When a report recently declared that there were no tigers left at the Buxa Tiger Reserve in West Bengal, it sent alarm bells ringing. On May 18 and 19, officials from the reserve got together with representatives of the Wildlife Institute of India, the National Tiger Conservation Authority and the West Bengal Forest Department to chart a plan to reintroduce the national animal there.
The reported count was particularly vexing because just three years earlier, the same reserve had announced the presence of 20 tigers. How did the tiger population of a reserve go down from 20 to none in under four years?
The most likely explanation is that those 20 tigers might never have been there.
In 2010, the forest department had approached two organisations, the government-backed Centre for Cellular and Molecular Biology (CCMB) and non-governmental organisation Aaranyak, to genetically analyse samples of scat (or faeces) they had gathered that year. Each organisation received identical halves of the collected scat. That year, Aaranyak found 14 tigers and the CCMB found 15. They repeated the exercise the next year. The NGO found 19 and the CCMB found 20 tigers.
This is where the problems begin.
None of the tigers found in one year of survey matches with tigers found the next. The likelihood of about 34 separate tigers being identified in two separate surveys across two years is close to impossible, even the organisations that tested the samples say.
“We are able to recapture most animals in other surveys as very few animals move out in search of new territory,” said Anuradha Reddy of the CCMB. “This was a whole new bunch of figures and that is something which even I cannot explain. Because of this, we were not able to confidently publish any of our results.”
Data from genetic sampling becomes reliable if researchers get recaptures, she said. The CCMB has done similar studies in central India, where they get many faecal samples of the same animals across years.
If the analysis is accurate, it is possible that either both data samples are tainted or that one or another is.
In the first two years, the Buxa Tiger Reserve independently sent the labs their samples. The labs only handled the analysis phase. After finding that none of the individuals from the first two surveys matched each other, the CCMB sent their own team with forest guards to collect scat samples in 2012. This team photographed every sample they collected.
Aaranyak did not participate in the next two years of genetic analysis. The CCMB, however, has data for 2012 and 2013, which it has not yet been able to analyse for a lack of funds. This data might be crucial to find which, if any, of the previous years had accurate numbers.
The Wildlife Institute of India, which has conducted a comprehensive survey of India’s tigers, also used genetic sampling, but backed it with evidence they collected themselves from the field.
The institute set up 700 camera traps when tracking tigers in 2013, said Qamar Qureishi, who handled the survey in Buxa. In its analysis of scat samples sent by the forest department that year, it found signs of three tigers. However, as it had no visual confirmation of these samples, it declared that there were likely to be no tigers in the reserve.
This raises a few questions. If there were no tigers in Buxa even in 2010 and 2011, where did those scat samples come from? If there were tigers then, where have they gone now?
It is possible that the analysis itself might be inaccurate. Gathering genetic data is tricky. When animals defecate, a part of their intestinal lining containing their DNA might also be excreted. That layer of cells is easily degraded by exposure to heat or wind. It is challenging to find an entire sequence of DNA that can identify species, let alone individuals or their relationship with each other.
DP Bankwal of the National Tiger Conservation Authority dismissed genetic sampling itself as inaccurate, and said it is unlikely they will rely only on this method in the future.
“There is definitely some problem in DNA techniques,” said Bankwal. “There is a discrepancy because the technique has not been perfected. As far as we know, there is no tiger in Buxa, nor has there been any sighting.”
A researcher who requested anonymity disagreed. “You can photograph a tiger from somewhere else, but how do you manufacture faecal samples so that two organisations get the same result?” the researcher asked. “That is not possible.”
West Bengal has no major population of tigers except for those in the Sundarbans. If tiger samples were indeed brought from outside, it would have to be from other states—all of which compete with each other for funds from Project Tiger.
West Bengal’s forest department also believes in the analysis. Buxa is a dense forest contiguous with Jaldapara National Park to its west and Bhutanese forests to the north. According to Azam Zaidi, chief wildlife warden of West Bengal, tigers might simply be on the move from one forest to another.
“Buxa is such a thick forest with sanctuaries in Assam, Bhutan and Jaldapara nearby that it is difficult to find tiger sightings,” he said. “The problem is that we do not have a clear idea of what is exactly there. We are planning to address this with our tiger plan going forward.”
Even if the data is genuine, the outlook for Buxa continues to be bleak. Reddy identified two major problems based on the CCMB data.
One is that the team identified 16 males and four females in 2011. This gender ratio is not promising to sustain a population of tigers. Another is that if the data is accurate, Buxa has a large floating population and it will be difficult to get them to stay in the reserve.
It is very unlikely that this is a repeat of the scam at Sariska, where poachers wiped out an entire population of 18 tigers in six months, the Wildlife Institute of India said.
“This is not an overnight thing like Sariska or Panha where tigers got poached and you can then bring them back,” Qureshi said. “The problem with Buxa is that its prey density has been very low for a very long time, at least since 2006.”
With a meeting to set the reserve back on track, Buxa might soon see tigers again.