By Matthew
Berger, 7/25/12, The Daily Sentinel, Grand Junction, Colorado,
Although the
exact details won’t be known until months or years from now, the drought that
is drying up ponds and streams throughout Colorado and across the country
appears to be affecting wildlife in significant and diverse ways. Those animals
that rely on aquatic habitats may be hardest hit—not only fish but their
amphibious neighbors, the frogs and salamanders that call western Colorado
home.
In summers
like this, it may be hard to imagine the hot, dry Grand Valley as home to many
amphibians—and it seems it might be home to slightly fewer, for a while at
least, in the wake of this record-setting drought.
From the
chorus frogs and boreal toads found on Grand Mesa to the tiger salamanders that
wash down from there, the red-spotted toads along Colorado National Monument to
the canyon tree frogs tucked up in the monument’s canyons, the spadefoot toads
in their burrows out by Grand Junction Regional Airport to the Woodhouse’s
toads common throughout town, the amphibian population here is surprisingly
large and diverse.
But a number
of factors have taken their toll on amphibians throughout the hemisphere,
including in Colorado—and the drought is only compounding those struggles.
About 39
percent of western hemisphere amphibian species are threatened with extinction,
according to the Global Amphibian Assessment, largely due to habitat loss from
agriculture and development and the rapid spread of a chytrid fungus that has
already wiped out some populations and species.
The long list
of other threats that have made amphibians the most imperiled class of animals
today includes environmental contaminants, climatic changes and invasive
species.
Though
Caribbean and Central American species are the most imperiled, 21 percent of
North American amphibian species are threatened, especially those found at
higher elevations. In Colorado, the boreal toad has been listed as endangered
by the Colorado Division of Wildlife, largely due to the spread of the chytrid
fungus, including on Grand Mesa.
Amphibians
here also face other threats, including diseases and parasites spread by
leeches and ticks, said Steve Werman, a molecular biologist and herpetologist
at Colorado Mesa University.
“Drought
could clearly affect amphibians,” he said. “And if drought weakens them a
little bit, that can stress them and allow diseases and other things to get in.
They would be more susceptible to things they would normally fend off.”
The main
impact from drought arises from the drying up of ponds where some amphibians breed.
After winters
with low snowpacks, such as this year’s, there are fewer of those breeding
sites, according to Stephen Corn, a herpetologist with the U.S. Geological
Survey’s Missoula, Mont., office.
With Colorado
State in the 1970s and early 1980s, Corn studied leopard frogs in the Red
Feather Lakes north of Fort Collins. During the course of those studies,
several populations went extinct following the drought of 1976-77, he said.
“The dry
winters led a lot of sites to dry up over winter, and frogs never really came
back to these sites for the most part,” Corn said. “If we see long-term drought
that really dries up amphibian habitat, that has a chance to have effects.”
The scope of
those impacts depends on species, and species that move to temporary breeding
ponds to reproduce are expected to be impacted less than those that remain in a
permanent habitat that may dry up and leave the animals with nowhere to go.
“You see
expansion and contraction in those species that use temporary habitats, but in
those that use permanent habitats, like leopard frogs, those impacts can be
much worse,” Corn said.
Boreal toads,
he noted, stay in their habitat rather than moving to temporary breeding
grounds, potentially adding drought impacts to their plight.
“Certainly when
you have multiple things, they’ll have a harder time coming back than if it’s
just drought or just fungal outbreaks,” Corn said.
CMU’s Werman
noted salamanders and canyon tree frogs could also be in that category,
potentially stuck with a dried-up pond. The exact extent of that damage will
not be clear immediately, he said, as dry ponds can affect populations both
this year and next.
Spadefoot
toads, for instance, typically stay underground and are fine if there is no
rain, but they can be impacted if they stay underground for multiple years.
“It takes a
long time to see impacts — more than a year,” noted Erin Muths, with USGS’s
Fort Collins office, though she did say one frog pond she studies in Cameron
Pass west of Fort Collins was completely dry already. It usually stays
wet through mid-August.
“The big
thing is these breeding ponds. If these dry up really fast that can really
decimate a local population,” Werman said. “Anything with an aquatic water
stage is going to be hurt.”
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