Enumerations of Tigers and co predators have always been challenging task. Over the years several new methodologies have evolved to provide credible numbers to especially of Tigers. Until recently tiger census was used to be done by traditional pugmarks method. The pugmark method though combined with good field observation used to provide good results but had several shortcomings. With the advent of modern technology the census is being carried out through camera trap and DNA based methods using scats as they are more reliable and scientifically sound techniques.
Buxa Tiger Reserve was one of the first reserve in the country to adapt census or enumeration of Tigers and co predators through scat DNA technique. The first such exercise started from the year 2007. In this method entire protected area is divided into census units comprising of 2-3 compartments. Census teams comprising of 4 staff and NGO members is formed which will travel through these compartments along patrolling paths, trail nalas, fire lines etc. While doing so they collect 1-10 day old scats of Tiger and co predators in plastic pouch filled with silica gel and record GPS location of place of collection. Then it is sent to Division headquarter for further screenings. This kind of sampling is done over 1-45 days and is repeated 2-3 times. Such collection scats are scanned of division level and sent to labs for Genetic analysis by keeping portion of sample as representative sample. The detailed methodology of genetic analysis of scat is presented hereunder.
2007 Census-Scat DNA Analysis Method :
Enumeration of Tigers in 2007 in Buxa Tiger Reserve was mainly done through pug mark method, but during the course in addition some tiger scats were also collected and were sent to Wildlife Institute of India for genetic analysis. During this exercise altogether 39 scats [23 from BTR (E) and 16 from BTR (W)] were collected and were sent to WII, Dehradun for further analysis. Genetic analysis of scats by WII revealed the minimum population of tigers to be around 12 comprising 6 female and 4 male and 2 cubs.
2010 Tiger Census- Scat DNA Analysis Method :
Considering the limitations of pugmark method and on the basis of encouraging results from WII in 2007, in the year 2010 Buxa Tiger Reserve adopted scat DNA method as main method for enumeration of Tigers. In total 83 scat samples were shortlisted and were sent to CCMB, Hyderabad and Aranyak, Guwahati, two renowned laboratories for analysis. The results were very encouraging. The total number of tigers after analysis by both the institutes stood at 15 with not so encouraging sex ratio.
2011-Tiger Census –Tiger scat DNA Analysis Method :
On the basis of encouraging results of last year tiger scat DNA analysis method and on the recommendation of the CCMB and Aranyak as to the need of repetition of the exercise to arrive at consistent figures on the number of tigers in Buxa Tiger Reserve it was proposed to repeat the tiger scat collection and sign survey in 2011 in 3 phases starting in the month of January and till April with a gap of 25-30 days between each phase.In total 240 scats were collected and were sent to two labs i.e. CCMB, Hyderabad and Aranyak, Guwahati. After analysis CCMB revealed the presence of 20 individual tigers with sex ratio of 16 male and 4 female. The study revealed the presence of three tigers in Jaldapara National park also.
2012-Tiger Census –Tiger scat DNA Analysis Method :
In continuation of earlier efforts in 2012 also the tiger census was carried out by way DNA scat analysis. The exercise was done in three phase from November to February and in total 468 samples were collected which included scats of leopard and other cats from Buxa Tiger Reserve and Jaldapara National park. Preliminary report form CCMB suggested that out of 468 scat samples collected from Buxa Tiger Reserve (3 sampling occasions) and 34 from Jaldapara WD-III (2 sampling occasions) between December 2011 and March 2012, 178 from Buxa Tiger Reserve and 15 from Jaldapara National Park were found to be positively of tiger origin. The final results are awaited.