Mythic Salamander Faces Crucial Test: Survival in the Wild
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Version 0 of 1. MEXICO CITY — Aztec legend has it that the first axolotl, the feathery-gilled salamander that once swarmed through the ancient lakes of this city, was a god who changed form to elude sacrifice. But what remains of its habitat today — a polluted network of canals choked with hungry fish imported from another continent — may prove to be an inescapable threat. “They are about to go extinct,” said Sandra Balderas Arias, a biologist at the National Autonomous University of Mexico working to conserve axolotls in the wild. The loss of this salamander in its habitat would extinguish one of the few natural links Mexicans still have with the city that the Aztecs built on islands in a network of vast mountain lakes. Its extinction in the wild could also erase clues for scientists studying its mystifying traits. Despite their precarious future in freshwater, axolotls (pronounced axo-LO-tuhls) have long flourished in aquariums. They have been bred successfully behind glass over the past century, raised as exotic pets or as laboratory specimens for scientists investigating their extraordinary ability to regrow a severed limb or tail. The Mexican axolotl is an odd-looking salamander with a flat head and spiked feet, unusual because it often spends its entire life in the so-called larval stage, like a tadpole, without ever moving to land. “It grows and grows in the same shape, and has the capacity to reproduce,” said the biologist Armando Tovar Garza. “We don’t really know why it doesn’t change.” Its gaze seems to captivate as its gills slowly beat. In Julio Cortázar’s short story “Axolotl,” the narrator is transfixed — “I stayed watching them for an hour and left, unable to think of anything else” — and experiences his own metamorphosis. The Aztecs and their descendants consumed axolotls as part of their diet, and the amphibians are still stirred into a syrup as a folk remedy for respiratory ailments. But in their only home, the canals of Xochimilco in the far south of the city, the axolotls’ decline has been precipitous. For every 60 of them counted in 1998, researchers could find only one a decade later, according to Luis Zambrano, another biologist at the National Autonomous University of Mexico. Gliding on a flat-bottomed boat through the canals where the Aztecs once farmed floating gardens, but where cinder block houses now dump their waste and students toss their beer cans during parties, Mr. Tovar described the threats. “The axolotl is suffering on two fronts,” he said, as pounding music and the smell of sewage filled the air. “One is the water quality. It’s not improving.” Then, as dimples appeared on the still surface of the canal, like raindrops before a deluge, another researcher leaned over and the axolotl’s second challenge became evident. “See how the water is moving? All of those circles?” asked the researcher, Leonardo Sastre Baez, who monitors fishing. “Those are the tilapias.” That resilient fish was introduced over 20 years ago, along with carp, in an effort to support Xochimilco’s fishermen. “The government thought, ‘If people can’t work, at least they can eat,’ ” Mr. Sastre said. But the tilapias reproduce faster than they can be caught, and they feed voraciously on the plants where the axolotls lay their eggs. Mexicans’ taste for axolotls has endured, generating some strong reactions from Europeans over the years. The naturalist and explorer Alexander von Humboldt wrote in the 19th century that the Mexicans he observed lived “in great want, compelled to feed on roots of aquatic plants, insects and a problematical reptile called axolotl.” Others would disagree with the interpretation. “Have you ever eaten frogs?” asked Roberto Altamirano, president of the fishermen’s association, who ate axolotls as a child and is now working to save them. “Well, that’s what it tastes like. Somewhere between fish and chicken.” The dire conditions in Xochimilco have generated debate among biologists. Some are adamant that the axolotl should be preserved only in its environment, but others are convinced it can survive only if new populations are introduced elsewhere. “It’s not about just rescuing the axolotl, it’s about rescuing the whole system of Xochimilco,” Dr. Zambrano said. Axolotls were once at the top of the food chain — eating insects, worms, crustaceans and even small fish — and their continued survival in the canals is a sign that the ecosystem of Xochimilco can endure as well. Finding them a new home would be tantamount to giving up, Dr. Zambrano argued. “That’s like saying, ‘to rescue polar bears, we’re going to have them in zoos,’ ” he said. “Or, ‘let’s build them a really cold refuge in the Amazon.’ ” Dr. Zambrano’s solution is two-pronged. First, he is promoting traditional methods of agriculture because he believes that Aztec practices provide an alternative to the polluting pesticides and fertilizers that many farmers in Xochimilco have adopted. He has found a few farmers willing to help his work, and in a twist, his team is grinding up tilapia to make organic fertilizer. He is also creating a series of small tilapia-free sanctuaries by blocking off the entrances to certain canals. After placing trackers on test axolotls, the team was surprised to see how lively they were in the wild. “In the lab, they become really still, and here they are very active,” Mr. Tovar said. “They’re more awake.” The axolotls have also been growing faster in the sequestered canals. Another team of researchers has begun testing for a new home far from the multiplying troubles of Xochimilco, in an artificial lake in Tecámac, about an hour outside Mexico City. “We could see that putting axolotls in there would be like sending them to the slaughterhouse,” said Ms. Balderas, the biologist, referring to Xochimilco. “If we look somewhere else, we might be able to give them a better life, like the one they had before.” Ms. Balderas and her student assistant, Marlen Montes Ruiz, are monitoring laboratory-bred axolotls to see if they are capable of hunting water bugs and other prey and coping in the wild after being pandered to for so long. So far, they say, axolotls have adapted well and have even become adept at hiding from the researchers, just as the ancient god eluded his captors. It can take hours to fish out all of the axolotls on measuring day. As Ms. Montes lowered a female axolotl back into the test pond, it began to undulate its tail. Her fingers loosened around its torso and the creature slipped under the water, through a green spot of sun, and then blended into dark brown. “There are a lot of water bugs; it’ll be O.K.,” she said. “They really do get lost here.” |