Building Bridges, Not Walls, to Save the Slow Loris
By Shasta Fields
A recent study shows that building bridges, not walls, may be the only way to save a species on the brink of extinction.
A devastating amount of the world’s forest is lost to deforestation each day meaning that the threat to biodiversity is growing. One species in particular, the slow loris, has been greatly impacted by the loss of its habitat. It is listed as critically endangered and one of the major causes of the population’s decline is the expansion of agricultural lands. As forests are converted into farm fields, the result is a patchwork of forest and cropland. This fragmentation makes it increasingly difficult for wildlife to move across the landscape, especially for species that rely on the treetop canopy to move, like primates. Canopy bridges, which are cables hung between trees that are separated by cropland, may be a recent solution to this problem. The bridges provide a way for animals to travel between forest patches without having to move on the ground. While there have been studies on the success of these bridges for various species, there is virtually no research on their success for primates. However, a recent study analyzed the effects of canopy bridges on slow lorises in West Java and the results show that there may be hope.
The Study
In this study, the researchers installed 7 bridges in areas of West Java that are made up of this agricultural and forest patchwork. The bridges were hung in the trees of 2 patches of forest, which were separated by an agricultural field, and they were designed for the lorises to travel between them. Two types of bridges, “loris lines” and “water lines”, were used in order to determine if the primates preferred one over another. “Loris lines” were made of wire coated in rubber while the “water lines” were made of wire attached to a water pipe. Water lines simultaneously served as an irrigation system for the farmland below. At the end of each bridge, they set up a motion-triggered infrared camera to observe the lorises as they crossed. In order to learn about the impacts of the bridges on loris behavior, 7 individual slow lorises were monitored. Each Loris was radio collared and observed throughout the night when they are active. Researchers recorded the number of trees foraged, the amount of time spent traveling, and the amount of time spent on the ground for each loris before and after the bridges were installed.
What They Found
The researchers found that all of the lorises began to use the bridges after a short acclimation period of about 12 days and then continued to use them for the duration of the study. After the installation of the bridges, the amount of time the lorises spent on the ground decreased while the size of their home range increased. This increase was likely because the lorises were able to reach forest patches that were previously only accessible by traveling on the ground. They also found that there was an increase in the number of trees each loris foraged. Additionally, the footage from the cameras on the bridges showed that other species used the bridges to move between forest patches and that there were no incidents of any animals falling from the bridges.
Why We Should Care
The results of this study show that canopy bridges have the potential to be a successful conservation strategy for the slow loris. One of the biggest impacts of the bridges was getting these primates off the ground. More time on the ground means higher mortality from predators, more deaths from vehicle collisions, and higher rates of disease. Another large threat to the slow lorises in Java is the dogs guarding the agricultural fields that they are forced to travel through to reach other forest patches. Therefore, a solution that decreases the amount of time on the ground will help save the lives of many lorises, and this is exactly what the bridges achieve. Not only can these bridges help to conserve slow lorises, but also the many other species that were observed using the cables throughout this study. Although the optimal solution would be to reforest the corridors that separate the forest patches, this is not usually realistic. The private land-owners are most often not willing to give up their land, and controversies about what to plant in reforested areas can slow down the process. At the very least, bridges are a temporary solution that can effectively help to protect loris populations. Additionally, this study showed that the primates do not have a preference between the bridge types and therefore water lines can be used to benefit both wildlife and the local farmers. The water lines can serve as a safe route for animals to move around and provide irrigation systems for the crop fields below. The researchers also used communications with farmers about these irrigation systems as an opportunity to talk about the conservation and importance of lorises in the ecosystem. Any increase in local community involvement in conservation efforts not only increases the likelihood of their success, but also decreases their illegal sale within the local economy. Overall, this study showed that there is hope for the lorises of Java through the implementation of conservation strategies like canopy bridges.
Works Cited
Birot, Hélène, et al. “Artificial Canopy Bridges Improve Connectivity in Fragmented Landscapes: The Case of Javan Slow Lorises in an Agroforest Environment.” American Journal of Primatology, 2019, doi:10.1002/ajp.23076.
Haring, David. Close Up View of a Slow Loris. 13 Dec. 2010.
