The mystery of gharial deaths in the Chambal waters continues to elude scientists.

More than 90 of the critically endangered species have died since early December, all within a stretch of about 25 km of the river flowing along the Uttar Pradesh- Madhya Pradesh border. Nobody seems to know the reason. In a January 28 meeting of the Crisis Management Group, set up by the union government to look into possible causes and draw an action plan, veterinarians and conservationists could not pinpoint the causes of deaths.

Etawah-based NGO Society for Conservation of Nature reported the first death in the first week of December 2007. By the end of the month, 40 gharials had died. Alarmed, the forest department sent samples of viscera and water to the Indian Veterinary Research Institute (IVRI) in Bareilly for testing toxins and disease.

Though most of the gharial carcasses found were partially decomposed, on-the- spot post-mortems revealed liver cirrhosis, as indicated by scarred and damaged liver. "After death, the carcass first sinks and then surfaces after a few days; by then it is partially decomposed," says Dhruva J Basu, gharial conservation coordinator at WWF India. IVRI scientists suspect a protozoan parasite found in viscera analysis damaged the liver and kidney in gharials. But crocodile experts rule out this possibility. "Protozoan and other parasites are common in crocodiles and other aquatic reptiles, and do not cause mortalities," says F W Huchzermeyer, a veterinary consultant and co-chair of veterinary science with the World Conservation Union's Crocodile Specialist Group. R J Rao, gharial researcher at Jiwaji University in Gwalior, echoed his views.

The IVRI report also showed high levels of lead in gharials. It can't be said for certain if these levels (0.7-1.4 ppm) are fatal. "At this level, lead can act as immunosuppressant but cannot cause mortality," says D Swarup, scientist at IVRI.

There is another problem: absence of baseline data for comparison, even after 30 years of conservation. Gharials are found only in India and Nepal. The only comparison for lead levels right now is with Chinese alligators.

Conservationists say high levels of lead in gharials could be from eating contaminated fish. Water and fish samples from the Chambal showed high levels of lead for the first time recently; it has no known source of lead. But it meets the Yamuna 40 km downstream of the affected area. Forest officials say contaminated fish and water could come upstream from the confluence. The lead and protozoan hypotheses debunked, Brian Stacy, veterinary pathologist at University of Florida, USA, who carried out an on-the-spot postmortem of a gharial, says there are indications of gout in gharials, possibly due to kidney failure. Huchzermeyer says if this is so, it is shocking because kidney infection, and hence gout, is very rare in gharials. Lala A K Singh, gharial expert of the Orissa forest department, says though gout is uncommon in natural crocodilian populations, it is common in captive-bred animals. He recalls a 1977 incident when most of the 400 gharial hatchlings brought from Nepal died. The symptoms were similar. Even then, the cause of deaths remained inconclusive.

Again lack of baseline data comes in the way. Huchzermeyer says he wants to study a live, healthy gharial for having baseline data but the Wildlife Protection Act, 1972, does not allow this because gharial is a Schedule I species. On February 2, vets were allowed to collect urine and blood samples, which won't provide much useful data.

For the time being the scientists are focusing their investigation on diseases. Members of the Crisis Management Group have ruled out human interference and are not looking at the possibilities of poaching and reduced prey base. The dead gharials had no signs of external injury and post-mortem results indicated that deaths were not due to drowning in fishing nets, a common causes of death. Scientists also rule out poisoning of the river because the fish and other aquatic animals had not died.

Huchzermeyer has another hypothesis: "The deaths may have been caused by pansteatitis, a condition caused by consumption of rotten fish." It has killed South African crocodiles in the past. Pansteatitis causes hardening of the animal's fat, leading to reduced mobility and death by starvation in six-eight weeks of consuming dead fish. "The degeneration of the liver tissue caused by this condition can appear similar to the signs of cirrhosis, which may account for preliminary diagnosis of cirrhosis," says Huchzermeyer.

While scientists are busy explaining the disease, villagers have a different explanation. "They are dying of starvation. Extensive illegal fishing has reduced fish in the river to such an extent that big gharials are not getting enough food," says a resident of Sahnso village in Etawah. The forest department has confiscated fishing nets in the region. "I have reports of people blasting under water to kill and catch fish in large numbers," says Rajeev Chauhan, secretary general of the Society for Conservation of Nature: "Gharials might have eaten leftover dead and rotten fish," he explained. This dovetails with Huchzermeyer's hypothesis.

IVRI scientists also found that in most cases the gharrial's stomach was empty. But conservationists rule out starvation, saying there is enough prey base in the river for gharials. Filmmaker Naresh Bedi, who made the first documentary on gharials, says this claim is not based on studies of the prey base.

It is worth noting that all the deaths occurred between the bridge at Sahnso and Udi village in Etawah. This stretch is part of the 400 km of the river protected under the National Chambal Sanctuary. "The stretch has a high density of gharials. Due to illegal fishing and continuous human presence, there is a possibility that gharials are not getting enough time for basking," says Rom Whitaker, chairman of the Gharial Conservation Alliance, an independent international mission.

Before this episode, less than 200 breeding gharials were estimated in the wild. Basu points out that all dead gharials were longer than two metres-mostly breeding animals. Ten were males; gharial populations are skewed in favour of females, and a small reduction of males can bring them to the brink. Forest officials stress that all the deaths occurred in the 'natural population', as opposed to captive-bred animals released into the wild. Bedi doubts if there is a survey to ascertain the number of captive-bred gharials surviving in wild.

The gharial was on the verge of extinction in the 1970s. Since the inception of Project Crocodile in 1975, which included captive breeding, several thousand captive-bred gharials were released into the wild. Only a few survived. The present crisis questions the knowledge and conservation approach of the Union Ministry of Environment and Forests, which is again planning to launch a project to conserve gharials, which are on the IUCN Red List. "This time we will focus on the gharial in its natural habitat rather than going for captive-breeding," promises Pramod Krishnan, joint director, wildlife, at the ministry.

-Down To Earth Feature Service