Saving Species Through Sound

On the canopy of Hainan Province’s tropical rainforest, a female Hainan gibbon and her infant are perched. [Photo/China Daily]

 

Acoustic monitoring helps Hainan environmentalists track rare gibbons.

 

In the heart of Hainan’s tropical rainforest, the daily routine of the Hainan gibbon begins around 6 a.m., when the male leaders of the five remaining groups issue their loud, melodious calls, which echo through the dense, mist-shrouded forest and reach the villagers below. The valley floor lies at an elevation of roughly 800 to 1,200 meters.

 

“Whistling has been interpreted by zoologists as a way for each family to mark its territory, and as the matriarch and other family members join in, the chorus grows richer and more harmonious. This is among the most moving examples of collective singing exhibited by the remaining 20 gibbon species,” said Chen Qing, a forest ranger by trade who recently retired after more than 37 years of service at the Bawangling National Nature Reserve in southwestern Hainan Island.

 

Bawangling Nature Reserve was established in 1988, covering approximately 300 square kilometers, and serves as the sole habitat of the Hainan gibbon (Nomascus hainanus).

 

The world’s rarest primates currently number only 35 individuals, divided into five families.

 

Bawangling is an integral part of Hainan Tropical Rainforest National Park and represents the best-preserved tropical rainforest in China, covering 4,269 square kilometers—about one-seventh of the island’s total area. According to the park’s management authority, more than 95 percent of the park consists of pristine primary forest, home to 3,653 species of wild vascular plants and 540 species of terrestrial vertebrates.

 

The enchanting calls of the gibbons are currently being recorded in real time by 50 high-tech devices mounted in the trees and transmitted to cloud‑based storage. In January last year, the Hainan National Park Research Institute and the International Union for Conservation of Nature launched an acoustic database project aimed at better protecting the park’s flagship species by using data to decipher their vocalizations. The deputy director of the project is from the School of Life Sciences at Hainan Normal University.

 

“These devices, built on Huawei’s Tech4Nature technology, can automatically recognize the calls of Hainan gibbons. When one of the gibbons vocalizes, the devices are triggered and begin recording,” he said.

 

According to media reports, Huawei’s system is being deployed in 30 national parks worldwide and has been awarded by the United Nations for its outstanding contributions to nature conservation.

 

This photo was taken on August 29, 2020, at Dongbengling in Baisha Li Autonomous County, Hainan Province, southern China, showing a female gibbon embracing her infant. [Photo/CCTV News]

 

Organize audio cues

 

“The Hainan gibbon is born with a golden coat and spends its entire life in the trees, performing most of its movements in ways similar to humans. Its arms are much longer than its legs, and it feeds on fruits, bird eggs, young tree leaves, and insects—high up in the canopy, about 15 meters above the ground,” said Chen, who is well acquainted with most of the species and plants found in tropical rainforests.

 

“In the 1980s, the gibbon population plummeted to fewer than ten individuals, comprising just two families. They were easily startled and lived in a fragile environment. But in recent years, they have grown bolder. Now, if we happen to encounter them during routine surveys, they’ll curiously stare at us from just a few meters away.”

 

However, tracking gibbons remains challenging. Conservation efforts continue to face significant hurdles; according to Wang, at present, the most effective method for monitoring gibbons is acoustic monitoring.

 

“Like humans, the vocal cues produced by Hainan gibbons can be decoded to identify specific individuals. Advances in automated acoustic data‑collection methods—such as wireless transmission and networked storage—are helping to build acoustic databases for gibbons and other vertebrates, enabling researchers to map out their linguistic structures and communication patterns,” Wang said.

 

“Combining data analytics with behavioral image monitoring will help us better understand their lifestyles and the ways they express emotions such as joy, anger, and sadness.”

 

Acoustic monitoring devices, which emit no light and thus do not disturb or interfere with forest wildlife, are well-suited for long-term, large-scale, real-time operations and have become a popular tool for biodiversity monitoring both domestically and internationally.

 

Analyze data

 

Over the next six months, Wang and his team of ten will collaborate with experts in cloud storage, artificial intelligence algorithms, and voice‑print analysis—among them Huawei—to analyze the data collected over the past year.

 

Subsequently, they will prepare a preliminary report on the acoustic characteristics of gibbons and endeavor to interpret their daily behaviors while more accurately identifying their habitats.

 

“The database is expected to be completed within three years. It will play a crucial role in the comprehensive biological research and conservation efforts for gibbons and other rare species in Hainan’s tropical rainforests,” said Wang, the project leader.

 

He noted that the acoustic monitoring project is the first of its kind in China, designed to track all major rare species within a single protected area.

 

In several national parks, including the Northeast China Tiger and Leopard National Park, the Xishuangbanna Nature Reserve in Yunnan, and the Giant Panda National Park, integrated monitoring systems comprising remote-sensing satellites, drones, and ground-based equipment have been deployed to track flagship species across these areas, according to environmentalists.

 

They suggest that, in the future, conservation research on the Hainan gibbon could be expanded to encompass explanations of its behavior, rather than focusing solely on communication.

 

For example, how they choose their mates helps deepen our understanding of human evolution.

 

They also proposed collecting phenological data, including information on fruit tree species favored by gibbons, as well as details about their predators and competitors.

 

Since 2005, Hainan has restored over 330 hectares of gibbon habitat and planted approximately 300,000 fruit- or leaf-bearing trees favored by gibbons. The area of protected habitat has expanded from 21.4 square kilometers in the 1980s to 4,269 square kilometers today, according to the park administration.

 

The steady recovery of the Hainan gibbon population is clear evidence of the achievements China has made in ecological and environmental protection in recent years.

 

Jane Smart, Global Director of the IUCN Biodiversity Conservation Group, stated that the province’s conservation efforts have rekindled confidence in the future of protecting endangered primates worldwide.

 

Professor Tang Yanfei, Executive Director of the Hainan National Park Research Institute, stated that, in accordance with the Hainan Gibbon Conservation Action Plan, the province will establish a specialized monitoring system and strengthen both domestic and international cooperation in research on gibbon conservation and community‑based sustainable development.

 

Tang believes that, with new advances in scientific research, habitat restoration, and the enhancement of rainforest ecological corridors, the Hainan gibbon population will double by 2035, reaching approximately 60 to 70 individuals.

 

(From ChinaDaily)