

That’s the greatest beauty I find in eels: the idea of a creature whose very beginnings can elude humans, and the potential that idea holds for our imaginations.

Like the people I met in my travels, I get a good feeling from eels. The nights and early mornings I’ve spent with them during the fall migration have pulsed with energy and light. Standing in an eel fisherman’s river weir in the cool September dark, watching the vein-like ropes of fish fill his womb of wood and stone, I’ve come to believe the Maori yarns about encounters they’ve had with the water guardians.

We allow ourselves to believe that nature can be explained. In the process we confine nature to those explanations. The eels, through their simplicity of form, their preference for darkness, and their grace of movement in the opposite direction of every other fish, have helped me to see things for which there is no easy classification things that can’t be quantified or solved, and get to the essence of experience. They have been my way back.

Artist, writer, activist, and Yale graduate James Prosek made his authorial debut at nineteen years of age with Trout: an Illustrated History (Alfred A. Knopf, 1996), which featured seventy of his watercolor paintings of the trout of North America. Prosek has shown his paintings with the Gerald Peters Gallery, New York and Santa Fe; Meredith Long Gallery, Houston; as well as with Wajahat/Ingrao, New York, the d.u.m.b.o. arts center, Brooklyn, Reynolds Gallery, Richmond, VA and the Aldrich Contemporary Art Museum in Ridgefield, CT. He has upcoming shows at the National Academy of Sciences, DC, the Academy of Natural Sciences in Philadelphia, the Addison Gallery of American Art in Andover, MA and the New Britain Museum of American Art in New Britain, CT. Prosek has written for The New York Times and National Geographic Magazine and won a Peabody Award in 2003 for his documentary about traveling through England in the footsteps of Izaak Walton, the seventeenth-century author of The Compleat Angler. He co-founded a conservation initiative called World Trout in 2004 with Yvon Chouinard, the owner of Patagonia clothing company, which raises money for cold water habitat conservation through the sale of T-shirts featuring trout paintings. Prosek is a curatorial affiliate of the Peabody Museum of Natural History at Yale, and a member of the board of the Yale Institute for Biospheric Studies.

Eels have been a source of fascination to writer, artist and conservationist James Prosek since childhood. His introduction to the slimy, muscular fish occurred when fishing as a boy in the ponds and rivers of Connecticut. He would catch them by accident when fishing for something else. But when an old game warden explained that they were born thousands of miles away in the Sargasso Sea, somewhere in the Bermuda Triangle, Prosek became hooked and determined to learn as much he could about the mysterious creatures. Prosek’s journey takes him to Maine, where New England fishermen reap the benefits of a multibillion-dollar eel business; to Japan, where the fish are a staple of Japanese diet, with more than 130,000 tons of eel consumed each year; and to the Maori in New Zealand, where eels are revered, often depicted as mythical beings or guardians. Eels can be found all over the globe, in fresh and salt water ecosystems alike. But today, risk of over-fishing and the presence of dams and other obstacles that prevent eels from reaching their oceanic spawning grounds pose new threats to an animal that once roamed the planet alongside the dinosaurs.

The full film will be streaming on our website the day after broadcast.

Perhaps it’s because our furry friends have long provided us with comfort, camaraderie, and unconditional love. Cats and dogs are our unending source of kisses, cuddles, slobber, claws, and laughs. Watch as NATURE shares the stories of pet owners and their beloved animals. From a very special dog named Jerry, to a cat that saved a man’s life, Why We Love Cats and Dogs presents a portrait of some of the most powerful and remarkable connections we experience as humans—the unbreakable bonds with our pets.

Four-time Emmy Award winner, filmmaker and director Ellen Goosenberg Kent kept the 10-month production of NATURE’s Why We Love Cats and Dogs on the right track. Ellen brings a strong visual sense to the art of storytelling and was able to illuminate the dynamic human-pet relationship, revealing how dogs and cats share our emotions in many significant ways.

Update February 19, 2009: Professional dog trainer and behaviorist Sarah Wilson answers Five Good Questions on PBS Engage.

Online content for Why We Love Cats and Dogs was originally posted February 2009.

Photo by Joe Sinnot © EBC

Accidentally or intentionally released pythons and other exotic animals, such as parrots, reptiles, and lizards are inhabiting dry as well as wet habitats, and feeding on or competing with native species. Giant pythons are well-adapted for success in Florida, where the habitat is similar to their Asian home. Although they are non-venomous, pythons are among the largest snakes in the world, reaching up to twenty-six feet long. Their size and power makes them one of the top predators in Florida’s Everglades National Park, taking on even the alligators, and posing a threat to many of the indigenous and endangered species.

NATURE follows teams of scientists and hunters as they use their vast knowledge of snakes and their prey to uncover the impact of the pythons on the park’s fragile ecosystems. Herpetologist Shawn Heflick uses some innovative techniques to observe the mechanics of the snake’s bite, while scientists Stephen Secor and Skip Snow employ advanced technology to analyze the ways in which pythons swallow and digest animals that can be more than half their own body size. Watch as a wild python ingests an alligator whole.

Journey with NATURE as it investigates what comes next in the story of the Invasion of the Giant Pythons.

NATURE’s two-part special Dogs That Changed the World tells the epic story of the wolf’s evolution, how “man’s best friend” changed human society and how we in turn have radically transformed dogs.

From the tiniest Chihuahua to the powerful and massive English Mastiff, modern domesticated dogs come in a bewildering array of shapes and sizes, with an equally diverse range of temperaments and behaviors. And yet, according to genetics, all dogs evolved from the savage and wild wolf — in a transformation that occurred just 15,000 years ago.

In Part One, “The Rise of the Dog,” you’ll learn about how the domestication of dogs might have taken place, including the theory of biologist Raymond Coppinger that it was the animals themselves — and human trash — that inspired the transformation. The genetic analysis of Peter Savolainen of the Royal Institute of Technology in Sweden has placed the origins of domesticated dogs — and those of the first dog — in East Asia. You’ll also discover 14 dog breeds that controversial genetic studies show are the most ancient — and the best living representatives of the ancestors to all living dogs.

Preview Part Two: Dogs by Design

Over 400 breeds of dog are recognized around the world, each unique for its personality, habits, and form. Most of these breeds exploded onto the scene over the past 150 years, spurred by the Victorian-era passion for the “dog fancy” — the selective breeding of dogs to enhance particular characteristics. By tinkering with its genetics, humans made the dog the most varied animal species on the planet — and also created a host of hereditary health problems.

Despite the plethora of new shapes and sizes, dogs have retained the instincts bred into their ancestors by thousands of years of work: the urge to herd or hunt, to dig and to guard. In Part Two, “Dogs by Design,” you’ll discover how these hard-wired behaviors help different types of dogs, from hounds to herders, excel at different tasks (and why it can sometimes be so difficult to train them to do otherwise). You’ll also learn how dogs’ finely tuned senses are serving humans and saving lives. Buy the DVD. This film premiered April 2007.

Since the 2003 invasion of Iraq, news about the fate and future of this Middle Eastern country has been at the forefront of our national consciousness, making an impact on our daily lives, appearing in every newspaper and news program, the subject of endless numbers of personal and political discussions. But if you think you’ve heard every imaginable story about life within Iraqi borders, think again. There is at least one major element in this geopolitical drama that the American media has mostly overlooked, and it lies at the cross section of regional politics and the natural environment. NATURE’s Braving Iraq unravels this tale about what was once one of the richest and most important wetlands in the world – from its virtual destruction by a ruthless dictator to its exciting, new prospects for a miraculous recovery.

As recently as the 1980’s, Iraq’s Mesopotamian Marshes were reminiscent of the Garden of Eden – indeed, many biblical scholars believe they are one and the same. Fed by the combined waters of the Tigris and the Euphrates rivers, this enormous marshland of over 6,000 square miles dominated southern Iraq. For more than 7,000 years, these wetlands provided a bountiful home for both wildlife and humans. A large population of indigenous people, the Ma’dan Tribes known as Marsh Arabs, had thrived there for centuries. But in the 1990’s, due to political conflict, Saddam Hussein attempted to eradicate them – not through systematic extermination, but by destroying the marshes on which they depended for survival. Massive canals were dug, diverting river water away from the wetlands and towards the Persian Gulf. Huge embankments were built to prevent water from entering the marshes. What had been a green paradise twice the size of the Everglades shrank to less than 10% of its original size. Most of it was transformed into a parched, lifeless desert. The wildlife and the people were forced to leave.

But the story did not end there. Due to the imagination and the efforts of a coalition of individuals, restoration of the marshes has become more than a dream. Civil strife, serious security incidents and droughts make for slow progress, but various groups are chipping away at the embankments, trying to successfully flood the marshes once again. Azzam Alwash, an engineer raised on the banks of the Euphrates, left Iraq for America to escape from Saddam’s regime, but he has returned to undertake one of the largest habitat recreation projects in the world. Filmmakers David Johnson and Stephen Foote follow Azzam, chronicling his efforts to breathe new life into the green paradise he remembers from his childhood, while also navigating the inherent dangers of working in a dangerous and politically volatile region.

Is there any hope that such a massive ecosystem can be brought back to life? Have the exiled rare birds of the marsh, such as the marbled teal and the Basra reed warbler, survived? And will they return to their old territory? Success is uncertain, but some Iraqis feel that the fate of the country itself is tied to the fate of the marshes – and as small signs of hope for natural recovery begin to appear, Iraq’s political future seems to brighten as well.

Watch as a California town overrun with skunks deals with their furry problem, and see what life is like for an evolutionary biologist in New Mexico who runs one of the few sanctuaries for skunks. Meet a researcher on the sandy shores of Martha’s Vineyard who stalks her striped specimens at night, and a woman in Ohio who runs a shelter and adoption agency for abandoned pet skunks. Is That Skunk? paints a complete portrait of the misunderstood skunk family, Mephitidae, and the people who love them.

To order a copy of Is That Skunk? please visit the NATURE Shop.

Online content for Is That Skunk? was originally posted January 2009.

Photo credit: Cici Clark / © WNET.ORG

Swaziland resident Clifton Koen doesn’t really care for snakes, but his wife, Thea Litschka-Koen, is crazy about them. With her husband’s sometimes reluctant help, she has endeavored to change attitudes about black mambas and other snakes found in the area. In addition to starting the nation’s only reptile park, devoted to educating the public and providing a refuge for the animals, the two have become the region’s go-to experts for safe, humane snake removal from homes, schools, resorts and workplaces. In the course of catching and relocating any number of snakes per day, Thea and Clifton give impromptu lessons about the snakes, covering fact and fiction, and do their best to prevent any unnecessary casualties – human or reptile.

In addition to their other efforts, Thea and Clifton developed a program designed to track black mambas in the wild for the first time and to gain new insights into their behavior. With the help of a snake expert from Johannesburg, they were able to surgically insert radio transmitters in a number of captured black mambas, allowing them to follow the snakes after their release. If their research pays off, they may be able to show that their relocations are working, successfully removing snakes from residential areas for the long term, and thereby bringing some relief to the locals and some respite for the snakes.

Black Mamba premiered October 3, 2010.

Photo by Andrew Yarme © Tigress Productions

Hand-rearing the brothers, teaching them the life skills cheetahs need to survive, and observing the cubs as they pass through key stages of their development, Simon’s efforts to rehabilitate the cheetahs and reintroduce them to the world of wild cheetahs is filled with delight but also sadness. Simon becomes more deeply attached to the orphans, making difficult, yet critical decisions that determine their fate. When tragedy strikes, Simon is overcome with emotion, but has to make clear decisions for the welfare of Toki. Buy the DVD. This film premiered November 2007.