Amazonia, which extends the vast Amazon River basin in South America, is the largest extent of remaining tropical forest worldwide, home to more animals than any other terrestrial landscape on the planet.
This is because of the very nature of biodiversity in Amazonia, where there is a small number of abundant species and a larger number of rare species that are difficult to observe adequately.
For ecology and conservation, understanding what species are present and how they relate to their environment is of vital importance, since it provides us with essential information on human-induced changes such as climate change, logging, and wood-burning. In turn, this can allow us to adopt sustainable human activities, such as selective logging, which involves taking one or two trees away from the rest.
We are using a wide range of technological fixes, including camera traps and passive acoustic monitors, to overcome these obstacles and enhance our understanding of Amazonian animals. These devices outperform traditional surveys because they are able to continuously collect data without human intervention, allowing animals to go about their jobs unharmed.
The trees' eyes are the focus of attention.
Camera traps are small devices that are activated by changes in behavior in their vicinity, such as animal movements. They have been essential to our fieldwork in the Tapajos National Forest in Para, North West Brazil, allowing us to investigate whether changes such as climate change have altered the presence and behavior of animals, which are in turn necessary to natural processes.
Animal dispersal of seeds, which allows for forest regeneration, is one of these processes. They will usually excrete or drop the seeds elsewhere by eating fruits or carrying nuts.
We also know that many of these animals are directly affected by environmental disturbance. To understand the impact of losing these seed-dispering species, we must understand which ones spread which plants and how far.
On our research site, we have set up cameras at the foot of fruit-bearing trees, revealing which species was eating which fruits, and thus distributing seeds across the forest.
Over 30,000 hours of film were taken, and 5,459 videos contained animals. A total of 152 species of birds and mammals were recorded, including rare records of endangered species such as the vulturine parrot (Pyrilia vulturina).
The videos included amazing insights into animal behavior, such as a ocelot (Leopardus pardalis) after a common opossum (Didelphis marsupialis), a giant anteater (Myrmecophaga tridactyla) carrying an infant on its back, and a curious female tufted capuchin monkey (Sapajus apella) who grabbed a camera and threw it to the floor.
Importantly, we also recorded 48 species eating fruit, including species considered important seed dispersers such as the South American tapir (Tapirus terrestris), which is able to scatter large seeds over longer distances due to its size.
Our study demonstrated that bird species like the white-crested guan (Penelope pileata) and mammals like the Amazonian brown brocket deer (Mazama nemorivaga) are frequent consumers of fruits. Many of these species are overhunted in the study region, which may have an effect on forest regeneration.
Forests are pulsing.
On the other hand, audio recorders are critical to accumulating records of the species-rich bird community. Indeed, although birds are rarely seen in dense forests, their vocalizations reveal their presence.
Ornithologists study tropical birds only when they can do counts as it is often logistically difficult to return to individual sites. Consequently, traditional surveys are often of a rather long duration between 5 and 15minutes, with only a few repeat counts at each surveyed location.
Despite the fact that birds do not all sing at the same time, a few species prefer to sing very early in the morning, most wait until the weather is milder and the sun is fully up, and a few more rise late. Moreover, surveys conducted on a few days mean that factors such as the weather or the presence of predators may completely alter which species are detected.
We discovered that by setting autonomous acoustic recorders to record 240 very brief 15-second surveys totaling one hour of surveying, we could record 50% more species at each location that we surveyed, in comparison to four human surveys that lasted for an hour or so longer. Most importantly, we could record 50% more species at each location we surveyed, all while monitoring the whole dawn chorus.
With a total of only one hour of surveying at each location, we were able to detect 224 species of bird in these hyperdiverse regions.
The diversity of species found in intact and disturbed forests reinforced previous research that showed that undisturbed, primary forests contain unique bird communities that are lost when forests are damaged by selective logging or wildfires.
With over 10,000 hours logged so far, Acoustic recorders have also allowed us to keep track of data over long periods of time.
Collecting data on this scale also means that it is difficult for a scientist to view all of the recordings. Instead, the new field of ecoacoustics has developed statistical techniques to characterize entire soundscapes. These can efficiently process large volumes of acoustic data.
We have used acoustic indices to demonstrate that undisturbed primary forests have unique soundscapes that can be compared with machine-learning techniques. Such data, in turn, allows us to distinguish species groups that have been the most impacted.
Camera traps and acoustic recorders allow us to observe animals in the forest even when our researchers are not there. As technology advances, we will continue to use the latest techniques to understand animal behavior and ecology better and how to better value and protect the habitats they inhabit.
We are working on deep-learning algorithms to identify species and, in some instances, to differentiate individuals from the same species. Automated recorders are opening up new methods for assessing animal abundance and behavior, providing new insights into the mysterious world of tropical forest fauna.
The BNP Paribas Foundation supported Bioclimate, a part of the Climate and Biodiversity Initiative program, and it is coordinated by the Rede Amazonia Sustentavel (RAS).
Oliver Metcalf, a postdoctoral researcher at Manchester Metropolitan University, and Liana Chesini Rossi, an invited user at the University of Sao Paulo State
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