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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, 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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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.
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