Saturday, May 26, 2007

Royal Tigers: Can counting techniques save them?

This is a scientific technique I am gonna pen down, I have no expertise in this and don’t know the nuances of the issue also. It’s a simple effort to scribble the info available in the literature and books and online.

Its not only the media, concerns are all over India and world about steep decline in the tiger population in India. In general tigers are a species which is demographically distributed among 13 Asian countries. It is one of the rare royal species which is about to be extinct. In India there are 28 reserve forests for tigers and tiger census are carried out frequently. Wildlife Institute of India, Dehradun, came with a shocking revelation recently. they published a census report for tigers in 16 of these forests (rest they are going to publish in December 2007). It was shocking because they had reported a decline in tiger population by 60% in Madhya Pradesh, 57% in Maharashtra and 40% in Rajasthan. This decline took place within few years and the concern is, it happened in spite of govt. action to safe guard India’s national animal. Steady decrease in the no. is attributed to poaching and decrease in the habitat area. These big cats are extinct because of their big size and carnivorous diet which force them to reside in low population area. They are easy and prize targets for the poachers and reduction in the food availability is forcing them to be extinct, but there is other side of the story too: Some people believe that previously published census data was erroneous. In Palamou reserve forest the number of big cats may vary from 7 to 37! This takes us back to the process of counting the tigers. There is couple of techniques I am concentrating on here

Pug mark counting technique

This is quite old technique for tiger census; it was first used by W. J. Nicholson of Imperial Forest Service in Palamau district, Bihar in 1934. Then on this technique has gone through many versions of reforms and is still it is a topic for research. In this technique pugmarks separated by long distances are considered as individual tigers; among these the hugely varied marks are discarded. Using a multiple group discrimination technique it is possible to identify the track of individual tigers. It was found that seven such carefully identified pug marks can give a more or less accurate no. By the way pug marks are the footprints, shape of which gives the info of the gender too, usually individual cats follow different tracks , hence once the track is identified its is easy to count the no of tigers in a forest. It’s a time taking but an inexpensive method

Photo trapping technique

It’s a brain child of Dr. Ullas K. karanth, who is now in Bangalore. Pugmark technique although is being followed for quite sometime, it’s not a visual counting technique and secretiveness can not be taken care of easily. In this photo trapping technique, cameras are fixed near the track, as it is said that the stripes on the tigers body is similar to human face, hence it is possible to distinguish the tigers from the pictures and identify them next occasion. Tiger densities are calculated using statistical methods. Line transect sampling is used to find the tiger density. It is quite an efficient technique although several issues are still debated.

Except these there is a waterhole technique which is used in counting the number of tigers, but the important issue here is: is this counting technique varies the census results? Interestingly WII has used the photo trapping technique during the current census whereas the previous censuses followed the pug marks. In addition, forest official not always try to publish the factual info, just to avoid the exhibition of the decline in the no. of the tigers. Hence it’s quite a difficult blame game, but truth is tigers are in declining no. whether it is Suderbans or Ranthambore, they are endangered. Someone says correctly: it’s a losing battle!


lala said...

I am glad to see your interest in tiger numbers. I have studied tigers and refined the pugmark technique during my 16+years tenure in Similipal Tiger Reserve, Orissa. The sincerity with which the staff conduct pugmark tracking and the type of data produced from pugmark tracking is unmatchable. No other method can surpass pugmark tracking. It is quick, it allows us to know the movement area of each tiger and leopard, their population structure- male, female, cub with pugmark sizes (hence, idea about age class too), links among cub-mothr, female-male; their spatial distribution map; it is economic, it employs local tribals who skill in animal tracking. A Guard, at the end of census is able to know, which exact tigers are in his territory and in his neighbouring territory. There is no statistical extrapolation, hence no mathematical tigers. Do you need a copy of the WWF guideline? send your e-mail address. My address:;
Book title:
Singh, L. A. K. (2000): Tracking Tigers : Guidelines for Estimating Wild Tiger Population Using the Pugmark Technique. (Revised Edition). WWF Tiger Conservation Programme, New Delhi.

Anonymous said...

Hello to everyone. Yeh its a very sensitive and difficult time for all of us thinking about the sorry state in which our National Animal stands at.
I am Ashis, a young wildlife Biologist. I was a member of the All India Tiger Estimation team of Wildlife Institute Of India, who came up with the latest count and the 'real trith'of the indian tiger population and its habitats through the Camera Trapping Method using state of the art technologies and highly advanced wildlife investigating softwares.
My team did this Camera Trapping in five Tiger Reserves (Similipal, Rajaji, Corbett, Dudhwa and Ranthambhore)
We all find the Pugmark census method to be very genuine and gives authentic facts, if and only if conducted properly. But who does it? does the scientist having the experties goes from forest to forest to collect pugmarks? NO. But who does it at the field level? Do we possess enough equally informed, well equipped foresters at the range or beat level? Do we train them enough to estimate correctly?
And thus we have been witnessing an over-estimation of the “truth”. Yes numbers make us happy, make the system happy and help the funds flow, but it is high time we must accept the truth, the “Project Tiger” is a failure.
Then in late 90s a revolutionary and advanced scientific method was introduced, known as “Camera Trapping”, which almost changed the way we used to estimate the tiger population. People like Dr Ullas Karanth, Dr. YV. Jhala, James D.Nicholos worked very hard to standardize the method to suit Indian forests.