Tropical forests cover 12% of the planet’s land surface, but are home to about two-thirds of all terrestrial species. The Amazon, which stretches across the vast Amazon River basin and the Guiana Shield in South America, is the largest expanse of the tropical forest remaining globally and harboring more animal species than any other terrestrial landscape on the planet.
It’s always a challenge to spot wildlife in these dense, dark forests teeming with insects and thorny palm trees.
This is due to the very nature of biodiversity in the Amazon, where there are a small number of abundant species and a larger number of rare species that are difficult to census properly.
Understanding what species are present and how they relate to their surroundings is of fundamental importance for the ecology and conservation of the Amazon, providing us with essential information on the impacts of the disturbances caused by the man, such as the climate change, the tala or the quema wooden. In turn, this may also allow us to return to sustainable human activities, such as selective logging, the practice of removing a tree or two and leaving the rest intact.
as part of BNP Bioclimate Project We are implementing a variety of technology solutions, such as camera traps and passive acoustic monitors, to overcome these obstacles and refine our understanding of Amazonian wildlife.
These devices outperform traditional surveys with their ability to continuously collect data without the need for human interference, allowing animals to continue their business undisturbed.
Eyes among the trees of the Amazon
Camera traps are small devices that are triggered by changes in activity in their vicinity, such as animal movements. They have been essential to our fieldwork in the Tapajós National Forest in Pará, northwestern Brazil, allowing us to investigate whether disturbances such as climate change have impacted the presence and behavior of animals which, in turn, are necessary for natural processes.
The dispersal of seeds by animals, which allows forest regeneration, is one of these processes. When eating fruit or carrying nuts, they normally excrete or drop the seeds elsewhere. Our search showed that at least 85% of all tree species in our plots have their seeds dispersed by animals.
We also know that many of these animals are heavily affected by disorders. To better understand the impact of the loss of these seed-dispersing species, we need to know which ones spread which plants and how far.
videos
We tried to see this by placing cameras at the foot of the fruit trees at our study site, revealing which species ate which fruit and thus carried seeds through the forest.
The search resulted in over 30,000 hours of footage and we were able to determine that 5,459 videos contained animals. An impressive total of 152 species of birds and mammals have been recorded, including rare records of endangered species such as the vulture parrot ( vulturine pyrilia ).
The videos included incredible information about animal behavior such as an ocelot ( Leopardus pardalis ) hunting a common possum ( Didelphis marsupialis ), a giant anteater ( Myrmecophaga tridactyla ) carrying a baby on its back, and even a curious tufted capuchin monkey ( Sapajus calls ) who checked a camera and ended up throwing it on the floor.
It is important to note that we also recorded 48 frugivorous species, including species considered important seed dispersers, such as the South American tapir ( tapirus terrestris ), which is able to scatter large seeds over greater distances due to its size.
Our research showed that bird species such as the white-crested guan ( penelope pileata ) and mammals such as the silver marmoset ( Myco argentatus ) and the Amazon deer ( Mazama nemorivaga ) are frequent consumers of fruit. Many of these species are overhunted in the study region, which can generate cascading impacts for forest regeneration.
Pulsating forests of the Amazon
Acoustic recorders, on the other hand, are critical for compiling inventories of the species-rich bird community. In fact, although the birds are rarely seen in dense forests, their vocalizations reveal their presence.
When ornithologists study tropical birds, they are limited by how often they can perform counts, as it is often a logistical challenge to return to individual sites. As a result, traditional searches are often quite long in duration, between 5 and 15 minutes, with only a limited number of repeated counts at each searched location. This means that only a small proportion of the time period when Amazonian birds are most active, the two hours after sunrise, commonly known as the dawn chorus, can be monitored.
However, not all birds sing at the same time: some species prefer to sing very early in the morning, most wait until it is a little warmer and the sun is very high, and some wake up late. By limiting ourselves to a few surveys, it is difficult to cover the entire time period and detect all species present. Furthermore, surveys carried out in just a few days mean that factors such as the weather or the presence of predators on certain days can completely change which species are detected.
Our search found that by setting up standalone acoustic recorders to make 240 very short 15-second recordings, totaling one hour of study, we were able to record 50% more species at each sampled site compared to four 15-minute studies that replicated the study duration. human. The additional surveys allowed us to extend our survey period to more days, but most importantly throughout the entire dawn chorus. We found that there was a small group of species that preferred to sing from 15 minutes before sunrise to 15 minutes after, and we would only be very likely to detect them if we had multiple surveys in that period, something that is only possible with automatic recorders.
Huge Amazon Data Collection
These more complete studies allow us to provide better estimates of the species that live in these hyperdiverse regions, but also of those that disappear when forests are cleared or burned. Thanks to this method, we were able to detect 224 bird species in 29 locations with a total of just one hour of study in each location.
Species present in intact and disturbed Amazonian forests also confirmed our previous research, showing that undisturbed primary forests harbor unique bird communities that are lost when forests are damaged by selective logging or wildfires.
Acoustic recorders have also allowed us to collect data over long periods of time, with over 10,000 hours recorded so far.
However, collecting data on this scale also means that it is not feasible for a scientist to listen to all recordings. Instead, the new field of echoacoustics has developed statistical techniques to characterize entire soundscapes. These acoustic indices measure variation in amplitude and frequency to provide a metric of how busy or varied each soundscape is. By eliminating the need to identify individual sounds, they can efficiently process large volumes of acoustic data.
We use acoustic indices to show that undisturbed ancient forests have unique soundscapes that can be identified with machine learning techniques. These data allow us, in turn, to contrast soundscapes that have been disturbed by phenomena such as fires or logging and to distinguish the groups of species that were most affected.
understand to preserve
To conclude, camera traps and acoustic recorders allow us to have eyes and ears in the forest even when our investigators are not there. As technology develops, we will continue to use the latest techniques to better understand the behavior and ecology of animals and how to use them to better value and protect the habitats they live in.
In particular, we seek to develop deep learning models to identify species and, in some cases, differentiate individuals of the same species. The sights and sounds recorded by automated recorders are opening up new ways to understand the abundance and behavior of animals, providing new insights into the secret world of rainforest fauna.
This article was written by Oliver Metcalf, a postdoctoral research associate at Manchester Metropolitan University, and Liana Chesini Rossi, a PhD student in Ecology and Biodiversity at Universidade Estadual Paulista. It is republished from The Conversation under a Creative Commons license.
For Times of Sustainability. Article in English