Clueless in Chambal

Clueless in Chambal  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.

Corridor of uncertainty
All the deaths have occurred in a 25-30 km stretch of the Chambal river

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.

Schedule I funeral for gharials
The lead and protozoan hypotheses debunked, Brian Stacy, veterinary pathologist at University of Florida, usa, who carried out an on-the-spot post-mortem 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 smaples, 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.

Rotting fish theory While scientists are busy explaining the disease, villagers have a different
 
  Gharial factfile
Zoological name Gavialis gangeticus (last surviving species of family Gavialidae)
Distribution Perennial rivers: Chambal, Girwa, Mahanadi, Brahmaputra, the Gangetic system in India. Karnali, Kali, Kosi and Narayani in Nepal
Size Adult Male up to 6 metres; female up to 4.5 metres
Distinct feature Long, thin snout; bulbous growth at the end of snout
Nesting season March/April
Nest site/banks Highly sloping sand-banks with fine sand
Life span 100 years
Sex determination Determined by incubation temperature; males at 32