01/02.2020 | THE SCIENTIST 15marked the beginning of an innovative
reintroduction program that not only
has implications for Montserrat’s
mountain chickens but could inform
the conservation of amphibians around
the planet. By manipulating the frogs’
habitat within the semi-wild enclosure,
Jones and his colleagues hope to sup-
port the population they’ve released and
protect it from disease—and to learn
more about amphibian biology and con-
servation methods along the w ay.
Montserrat hit the headlines in 1995,
when the Soufrière Hills volcano began
to erupt, wiping out two-thirds of the
mountain chicken’s range on the island.
Despite the severity of the disaster, the
frogs survived and continued to thrive
in the island’s northern regions—that
is, until the deadly fungal disease chy-
tridiomycosis arrived on Montserrat
in 2009, probably via the accidental
importation of infected tree frogs. The
disease spread rapidly, decimating the
island’s mountain chicken population
within just one year—the fastest decline
of any vertebrate ever recorded.
Ben Scheele, a population ecologist
at the Australian National University
who recently reported the latest figures
on the disease (Science, 363:1459–63,
2019), says that chytridiomycosis has
contributed to the decline of at least
501 species worldwide. “This estimate
is likely conservative as the disease
has likely also affected undescribed or
poorly known species,” he says. What’s
more, chytridiomycosis is widely rec-
ognized as “the most important cause
of species extinctions” in amphibians,
says Andrew Cunningham, a veterinary
pathologist at Zoological Society Lon-
don (ZSL) who led the team that first
identified the chytrid fungus, Batracho-
chytrium dendrobatidis. (See “A Race
Against Extinction,” The Scientist,
December 2014.)
To date, researchers have been
unable to stop the disease. The fungus
kills amphibians by degrading the ker-
atin in their skin, making it harder for
them to absorb the oxygen and trace
minerals they need for good health and,
in turn, causing heart failure.
Back when the fungus first arrived
on Montserrat, 50 disease-free moun-
tain chickens were swiftly gathered up
and bred in biosecure facilities at zoos
in Europe. In the years that followed,
Durrell Wildlife Conservation Trust—in
collaboration with Montserrat’s Depart-
ment of Environment, ZSL, and vari-
ous European partners—composed the
reintroduction program that Jones,
along with his supervisor Mike Hudson
and the Department of Environment
team, has been putting into action over
the past year.
The frogs’ enclosure contains solar-
heated ponds, areas in which tree can-
opy has been removed to allow the sun
to heat the ground, and large rocks
that the frogs can use as basking sites.
Jones explains that the chytrid fungus
struggles to survive at high tempera-
tures; he and his colleagues hope that
the abundance of warm areas will give
the frogs an advantage over the fun-
gus, and perhaps time to develop resil-
ience to the disease.
One possible route to resilience
could be behavioral adaptation: frogs
that learn to make greater use of hot
spaces might be able to keep their chy-
trid load low enough to avoid harm.
But Jones and colleagues suspect that
there might be other mechanisms—for
example, changes to the epigenome or
to the skin microbiome—that make the
frog’s surface a less favorable environ-
ment for the fungus. On a longer time-
scale, there’s the additional potential
for genetic mutations that promotesurvival to spread throughout the frog
population.
To monitor the project’s success,
the frogs are subjected to a monthly
health check: their sizes and weights
are recorded, and the animals are exam-
ined for any signs of disease. The frogs
are also swabbed, and samples are sent
to ZSL’s laboratory in London to deter-
mine how the chytrid load of each indi-
vidual changes over time. The team has
yet to publish its results, but Jones says
that the return of this charismatic spe-
cies will offer a “beacon of hope” for the
people of Montserrat, who have been
struggling to recover from the volcanic
eruptions that left the capital city bur-
ied in ash some 25 years ago.
Cunningham adds that simultane-
ous work being carried out by other
researchers with genetic material from
a handful of mountain chickens that
survived for years with the fungus in
Dominica—the only other island where
the frog species is found—could aid
conservation plans by identifying DNA
sequences that confer resistance to
the disease. “That could inform selec-
tive breeding or selective releasing on
Montserrat,” he says.
The work could also help researchers
protect amphibians more broadly. “The
experimental management implemented
in Montserrat is very innovative and
exciting,” Scheele says. “Hopefully it is
successful and the approach can be used
to help the conservation of other species.”
But he cautions that “there are no silver
bullet approaches.... We need to try a
range of different things and it’s likely
that different actions will work for some
species, but not be so effective for others.”
Jonathan Kolby, director of the Hon-
duras Amphibian Research and Conser-
vation Center, says that the Montserrat
project represents an important step in
researchers’ fight against chytridiomy-
cosis. “A n y effort which takes that scary
step into the wild... and does any kind
of experimental effort to see how we can
have these animals coexist with chytrid
is a huge step forward.”
—Jennifer ParkerAny effort which takes that
scary step into the wild...
is a huge step forward.
—Jonathan Kolby, Honduras Amphibian
Research and Conservation Center