Dear EarthTalk: What are the ramifications for wildlife of cross breeding species and creating animals like the "zorse" (horse and zebra mix) and the "beefalo" (cow and buffalo)?
—Kiernan Warble, San Francisco, 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.
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."
Dear EarthTalk: What are "Toad Tunnels?"
—Peter Sterling, Worcester, VT
A group of conservation-minded Cornell University students invented "toad tunnels" in 2003 to help amphibians better negotiate a series of risky road crossings to springtime breeding ponds in a nature reserve in upstate New York"s Cornell Plantations. The students knew that frog populations were already in steep decline around the world for a variety of reasons, and they wanted to help.
When the students discovered that hundreds of toads, salamanders, newts and turtles were dying on one particular road through the area each spring evening, they hatched a plan. Working with a local polymer company, they designed and installed a "drift fence" to help guide the critters to previously existing culverts underneath the road. The fences—dubbed "toad tunnels" by the students—even curved over on top to prevent hopping creatures from turning back and abandoning their important reproductive missions. After a prototype test saved hundreds of amphibians one night at a particularly difficult road crossing, the students raised $5,000 to install toad tunnels at other key spots around the Cornell campus and beyond.
Cornell"s toad tunnels are just one example of hundreds of innovative structures designed to help wildlife make safe passage around, under or over various kinds of man-made barriers. In Amherst, Massachusetts, similar tunnels help salamanders reach breeding pools each spring—and a "Watch Out for Salamanders" sign alerts drivers to slow down in sensitive areas. And in Utah, fences channel deer across busy state highways around Park City, with white stripes on the roads serving as visual cues for the animals and to alert drivers. Researchers estimate that road kill in the region has dropped by 40 percent as a result.
Sadly, roadways kill hundreds of millions of animals every year. With highways already covering more than two percent of the land in the contiguous 48 states expanding and increasing, wildlife populations stand little chance of surviving the onslaught of automobiles into their habitat.
From the 1950s through the 1970s, the Human Society of the United States sampled road kill data from across the country and estimated that one million vertebrate animals—mammals, birds, reptiles and amphibians—were getting mortally familiar with the wrong end of a car bumper on U.S. roads every single day. But according to surveys conducted over the most recent decade, American motorists are only killing 500,000 vertebrate animals per day.
But Mark Braunstein of the non-profit Animal Protection Institute isn’t sure if that trend means we’ve made progress or if animal species have simply gotten scarcer. Still, others remain optimistic that so-called "wildlife mitigation" efforts undertaken in recent years have been paying off. In the old days, the construction of interstate highways took precedence over environmental concerns. But that notion may be falling by the wayside, as Congress last year allocated a record $3 billion to fund toad tunnels and other ambitious wildlife redirection efforts across the country.