SPECIES OF DOLPHINS
Northern right whale dolphin There are 37 different kinds of dolphin. The most familiar one to humans is the bottlenose dolphin like Flipper and most of the dolphins in dolphin shows. The most numerous are the common dolphin, which have distinctive white and black markings. There are millions of them. They have been observed gathering in large groups and going into a frenzy, perhaps to panic schooling fish.
Bottlenose dolphins are usually gray in color and have a pronounced bottle-shaped snout. Often featured in television shows and movies, they can reach lengths of nine feet and weigh as much as 600 pounds. They eat around 30 pounds of fish a day, mostly pinfish, pigfish and mullet, and come to the surface an average of once every 28 seconds to breath.
Spinner dolphins are smaller than bottlenose dolphins and are named are their spinning leaps. They are about 1.5 meters long and weigh around 65 kilograms. They have three shadings: dark gray on their back and on their dorsal fin; blue-grey in the middle and white on their bellies. They have sharper snouts than bottlenose dolphin and slimmer bodies. Long-snouted spinner dolphins are known for their acrobatic skills. Found in tropical waters, they can jump 10 feet in the air and have been observed spinning seven times in a single leap.
Humpback dolphin The Atlantic Humpbacked dolphin is common in coastal waters off West Africa. It is known for cooperating with fisherman to drive fish towards their nets. Atlantic white-side dolphins are often seen off the coast of the United States, sometimes riding the bow waves of humpback and fin whales. Northern right whale dolphins do not have a dorsal fin. They live in the north Pacific and have been observed leaping 23 feet in the air.
Spotted dolphins are regularly approached by humans in the Bahamas. Their populations in the Pacific have been devastated by tuna fishing. Their spots develop with age. Dusky dolphins are found mostly around New Zealand. They are acrobatic, curious and easy to approach. Swimming with these dolphins has became a major tourist attraction.
In July 2005, the discovery of a new species of dolphin was announced. The Australia snubfin dolphin lives in northern, coastal Australia. It is related to the Irrawaddy dolphin---a river dolphin---but different enough to be declare a new species.
Freshwater Dolphins in China
The baiji, a freshwater dolphin species, is the rarest and most endangered of all whale, porpoise of dolphin species. It lives on a 1,000-mile stretch of the Yangtze river between the mouth of the river and the Three Gorges. They have traditionally been viewed by some as "the Goddess of Chang Jiang" and are a good omen to any fisherman who spots one.
Baijis, also known as white flag dolphins or Yangtze river dolphins, weigh between 300 and 500 pounds and reach a length of 8.5 feet. They have a long snout and small eyes and have white sides and a pale blue grayish back. They feed primarily on fish, which they locate with sonar since they are nearly blind.
Baijis can live to be 25 to 30 years of age. They stay under water for an average of 20 seconds and can dive for up to two minutes. They are usually found in pairs or social units of 10 or so members. Some scientists regard them as a subspecies of Irrawaddy fresh water dolphin.
There are four generally recognized species of freshwater dolphin. The Irrawaddy fresh water dolphin is found in the Mekong River in Laos and Cambodia, the Mahakam River in Kalimantan in Indonesia, and the Yangtze in China. They were once found in the Chao Praya River, which flows through Bangkok, but haven't been seen there in decades (See Laos). The three other live in the Ganges in India, the Indus in Pakistan and the Amazon in South America.
For millions of years river dolphins have inhabited the Yangtze. The first are believed to have migrated up the Yangtze 20 million years ago.
River Dolphin Sonar
River dolphins are nearly blind. They have very small eyes. Indus and Ganges dolphins even lack lenses and can do little more than distinguish light and dark and night and day. The water they swim in is often so muddy that even if the could see they could only see a few inches in front of them.
In the sea, dolphins use their echolocation primarily to locate and catch fish. River dolphins use it primarily to navigate through the murky water so they can sweep for fish. They swim on their sides and sweep their long bony snouts in wide arcs across the river bottom, emitting long trains of echolocation clicks that let them hunt fish in all but opaque waters."
See Dolphin Echolocation, Sea
Endangered Freshwater Dolphins in China
As of the 1990s only 100 or so baijis remained in the wild. Their number had declined from 6,000 in the 1950s to 400 in the 1980s to 150 in 1993 to 100 in 1995. At that point their future didn't look good: they live in one of the world's most densely populated areas and had a large part of their natural habitat gobbled up by the Three Gorges Dam project. Experts estimated that species would probably be extinct within 10 to 15 years.
A survey of baiji in 1997 found 13 of them. A four boat survey in 1999 counted four. A pair was seen in Hongpu Lake in July 2005. A sighting was recorded in the summer of 2006. The last one captivity died in 2002.
The baiji is now regarded as "functionally" extinct. A five-week survey in 2006 conducted by 30 scientists over 1,700 kilometers of the Yangtze, using sophisticated viewing equipment and ultra-sensitive microphones failed to locate a single one. August Pfluger, a Swiss researcher and leader of the survey told the Washington Post, "It is possible that there are two or three that we missed somehow but functionally they are extinct. It is finished. This is very, very, sad."If they are extinct they are first species of whale dolphin, or porpoise to be made extinct by man.
A Chinese man videotaped a baiji swimming in the Yangtze River in the summer of 2007. The man was quoted Reuters as saying, "I never saw such a bg thing in the water before so filmed it." He said he was about one kilometer away and it jumped several times.
Baiji have mainly been done in the last two or three decades by sewage and pollution dumped into the Yangtze and noise created by ship propellers which disrupt their sonar-based sensory system, making it difficult for them to find food and navigate through the river's murky waters. They have also been trapped in nets, hurt by boats dragging the river bottom and injured by motor boats. The fish they feed have been overfished with large nets. Many baiji have been snagged on rolling hooks, illegal fishing devices consisting of braided lines with a hundred or more hooks hanging off them.
Efforts to Save Freshwater Dolphins in China
An effort is being made to set up a sanctuary for the dolphins in a 13-mile-long oxbow lake, 150 miles upriver from Wuhan. For several months a year, the lake floods and is replenished with fish from the Yangtze River. So far this effort has been less than successful. The first dolphin placed in the sanctuary died after it got tangled in a net that separated the reserve from the river. After this construction began on a concrete barrier that didn't endanger the dolphins but allowed water and fish to flow in.
The leader of the save-the-baiji movement is Wang Ding, the director of river dolphin research at China's Institute of Hydrobiology and leader of the Wuhan Baiji Conversation Foundation. To save the dolphins and make the public aware of their plight, statues of the animals have been erected and a local brewery even introduced Baijitun beer.
There is also a species of river porpoise: the finless porpoise. In 1993 2,700 lived in the Yangtze. Less than 1,000 live there now according to an expedition in 2006. So they don't go the same way as the baiji and colony of 30 of them has been established in nature preserve, far from the polluted river. The hope is that they will reproduce.
Divisions over how best to conserve rare animals partly contributed to the demise of the baiji because foreign and Chinese zoologists were unable to agree on whether it should be taken to a reserve or looked after better in its natural environment. Reserves were set up for the baiji and laws and regulations were enacted to help them. But these reserves existed largely in name only and the laws were not enforced.
Vaquita, the World's Smallest Porpoise: Only Around 200 Left
Vaquita Vaquita are the world’s smallest porpoise. There are only around 200 of them left and they all live in the northern reaches of the Gulf of California, Mexico. The gulf, also called the Sea of Cortez, is the thousand-mile-long spear of ocean wedged between the mainland of northwestern Mexico and Baja California. The population of the species is falling at an alarming rate mainly because of accidental entanglement in fishing gear. The animal’s slow maturation and low birthrate compound the problem. [Source: Robert L. Pitman and Lorenzo Rojas-Bracho, Natural History magazine, July -August 2007]
The vaquita was first recognized as a new species in 1958, on the basis of three skulls found on beaches in the northern gulf. But a quarter century passed before a live animal was scientifically documented, and only in 1985 were its external features first described by biologists.
Robert L. Pitman and Lorenzo Rojas-Bracho wrote in Natural History magazine, “Its torpedo-shaped body measures less than five feet from snout to tail; calves are just twenty-eight inches long at birth, the size of a large loaf of bread. From a distance, the vaquita appears drab gray with a lighter belly, but at close range some intriguing details in the paint job emerge. A black stripe runs forward from each flipper to the middle of the lower lip, so the animal appears to be holding its own bridle. It has a black, circular patch around each eye. And its black lips set off a haunting little smile: Mona Lisa with black lipstick.
But the vaquita has no reason to smile. The world population of vaquitas is probably about 200 individuals---you can see more people in a Wal-Mart on a busy weekend. And though Wal-Martians are definitely in no danger of extinction, the vaquita is losing market share. Gill nets---nearly invisible fishing nets set in the water like curtains and often left unattended---are the single greatest cause of vaquita mortality each year. Vaquitas become entangled and drown when they swim into the nets by accident; or they might be lured there by fish that are already stuck. Vaquitas aren’t the intended targets of any fishery; they’re merely the bycatch of local fishermen trying to earn a living---collateral damage.
Vaquita size With the vaquita’s population in steady decline, its distribution in the northern gulf has also contracted, so that its range is now the smallest of any marine mammal. Nearly the entire population lives in a region less than forty miles across. To put that into perspective, while on surveys throughout the gulf, we have seen a few dozen vaquitas over the years. But never have we seen one without being able to look up and see Consag Rock, a 300-foot-tall, guano-covered spire in the middle of the northern gulf.
Even the vaquita’s scientific name, Phocoena sinus, acknowledges its claustrophobic range. Phocoena is derived from both the Greek and Latin words for “porpoise”; sinus is Latin for “bay” or “pocket,” and refers to the animal’s restricted home waters. (The common name, vaquita, means “little cow” in Spanish---a rather fitting name now that biologists know that all cetaceans are the product of a successful re-invasion of the ocean by terrestrial ungulates.)
Beyond those population estimates, and despite numerous surveys to observe vaquitas in the wild, little is known about their biology or life history. Because the animal is shy as well as rare, it has not readily disclosed its secrets. But what little is known does not bode well for its future. The normal lifespan is probably twenty years or more. It reaches sexual maturity between three and six years of age, and females apparently give birth to a single calf every other year. It typically travels alone or in mother-and-calf pairs. A recent study determined that the species has little or no genetic diversity; it may have passed through a population bottleneck at some time in its past, or evolved from a small founder population. The combination of low numbers, late maturity, low birth rate, and low genetic diversity makes the vaquita vulnerable to extinction, even without such strong pressure from people.
Vaquita range Robert L. Pitman and Lorenzo Rojas-Bracho wrote in Natural History magazine: Fishermen, armed with nets, are the main reason for the vaquita’s decline---just as they are for the mortality of marine mammals everywhere else in the world. At a recent forum convened in San Diego to address the fate of the vanishing vaquita, the organizers displayed a gallery of nearly every known photograph of the species. Most showed a dead animal swaddled in gill net in the bottom of a fishing boat, that innocent smile frozen on its face in death as in life. There were only a couple of photographs of live animals, and they were no more than blurred images of a head or a dorsal fin hastily rolling out of sight in the distance. We were struck that a large mammal living in our time could be driven off the planet forever, and leave behind such a scant record that it was ever here.
The best estimate of the world’s vaquita population to date comes from a 1997 shipboard survey of the vaquita’s known range, which was conducted by the U.S. National Marine Fisheries Service in collaboration with Mexican investigators. From the survey data, Armando Jaramillo-Legorreta, a Ph.D. candidate in oceanography at the Autonomous University of Baja California in Ensenada, and several of his colleagues estimated the vaquita population at 567 individuals.
To determine whether the population is growing, declining, or holding steady, one must know, among other things, its mortality from both natural and human causes. The latter is essentially the number of animals that die in nets every year, and that critical piece of information was supplied by Caterina D’Agrosa, now a postdoctoral fellow at Arizona State University in Tempe. Between January 1993 and January 1995, as part of her master’s thesis, D’Agrosa had interviewed fishermen and placed observers aboard fishing boats, primarily in El Golfo de Santa Clara, one of the three main fishing communities in the northern gulf. Extrapolating from her sample, she estimated that seventy-eight vaquitas were being killed annually, an overall population decline of about 10 percent per year. At that rate, a population of 567 individuals in 1997 would have plummeted to about 200 by now.
Efforts to Save the Vaquita
Hector's dolphin In 1993, as a result of public and scientific outcry about its fate, the Mexican government created the Upper Gulf of California and Colorado River Delta Biosphere Reserve [see map]. Within the reserve, gill nets are prohibited. At the time, the reserve was thought to include most of the vaquita’s marine habitat, but after two shipboard surveys, in 1993 and 1997, it became clear that as much as half of the population was actually living south of the reserve boundary. Consequently, in December 2005 the Mexican government designated a vaquita refuge, which overlaps part of the biosphere reserve and includes an area where some 80 percent of recent vaquita sightings have been made.
In spite of the good intentions reflected by the creation of those protected areas, harmful fishing practices have continued virtually unchecked. A 2006 review concluded that there has been little or no change either inside or outside the biosphere reserve since its creation. When we visited the vaquita refuge in March 2006, we found unattended gill nets set right in the middle of it. One of us (Rojas-Bracho) recently launched a series of aerial surveys, which will provide a far better appraisal of fishing activity throughout the region than has so far been possible. But because the boundaries of the reserve and the refuge are not marked, and because there is little enforcement of the no-gill-netting rule, poor results seem all but inevitable.
Vaquita conservation, of course, raises thorny ethical and sociological issues. The people who live along the desert shores eke out a tenuous living by fishing in the same waters as the vaquita. They simply want to keep their families fed and improve their lot. The tragedy is that their poverty and their struggles will continue long after the last vaquita loses its own final struggle in a ball of monofilament net.
It is all too easy to imagine the end of the vaquita: An exasperated fisherman wrestles with an entangled carcass under the blazing Mexican sun. He finally extricates it from the net and dumps it unceremoniously over the side of his panga---his small, open fishing boat. As the last vaquita sinks out of sight, the last human being ever to see one goes back to pulling his net. We need to take care of this fisherman if we want to take care of the vaquita.
Baiji and Vaquita
Fraser's dolphin And then there’s the baiji (Lipotes vexillifer), a dolphin that lived only in the Yangtze River. In the fall of 2006 one of us (Pitman) took part in a search for the last baiji. For the past twenty to thirty years the baiji had been recognized as the world’s most critically endangered cetacean, because of its high rate of accidental drownings in fishing gear. In a six-week survey, the searchers failed to find a single individual---and in the end, were forced to conclude that the baiji, after more than 20 million years swimming in the Yangtze, was probably extinct.
There are troubling similarities between the baiji and the vaquita, the next cetacean in line for extinction. Historically, both species occupied small, insular ranges surrounded by fishing communities. They both faced the same threat to survival: nets. Both species, like all cetaceans, were slow to mature and had long intervals between births, so even if the threats to their survival had been removed, their reduced populations would have recovered very slowly. Both had been at risk of extinction for some time. “Protective measures” were put in place for both: reserves were created and laws were crafted that made harmful fishing practices illegal in protected areas. But the reserves existed largely in name only, and enforcement was unsuccessful.
All that remains of the baiji are lessons. Extinction is real. Unmanaged fishing practices have the potential not just to reduce populations of aquatic mammals, but to catch and kill every last member of a species. And extinction can happen quickly, right before our eyes. A scientific paper published a few months before the Yangtze River survey concluded that the baiji would be extinct in twenty years if protective measures were not stepped up. But the last baiji had probably already died before that article was written.
How Can the Vaquita Be Saved
False killer whale As in the baiji’s case, the future of the vaquita is no longer a scientific issue. The time for surveys is over. The trend is clear, the threats are known, and the answer is simple: the nets must come out of the water. A recent socioeconomic survey of the northern gulf suggested that for about $25 million, all vaquita bycatch could be eliminated. The money would be directed toward the 3,000 or so fishermen who make their living putting nets into those waters, either to buy out their fishing gear and help them get into another line of work, or to teach them sustainable fishing practices that don’t threaten the vaquita. Economists from the U.S. and Mexico are now working to design such a program, but the money remains a stumbling block.
Maybe what the vaquita needs is a corporate sponsor. For the price of a couple of minutes of ad time during the Super Bowl, an underwriter could buy a future for the species...If this little porpoise goes extinct, many people will shrug off its passing as the disappearance of an obscure species from an out-of-the-way corner of the globe: “So what?” For others, however, the loss of any biological diversity on our planet is of grievous concern, particularly when what is lost is a relatively large, warm-blooded creature like the vaquita.
The vaquita has no value as a commodity: It is too shy and small ever to support an ecotourism venture. It is not a vital link in the marine food chain. There is no cure for any human disease lurking in its liver proteins. It is just a lowly beast trying to make its way, like the rest of us. Its loss would barely be noticed.
Yet it was part of the magnificent diversity of life on Earth that our generation inherited, and it is rapidly becoming part of the dwindling legacy we are leaving behind. We have a year or two now to decide whether we are going to let this species live, or whether, like the baiji, we vote it off the island and wipe that little black smile off the face of the Earth forever.
Image Sources: 1) Wikimedia Commons2) NOAA 3) Mikurashima tourism ; 5) China Science Academy; 6) Environmental News
Text Sources: Mostly National Geographic articles. Also the New York Times, Washington Post, Los Angeles Times, Smithsonian magazine, Natural History magazine, Discover magazine, Times of London, The New Yorker, Time, Newsweek, Reuters, AP, AFP, Lonely Planet Guides, Compton’s Encyclopedia and various books and other publications.
© 2009 Jeffrey Hays
Last updated March 2011