Baiji, the Goddess of the Yangtze, is believed to be extinct. An intensive six-week search by experts in late 2006 failed to find any trace of the dolphin in its riverine habitat in China. And while a scientist claimed to have seen a Baiji last week in central China, the sighting has not been officially confirmed.
The disappearance has shaken scientists and conservationists all over the world — one of the reasons why Baiji’s cousins are now under the scanner. And among them is the Gangetic River Dolphin, found in the Ganga, Brahmaputra, Meghna and Karnaphuli and their tributaries as well as in Nepal.
“There are three species of river dolphins left — the Indus Dolphin, the Gangetic River Dolphin and the Bouto of the Amazon,” says R.K. Sinha of the department of zoology at Patna University, who has studied the Gangetic River Dolphin for more than a decade.
Conservationists are trying their best to save the Gangetic River Dolphin. WWF-India — along with the Indian Institute of Technology (IIT), Delhi, and the University of Tokyo — has launched a project to study the river dolphins of India and monitor their population. “Our survey, covering more than 5,000 km of the Ganga and its tributaries, reveals that there are an estimated 2,000 Gangetic River Dolphins in India,” says Sandeep Behera, coordinator, Freshwater Species and Wetlands programme, WWF-India.
The project also uses a novel method to analyse the underwater sounds of the mammal by using hydrophones, a device which enables scientists to hear them. “Gangetic River Dolphins are blind and emit ultrasonic sounds to aid movement. By using a hydrophone to capture these calls, we hope to better understand their behaviour,” says Behera.
Though it was discovered in 1942 that dolphins use sounds for navigation and finding prey, there is much that remains to be understood. These animals emit a beam of clicks that brings forth two kinds of results. “One beam gives the dolphins a fuzzy response regarding the river environment while the other is reflected by a projection of the back of the upper jaw that provides the creature with a clear perception of what lies in front of their open mouths,” elaborates Sinha.
“The hydrophone is a composite pen-like gadget that can detect the individual clicks of a dolphin from within a range of a few hundred metres,” says Rajendra Bahl, team researcher and professor of electronics and acoustics at IIT, Delhi . According to Bahl, this method allows them to monitor river dolphins day and night in a non-invasive manner. “It is better than visual counts since the animals spend 90 per cent of their time underwater,” he says.
The hydrophone system is also being used to monitor Irrawaddy dolphins in the Chilika lake in Orissa. “We have characterised the clicks of the dolphins and developed technology that enables us to locate the creature and find out precise details of its communication methods,” says Bahl.
Dolphins also use echoes to hunt and stay away from danger. “By bouncing sounds off an underwater object and analysing the signal they receive, they can accurately locate an object and determine where it is moving and if it is alive,” says Sinha.
“The present and future of the Gangetic River Dolphin seem to be getting worse by the day,” says Azam Siddiqui, a wildlife researcher in Assam. The animals are being poached for their oil, while sand quarries along the Kulsi river that flows into the Brahmaputra are posing a threat to their movements.
B.C. Choudhary, a scientist at the Wildlife Institute of India, Dehra Dun, is equally concerned. “Industrial plans to start oil exploration in the Brahmaputra will further exacerbate the problem,” he says.
Dolphins migrate locally and the construction of dams and barrages restrict their movement. The animal is also a slow breeder with only one calf being born after a gestation period of 10 months, and this after an interval of two to three years. “The low birth rate means the regeneration of the dolphin population is slow,” points out Sinha. And captive breeding to save this species is not an option as it does not thrive in captivity.
Adding to the woes are regular reports of these creatures being killed and influx of pollutants into the rivers. The Gangetic River Dolphin is an indicator species — a healthy population shows the availability of fish and also helps to determine the level of pollutants and toxicity of the water. Pesticides particularly implicated in environmental and health hazards are those belonging to the organochlorides group and, among these, DDT and its metabolites are the most prominent ones that are found deposited in the dolphins’ bodies, says Sinha.
The WWF-IIT-University of Tokyo team studied the acoustic beam characteristics of an isolated Gangetic River Dolphin that was found in Budhabalanga river in Orissa. This was followed by research on sounds emitted by these mammals in the Ganga near Narora in Uttar Pradesh.
Conservationists and scientists hope that further studies will lead to new approaches to save the dolphin, also called “a living fossil” as it has remained unchanged for almost 20 million years. “We hope to continue our work with WWF India and the University of Tokyo and keep them informed about the movement of these animals,” says Bahl.
If these efforts succeed, the Gangetic River Dolphin may just escape figuring in the list of extinct species.