Amazonian Nights

Researching bats in Brazil's rainforest

In October 2013, National Geographic Portugal magazine published my story "Amazon - Reborn from the Ashes",
a fourteen-page article on the largest and longest-running ecological experiment up to date.
For two and a half months, I stayed in encampments like this one, under the evergreen canopy of the Amazon rain forest, alongside an international team of field ecologists. We were working the night shift to study one of the most diverse and fascinating groups of mammals - bats.
On the second week of expedition, nights at "Km 41" were a little less intimidating under the bright full moon.
As Ricardo promptly told me when I first joined the project, this is the same camp where Sir David Attenborough
stayed while filming the Capuchinbird for the Life of Birds series.
As the debate over the minimum size for nature reserves heated among the scientific community in the 70's, a young conservationist decided to take the matter into more practical terms. By isolating patches of forest with different sizes, Thomas Lovejoy kickstarted the largest-scale ecological experiment up to date - the Biological Dynamics of Forest Fragments Project.

The set he picked for his endeavor was nothing less than the biologically megadiverse lowland terra firme rainforest, in the Brazilian Amazon. Thirty years later, the project continues to yield precious insights into how plant and animal communities respond to forest fragmentation. 
The team I'm working with is solely and enthusiastically dedicated to studying the long-term impacts of habitat fragmentation on tropical bats. Until the end of April I'll be joining biologists Ricardo, Adrià, Fábio and Gilberto in their efforts to understand how to better conserve these wonderfully diverse animals.
​​Around 160 species of bats live in Amazonia and through the course of evolution they have made sure
to take the most out of every resource available. Rhinophylla pumilio is a particularly common species
on areas of fragmented forest, feeding on the fruits of pioneer plants.
Studying bats is a difficult task. Bound to the dark, they can weigh as little as 5 grams and fly higher than 50 meters. Whenever the rain softens, hundreds of them forage the forest by night. But if we were to rely on our senses we would only aspire to see them for a split second as they dash by or momentarily hear their characteristic yet discrete calls.
To be able to identify which species live inside the fragments, Ricardo and Fábio set up at least fourteen nets every night, from 6pm to midnight. "For the first time, we'll be able to observe how bat communities have behaved in 35 years of isolation". Ricardo who has been in Amazonia for two years, also adds that "it's incredible to be part of a project with a study area as large as the island of Madeira!".
After setting up all 14 ground nets, Ricardo and Adrià finish preparing a canopy net just before dusk.
These nets hang from branches up to 35 meters in height allowing researchers to study species that
find their niche on higher layers of the rain forest.
The sites match those of Erica Sampaio, a scientist from Tübingen University who led a similar study in the 90's. This will allow Ricardo and his team to also compare how 15 years of forest regrowth have affected bat communities. "Changes are already evident. Many species of gleaners, which are more sensitive to fragmentation, are coming back."
At every netting point, researchers mount a small portable table with everything they need to identify,
weigh and measure every bat. Everything is done as fast as possible, particularly on busy nights,
when the number of captured bats may rise to 300.
During the day, the team carefully organizes the genetic samples collected the night before.
Each contains two bits of skin collected from either wing. 
A few families of bats however have an extremely acute sense of echolocation - to them nets are simply too obvious barriers. To overcome their anonymity, researchers rely on alternative approaches. This is Adrià's area of expertise.
At precisely 6pm, Adrià turns his headlamp off and his ultra-sound detector on. It will record the call emitted by a wide array of species, many of them insectivores of the most elusive kind. "You may find this a little less exciting than the nets" told me Adrià when we first teamed up. "But since we stand still most of the time, you do get to see more animals."
An Anolis lizard - the first of many animals that Adrià and I found during our surveys. Fairly common,
these lizards rely on their camouflaged patterns to go unnoticed.
Recording along transects is only a small part of Adrià's quest. To achieve his goals, Adrià must resort to the latest technology in bat research - automatic detectors. Installing these devices usually means walking for hours to reach remote parts of the forest and leave them working for several nights in a row. "Very little is known about the ecology and behaviour of insectivores and much less about the long term impacts of fragmentation. These detectors allow me to record and identify almost every bat that forages the forest, including species that fly high above the canopy."
Adrià's dearest goal is to build an open access data base of call descriptions for as many species
of neotropical bats as possible. Concentrating inumerous mosquitoes, lakes are havens for insectivores and
thus come first in Adrià's list of favourite places to record these secretive animals.
In Amazonia, venturing into murky still waters is a risky business. The reason why Adrià doesn't think twice about it
lies in the fact that lakes offer him the opportunity to catch and identify species that are never captured inside the forest.
"Bats are less aware when they swoop to drink water so even the most skillfull of echolocators may fail to spot the net."
Artibeus lituratus, one of the largest bats we caught during my stay in Amazonia.
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