More about our very endangered golden froggy friends.
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Hopping to it to preserve the rare mountain yellow-legged frog
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Hopping to it to preserve the rare mountain yellow-legged frog
Researchers' efforts to increase the California amphibian's numbers include
replicating hibernation.
By Louis Sahagun
March 5, 2010 | 6:26 a.m.
Some like it hot. Apparently, the endangered mountain
yellow-legged frog is not among them. The 3-inch-long amphibians much prefer it cold as melting
snow. So conservationists at the San Diego Zoo have placed two dozen of the
nearly extinct frogs in refrigerators they joshingly refer to as
"Valentine's Day retreats" in hopes the amphibians will emerge with
the urge. To mate, that is. The big chill at the zoo's Institute for Conservation Research
represents one of the most ambitious wildlife reintroduction experiments in the
nation. If it is successful, the frogs could produce upward of 6,000 tadpoles
next month -- all of them scheduled for a spring homecoming in a remote San
Jacinto Mountains stream from which they have been absent for a decade. Scientists hope many of those tadpoles will mature and
produce new generations in the wild, paving the way for the Rana muscosa
population to reestablish residency in Southern California
and grow exponentially.
"Will it work? We think so," said Jeffrey Lemm, a
zoo research coordinator. "A month from now, there could be tubs of
tadpoles all over the place. Eventually, we may have thousands of adult frogs
in self-sustaining populations for the first time in half a century." Mountain yellow-legged frogs thrived for thousands of years
in hundreds of streams cascading down the San Gabriel ,
San Bernardino and San
Jacinto mountains. Since the 1960s, the species has been decimated
by an array of threats: fires, mudslides, pesticides, fungal infections, loss
of habitat as a result of development, and the appetites of nonnative trout,
bullfrogs and crayfish. Today, fewer than 200 of their descendants are believed to
exist in nine isolated wild populations, including a group in the San Gabriel Mountains' Devils Canyon that survived last year's devastating Station fire. Their minuscule, scattered population gives mountain
yellow-legged frogs the distinction of being one of the most endangered
amphibians on the planet. The most intimate details of their mating behavior
are the focus of a master's thesis project being conducted at the institute by
research technician Frank Santana.
In their native habitat, the frogs flock to streams gushing
with spring snowmelt. Males announce their availability for amphibian amour
with a low-pitched underwater bark. Parental discretion is advised for what follows: "A
male gets a good grip of a female with his forearms, and the female, if she's
in the mood, let's him," Santana said. "Then the male thrusts his
whole body to stimulate the release of her eggs. The female goes into
contractions as both arch their backs to line up their cloacae." Sperm and eggs are released simultaneously. Tadpoles emerge
from the eggs about three weeks later. In the wild, only 3% to 5% mature into
adult frogs. "In the laboratory, the hard work comes when we've got
a bazillion 2-millimeter-long tadpoles on our hands in need of daily water
changes, and meals of frozen lettuce and fish food," Santana said.
The zoo's recovery program was launched in the summer of
2006, with 82 tadpoles rescued from a drying creek in the San Bernardino National
Forest . Two years later, institute researchers discovered a clutch
of 200 eggs in one of their tanks. However, the frogs were younger than is
typical for breeding and only a handful of the eggs were fertile. The institute
became the first to breed a yellow-legged frog in captivity when one of those
eggs produced a tadpole that matured into a still-surviving adult. Now the institute has 61 frogs, including the 16 females in
the refrigerator -- each one of them, Lemm said, "looking nice and healthy
and bulging with 200 to 300 eggs." All the tadpoles produced in the laboratory will be
reintroduced into a mountain stream that U.S. Geological Survey biologists have
determined is free of predators.
The recovery effort has been funded by the California
Department of Transportation to mitigate for emergency work to stabilize a
slope near the frog's habitat on California
330 in the San Bernardino Mountains . It is
part of an ongoing collaborative effort of government and nonprofit partners to
increase the number of frogs in native habitat and in captive breeding
programs. The Fresno Chaffee Zoo recently received about 100 tadpoles
rescued last summer from the Station fire area. The Los Angeles Zoo and the Living Desert
in Palm Desert will each get 10 adult frogs for
captive breeding purposes. In the meantime, federal wildlife authorities are developing
measures to reduce the effect of human activities in areas where the
yellow-legged frog is still found and may be reintroduced. That includes a
remote stretch of Tahquitz Creek in the San Jacinto Wilderness near Idyllwild,
where two yellow-legged frogs were discovered last year.
"A few years ago, there wasn't even a captive breeding
program for these frogs," Santana said. "Now, we are hoping to
reestablish populations by mimicking their natural cycles. For these frogs,
that means winter hibernation, spring thaw and lots of tadpoles.
Hopefully."