Scientists recently released
hundreds of harlequin frogs to learn more about a deadly fungus pushing the
species to extinction.
By Sarah Gibbons National
Geographic January18, 2018
Hundreds of colorful frogs,
barely the size of a palm, have been released into the wilds of Panama in the
hopes of reviving a critically
endangered species.
The variable harlequin frogs,
raised in captivity at a Smithsonian's Conservation Biology Institute facility
in Panama are part of an experiment to see how the amphibians will
fare in a country besieged by a pervasive and deadly disease. The population
has declined by more than 80 percent over the last three generations, and in
Panama, wild populations exist only in some protected areas.
The scientists gave 500 frogs a
unique marking visible under UV light, while 30 additional frogs were released
wearing miniature radio transmitters, says Brian Gratwicke, international
coordinator for the Smithsonian's Panama
Amphibian Rescue and Conservation project and a National
Geographic Explorer.
The Smithsonian team staged a
similar release with another species of harlequin frog last June. Here, one
wears a small radio transmitter. Because of heavy rains, the research team was
unable to take photographs of the radio-wearing frogs from this recent
release.
PHOTOGRAPH BY ROSHAN PATEL
Over the next few months,
scientists will watch closely to see where the black-and-yellow splotched frogs
go—and if they survive.
While the amphibians face some
threats from habitat loss and the illegal trade, by far their biggest threat is
chytrid fungus, which has destroyed many of Central America's frog populations.
HOW THE FUNGUS SPREAD
Found throughout Panama since the
1990s, the fungus feeds on live vertebrates and causes a disease in amphibians
called chytridiomycosis. Scientists believe it primarily affects frogs' skin,
which is how they breathe and take in water. (See 13
Gorgeous Pictures Remind Us Why Frogs Need Our Help.")
In captivity, the disease can be
treated with antifungal medication, but "it's been causing devastating
effects for New World frog populations," says Gratwicke.
In Panama, the fungus caused a
massive frog population die-off and is thought to be responsible for the extinction
of the golden toad.
According to Gratwicke,
scientists believe trade may have facilitated the spread of chytrid. It's
thought to have originated in Mexico in the 1970s before it trickled south to
Costa Rica in the 1980s. (Read
about vanishing amphibians in National Geographic magazine.)
Jonathan
Kolby, a National Geographic Explorer who studies how chytrid
impacts frogs in Honduras, notes that the fungus occurs naturally, but during
the mid 20th century, two different strains mutated.
"What seems to have forced
that change is human activity. Two strains were brought together and created
the global pathogenic strain," he says.
By the time scientists identified
the strain it was too late for much of the infected regions. Once chytrid is
introduced in an environment, it can't be removed without also harming frog
populations.
SEARCHING FOR SAFE HAVENS
Gratwicke and his team hope that
by tracking where the newly released frogs disperse, they can determine where
amphibians are more susceptible to chytrid. The fungus is known to thrive in
cold, moist environments. (Read "The
Search for Missing Frogs Brings Some Species Back From the Dead.")
"The area where we're conducting
the release is a lowland area, and there have been some hypotheses that perhaps
if you release frogs in warmer areas, it might act as a climactic barrier"
against the disease, says Gratwicke.
"If we do collect enough
data," Gratwicke adds, "that would enable us to map refuges."
Kolby is less hopeful that such
regions exist: "I'm not optimistic that there are clearly defined natural
areas to evade chytrid.”
ALTERNATIVE METHODS
Instead, he's looking at how
scientists can manipulate environments to prevent chytrid from growing.
Acidity, for example, is thought to slow down chytrid, and some aquatic
environments can be made more or less acidic based on the level of vegetation.
In rare cases, some harlequin
frogs have also shown resistance to chytrid, but experts don't yet know it the
animals are adapting—or just lucky. (See "African
Clawed Frog Spreads Deadly Amphibian Fungus.")
"The prospects are that the
fungus will cause high mortality in this population," Gratwicke said of
the 530 newly released frogs.
Even so, this population will
help determine where to release more captive frogs in the future.
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