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Scientists are developing useful new tools for surveying elusive rainforest mammals

  • A team of researchers used arboreal camera traps and traditional ground-based survey techniques to collect 1,201 records of 24 arboreal mammal species. Six of the species were detected only by the arboreal camera traps.
  • Previous research has shown that canopy-dwelling species might be more severely affected by human disturbance than terrestrial species, and cameras in the canopy could allow scientists to answer the question of whether or not arboreal mammals are being affected in a similar way.
  • Despite what you might expect, deploying arboreal camera traps doesn’t necessarily cost more than traditional survey methods.

In addition to being charismatic flagship species for conservation, arboreal rainforest mammals — monkeys, anteaters, porcupines, sloths — are essential ecosystem engineers that disperse fruits and seeds and act as key rainforest pollinators. Despite their importance, however, there’s a lot we don’t know about these secretive, nocturnal creatures.

Arboreal rainforest mammals have traditionally been surveyed using ground-based techniques like line transects, visual searches, and acoustic surveys. But it’s not easy to see through a rainforest’s dense understory into the upper reaches of the canopy, especially at night, which means that the majority of studies tend to focus on more conspicuous species that are vocal and active during the day, resulting in incomplete knowledge of tree-dwelling mammal communities.

But researchers working in Peru’s Manú Biosphere Reserve say that they have demonstrated the effectiveness of using arboreal camera traps to survey the charismatic and threatened rainforest mammal species that often go under-studied.

“This is the first scientific peer-reviewed publication where we display the potential of arboreal cameras to inventory mammals in a typical forest environment and directly compare their efficiency and cost with traditional ground-based survey techniques,” the University of Glasgow’s Andrew Whitworth, lead author of the study, published Monday in the journal Tropical Conservation Science, told Mongabay.

White-fronted capuchins captured by an arboreal camera trap. Image courtesy of Andrew Whitworth.

Whitworth and a team that also included researchers from Peru’s Universidad Nacional San Antonio Abad del Cuscoas as well as the UK’s University of Exeter accumulated 1,201 records of 24 arboreal mammal species. 18 of the species were detected by arboreal cameras, while seven were detected by diurnal line transects, six by nocturnal transects, and 18 by incidental observations. Most importantly, six of the species were detected only by the arboreal camera traps.

The silky pygmy anteater is one of Whitworth’s favorite examples of the effectiveness of placing camera traps up in the trees. The species is a tiny, nocturnal anteater that lives in the canopy and is incredibly difficult to spot.

“I have never seen one in eight years of living and working in the Neotropics and neither had any of the researchers working at the Crees Foundation’s Manu Learning Centre since [their] research began in 2003,” Whitworth said. “However, with just 18 cameras in the trees for about three months, we had two videos of this fabulous little species. The ‘holy-grail’ of arboreal rainforest mammals, for me at least.”

Whitworth prepares to descend after installing a camera trap in a tree’s canopy. Image courtesy of Andrew Whitworth.

Though the study was focused on mammals, Whitworth and team also captured a number of birds and reptiles on the cameras. “We had one video of an incredibly rare species of canopy-dwelling lizard, unseen in the flesh by many experienced herpetologists, myself included,” he said. “It was awesome to see this little dude running around 25 meters up in the canopy showing a very cool territorial, head-bobbing display.”

Despite what you might expect, deploying arboreal camera traps doesn’t necessarily cost more than traditional survey methods. “A cost-effort analysis indicated that despite greater upfront costs in equipment and training for arboreal camera trapping, when accounting for the additional survey hours required to provide similar numbers of records using ground-based methods, overall costs were similar,” according to the study.

Over the past couple decades, there has been an explosion of research using camera traps for terrestrial species of rainforest mammals all over the world, which has allowed scientists to begin to understand distribution patterns, population densities and changes, and new behaviors, giving them a glimpse into the secret lives of rainforest animals. Those studies have also yielded important insights about the impacts that human activities and habitat change are having on terrestrial rainforest animals — but our understanding of these impacts on the broader ecosystem has been limited by the fact that canopy camera traps are still not widely used.

Endangered black-faced spider monkey. Image courtesy of Andrew Whitworth.
Red howler monkeys. Image courtesy of Andrew Whitworth.

Whitworth believes that it’s time for that to change. His research on rainforest butterflies has shown that canopy-dwelling species might be more severely affected by human disturbance than terrestrial species, and cameras in the canopy could allow scientists to answer the question of whether or not arboreal mammals are being affected in a similar way.

“This is super important as scientists around the world suggest that we have entered an era now termed the ‘Anthropocene,’ in reference to the significant impact that we have had, and continue to have, on our planet,” he said. “If we don’t react quickly, not only in our solutions to the problems we are causing but in developing new tools to rapidly assess what is happening to wildlife, many species could go extinct, with little chance of us really knowing.”

Knowing what’s happening with canopy-dwelling mammals is especially crucial given their role in dispersing many rainforest trees and plants. “As much recent research has shown, the health of the world’s tropical forests is essential in combating climate change through the storage and uptake of carbon, and arboreal animals are important guardians of this forest function and health,” Whitworth added.

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