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Wednesday, Oct. 5, 2005 08:27 am

Earth Talk

From the editors of E/The Environmental Magazine

Dear “Earth Talk”: What are the ramifications for wildlife of cross-breeding species and creating animals such as the “zorse” (horse/zebra mix) and the “beefalo” (cow/buffalo)? — Kiernan Warble, San Francisco, Calif.
In 1986, a 14-foot-long male false killer whale and a 6-foot-long female Atlantic bottlenose dolphin at Honolulu’s Sea Life Park Hawaii became the proud parents of Kekaimalu, the first “wholphin” ever born in captivity. In the 19 years since, Kekaimalu, with a little help from male bottlenose dolphins, has given birth to three wholphins herself, each one three-quarters dolphin and one-quarter whale. Though rare, the interbreeding of different animal species does occur in nature, even when unaided by humans. But mankind, in search of marketable traits or the next big zoo attraction, has long turned to controlled cross-breeding. The mule (horse/donkey mix) has been a beast of burden for centuries. The zorse, also bred for its work endurance, has been around since the late 1800s. Beefalo was introduced in the 1960s to increasingly health-conscious American consumers to provide a heart-healthier alternative to pure beef. And the Sierra Safari Zoo in Reno, Nev., now entertains visitors with a 1,200-pound “liger” hybrid. The liger has the face and mane of his father, an African lion, and the body and striping of his mother, a Bengal tiger. Says the zoo’s Web site, “He roars like a lion and swims like a tiger. He’s definitely all cat.”
But according to Science World magazine, such a pairing would probably not occur in the real world: “If these ferocious cats met in the jungle, a tiger would probably not choose to visit a pride of lions; a raucous brawl — not romance — would be the more likely result. But with little choice in captivity — like an open zoo — the odd coupling may occur.” Indeed, animals seldom interbreed in the wild, for one very important reason: Unlike the wholphins at Hawaii’s Sea Life Park, offspring are usually, like mules, unable to reproduce. Hybrid species would likely have many other survival challenges as well, even those, such as beefalo, that can reproduce. Nature has evolved unique traits within individual species enabling them to adapt to their unique climates, fight off particular predators and diseases, and live off the indigenous food supply. These traits are passed on from generation to generation among naturally occurring animals but may not do so in hybrid creations. Genetically engineered animals also pose several potential ecological threats, chief among them the decrease in genetic diversity that has been the hallmark of evolution’s march. One negative outcome of too much genetic tampering could be greater vulnerability of both animals and humans to new strains of infectious diseases. Biotech animal hybrids can also wreak havoc on native wildlife. A study conducted at Purdue University concluded that if 60 genetically engineered salmon escaped into a native natural population of 60,000, it would take only 40 generations for the wild salmon to be completely wiped out.
“Species are adapted to specific conditions,” adds Susan Haig, who has conducted hundreds of studies on wildlife hybridization in her role as a wildlife ecologist with the U.S. Geological Survey. “So I think it’s important to maintain the integrity of species.”  
For more information: Sea Life Park Hawaii, www.sealifeparkhawaii.com; Sierra Safari Zoo, www.sierrasafarizoo.com; U.S. Geological Survey’s Haig Lab, fresc.usgs.gov/staff/haig.
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