The 18 wild elephants, found dead in Nagaon district of Assam last month, was killed due to accidental electrocution by lightning, the post-mortem examination confirmed.
Various other test reports such as forensic, toxicology and meteorological also suggested the absence of any foul play and pointed towards the electrocution death of the elephants at the Kondoli proposed reserve forest, also known as Bamuni Hills.
The six-member team of experts, formed to carry out the post-mortem examination, submitted their report to the Forest Department of the Assam government on May 27, 15 days after the tragic incident in the Nagaon Forest Division.
"The 18 elephants that were found dead in the Kondoli hills have died due to accidental electrocution by lightning," said the report, a copy of which is with PTI.
The report was prepared after taking into consideration circumstantial evidence at the site, study of gross and histopathological lesions, laboratory reports and correlation with the available meteorological data that prevailed during that period.
The forensic report from the Directorate of Forensic Science said "no poison and its metabolites were detected" inside the dead elephants.
Examining the presence of any toxic substance, the Advanced Animal Disease Diagnosis and Management Consortium of the College of Veterinary Science found that the microbiological analysis of the impression smear could not demonstrate any "anthrax-like organisms".
The Department of Pathology of the College of Veterinary Science under the Assam Agricultural University said in its histopathology report that "lesions are suggestive of high voltage electrical burn injury".
The detailed study of the carcasses of the elephants, which were detected on May 13, estimated the time of the death to be between May 11 late night and May 12 early morning. The herd had eight males and 10 females, including five calves.
The North Eastern Space Applications Centre (NESAC) in its preliminary technical report said that during the time of death, a large number of lightning strikes were found surrounding the area where the bodies of the elephants were found.
"The total lightning flashes reached up to 350 numbers and CG (cloud to ground) flash were 150 in every two hours in between 2-6 UTC. That is a clear indication of the high flash rate over the area and severity of the storm," it said.
The Principal Chief Conservator of Forest (Wildlife) Amit Sahay had earlier said that the preliminary investigation found that the jumbos were killed due to electrocution caused by lightning.
It was found that carcasses were lying in two groups- 14 were lying atop the hill and four were found at the bottom of the hill.
The post-mortem report stated that there were signs of rolling over and sliding on the ground made by the elephants and a few of them were found dead against the trunks of medium-sized trees and bamboo groves.
"Site A (atop the hill) and B (below the hill) were 126 metres apart. From ground evidence, it is evident that carcasses at site B slipped from site A and stuck in physical obstructions like rocks and bamboo thickets," it added.
Nature conservationist Bhaskar J Barua and environmentalist Soumyadeep Dutta were among the several activists who questioned the lightning theory, wondering about the delay in releasing the post mortem report.
"Is the Forest Department trying to hide certain unsavoury truths that might crop up with a proper investigation? How long does it take to conduct a postmortem on an elephant and how long does it take to complete the report?" Barua had said on Facebook.
Dutta had issued a video message and said if the post mortem report is not published by June 5, which is the World Environment Day, then it will indicate that the elephants were killed by "direct or indirect influence" of some officials of the Forest Department.
Elephant expert Bibhuti Lahkar had termed the incident shocking and said it was very rare, and never took place in the Northeast.
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