The Cao-vit gibbon is one of the most critically endangered apes in the world, with its entire population living in a single patch of protected forest on the border between northern Vietnam and southern China. Until recently, population estimates for the species stood at 120. Now, a new study published in the journal Nature, calculates that just 74 Cao-vit gibbons (Nomascus nasutus), also known as eastern black-crested gibbons, remain. Researchers say it’s unlikely there was a dramatic population drop; instead, they say they’ve been able to come up with a more accurate estimate by mapping the gibbons’ locations and tracking individuals by identifying the unique song of each male. Gibbons are the only primate, beside humans, known to vocalize or sing. These vocalizations are a core part of gibbon life, often done to alert potential mates or to delineate territory. Previous studies assessed population size by triangulating groups from their songs. However, this method left room for double counting; gibbon groups generally sing in the morning, and could be counted more than once if they moved locations during the course of several monitoring days. The new study recorded and analyzed individual male songs, called “vocal fingerprinting” by the researchers, to differentiate all singing males recorded at 29 listening posts during a two-week period. The study also incorporated passive acoustic monitoring and a drone-mounted thermal camera, which aided in identifying the region’s 11 family groups. Based on observations during the survey and long-term monitoring data, the researchers arrived at a final…This article was originally published on Mongabay
The post Smaller population estimate underscores urgency of saving Cao-vit gibbon appeared first on EnviroLink Network.