Science & Tech

Foraging for forest frogs

7 min read

Sri Lankan frogs worth their weight in gold to science

In the dark of the Sri Lankan cloud forest, the researchers’ only guides
were the headlamps they used to light up the night, illuminating the
cold, gray mist that drifted through the trees.

They looked carefully as
they walked among the trunks, the beams from their headlamps casting
left and right, up and down. They examined rocks and branches, leaf
litter and shrubs, tree trunks, and leaves high in the canopy. By and
by, they found one, then another — small tree frogs that froze in the
light and went suddenly silent.

The frogs are a bit of living
scientific gold. With amphibians declining around the world in what
experts fear is a mass extinction crisis, these recently discovered
tree frogs are strangely abundant and incredibly varied, an overlooked
yet amazing display of biological diversity in a part of the world
where British and Sri Lankan naturalists had worked for a century.

the next two years, Sri Lankan biologist Madhava Meegaskumbura will be
working at the Harvard University Center for the Environment to
understand more about these frogs, studying how they evolved, why they
go extinct, and how to prevent that fate for those that still

“Sri Lanka is on the front lines of the global biodiversity
crisis,” said Alexander Agassiz Professor of Zoology and Museum of
Comparative Zoology
Director James Hanken, with whom Meegaskumbura is
working. “It is among the hottest of global biodiversity hotspots, even
though less than 5 percent of original forest cover remains.  This is
true for the island’s amphibians, and especially tree frogs, which have
undergone a unique and explosive adaptive radiation numbering hundreds
of species.”

Meegaskumbura, a Ziff Environmental Fellow at the Center
for the Environment,  is planning a trip back to Sri Lanka in December
to further his work in the field, which has already astonished
amphibian experts around the world.In 2002, Meegaskumbura, together
with other Sri Lankan scientists and researchers from Boston
University, told the world what they found: as many as 100 new species
of tree frogs in the high cloud forests and lowland rainforests of Sri

The new frog species, most belonging to the genus Philautus,
were found in remnant forests in a part of the island nation that had
been largely deforested by British colonial planters to make room for
plantations of tea, rubber, and cinchona, a tree whose bark is used to
make the malaria treatment quinine.

“I was just completely blown away,”
said Boston University associate professor of biology and herpetologist
Christopher Schneider. “I was completely stunned by the finding. It was
clear that there was this enormous radiation of frogs in Sri Lanka that
nobody had recognized. … I don’t know when the last such discovery was

The work was initially done under the auspices of a Sri Lankan
nonprofit organization called the Wildlife Heritage Trust.
Meegaskumbura joined the effort in 1998 and, together with Sri Lankan
colleagues, helped confirm the unprecedented diversity using DNA
techniques, examining museum specimens, observing behavior of living
specimens brought back to the lab, and logging hours and hours in Sri
Lanka’s high remnant forests.

“There’s obviously so much left to
discover; that’s what’s exciting about Madhava’s discovery,” said
Wildlife Heritage Trust founder Rohan Pethiyagoda.In 1998,
Meegaskumbura contacted Schneider, who became his doctoral adviser and
helped guide several more years of work on the frogs. Meegaskumbura
completed his doctoral degree at Boston University in 2007.

For two and
a half years, Meegaskumbura, mainly together with colleague Kelum
collected frogs and other relevant data in the
forests. The work had to be done at night, when the frogs were active,
and Meegaskumbura worked in the forests from 7 p.m. until 1 a.m. four
or five nights a week, logging hundreds of hours. Researchers
exhaustively detailed what they found, recording frog calls and noting
where each was found, what type of surface it was on, elevation,
humidity, temperature, and other variables that, as they accumulated,
painted a picture of the different species’ habits.

“The diversity of
habitats you have to sample is amazing, places normally you wouldn’t
expect frogs,” Meegaskumbura said.

Researchers also took tissue samples
for DNA analysis and, in some cases, took the whole frog, either to be
preserved as part of a research collection or to observe breeding
behavior in a captive setting.

The forests were often difficult to
traverse. The reason the forests survived is that they are perched on
steep terrain unsuitable for farming. They held hidden dangers, some
natural, some not. Leeches and snakes call the forests home and
Meegaskumbura said he once had a notebook knocked out of his hand only
to turn and see the open, white mouth of the pit viper draped in a
nearby shrub. The snake had struck but hit only the book.

also had to be alert for manmade dangers. Hunters sometimes set up guns
triggered by trip wires to catch wild pigs and other game. A wrong step
could blow away a knee or a hip, depending on the height of the
hunters’ quarry, Meegaskumbura said.

With the conflict between the
government and Tamil separatists having ravaged Sri Lanka for the past
30 years, armed personnel could be another nighttime hazard.
Meegaskumbura recalled one night when trucks full of men began shooting
in the researchers’ direction from a road. He doesn’t know whether they
were shooting live ammunition or not, whether they were hoping to hit
something or just training, but he and his colleagues took cover behind
the trees until the trucks passed, just to be sure.

The research so far
has done more than bring to light the new frog species, Meegaskumbura
said. The DNA work on the frogs has informed science’s understanding of
their relationships to each other, reducing the number of main genera
of Sri Lankan tree frogs from four to two, even though it increases the
number of species within those groups. By searching museums for
specimens of Sri Lankan frogs collected since the late 1800s, they have
identified 19 species that are no longer found on the island and
presumed to be extinct.

“These early reference collections that are now
housed in reputed natural history museums worldwide were instrumental
in highlighting the extinction of species in Sri Lanka,” Meegaskumbura
said.Their studies have shown that most of the frogs are terrestrial
direct developers, Meegaskumbura said. Instead of laying eggs in the
water, most of the new species lay eggs on land, skipping over the
aquatic tadpole phase and hatching as juvenile frogs right from the

Meegaskumbura said he believes this trait may be a key to their
amazing diversity. Being able to have young independent of water, these
frogs were able to venture far from streams and ponds and exploit a
whole host of environmental niches unavailable to frogs whose
reproductive needs tie them to water.“It gives them ecological
opportunity to diversify,” Meegaskumbura said.

Though the frogs don’t
need water to breed, they still need moisture. The misty forests
provide a damp environment for these direct breeders to lay eggs in.
While one type of direct breeder buries their eggs in the forest floor,
protecting them from fluctuations in temperature and humidity, another
type sticks their eggs to foliage and is very vulnerable to drops in
humidity. That characteristic may make them sensitive to changes in the
forest, Meegaksumbura said, either forest fragmentation that dries the
interior out, or to a global warming that might raise temperatures and
lower humidity.

“Global warming could have a devastating effect on these
frogs. These are mountain isolates restricted to small areas,”
Meegaskumbura said. “They could go extinct quite quickly.”

As part of
his work at Harvard, Meegaskumbura wants to develop computer models
that might help predict what kinds of changes the forests and frogs
might face under different environmental circumstances, to help design
conservation policies.

“The Environmental Fellows program was created to
support the professional development of outstanding young scholars
tackling complex environmental problems,” said Harvard University
Center for the Environment Managing Director James Clem. “Madhava’s
extraordinary field research as a graduate student has laid the
foundation for exciting new insights to come as an Environmental