Is Cross Breeding Wildlife Species Really A Good Idea? Not everyone agrees that playing God is worth the risks

Dear EarthTalk: What are the ramifications for wildlife of cross breeding species and creating “hybrid” animals like the “zorse” (horse and zebra mix) and the “beefalo” (cow and buffalo)?

—Paul Howe, Mill Valley, CA

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.

cross-breeding zorse
Some biologists fear that cross-breeding different animal species could have devastating effects on multiple species and the environment. Credit: Theo Stikkelman, FlickrCC.

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, Nevada, now entertains visitors with a 1,200-pound “liger” hybrid. It 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 website, “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 wolphins 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, like beefalo, that can reproduce. Nature has evolved a number of unique traits within individual species enabling them to adapt to their unique climates, fight off particular predators and diseases, and live off of their 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 a number of 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 by 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.”

CONTACTS: Sea Life Park Hawaii,; Sierra Safari Zoo,; U.S. Geological Survey’s Haig Lab,