Monitoring Tigers in the Twenty-First Century India-Part VI
Here is the sixth part of an article published by Shri Vinod Rishi in
The Indian Forester. Vol.136:10. Wild Life Special.
Shri Vinod Rishi is IFS – retd. and a Former Additional Director General of Forests (Wildlife), Govt. of India; E-mail: firstname.lastname@example.org
(Continued fro last month)
The experimental evaluation of field methods (Karanth, 1987).
Because the field methodology for tiger censuses depended on the identification of individual tigers from their foot-prints, an experiment was also conducted for its validation in a zoo. In it, 33 pugmarks tracings were obtained on two different substrates
from four captive tigers, and presented for census to 6 wildlife managers, who were claimed to have been actively involved in such work and gained experience ranging between 4 to 12 tiger census years.
The participants made 72% statistically significant correct choices in distinguishing the pugmark impressions of left and right, front and hind feet, and of male and female tigers. But the participant with 12 years of tiger census experience declined to identify
the tigers. The rest of the five participants, having 4 to 6 census years of experience, could not identify a single tiger from the pugmarks, and the number of tigers counted by them from the tracings ranged between 6 and 24.
Based on the above discussions, the Review concluded that the field methodology was unreliable. (Karanth, 1987).
Revisiting the Controversy
(1) Evaluation of the Basic Premises for Field Censuses
Certain premises had been made before discussing the research based arguments in the review of the field censuses. There were misconceptions apparent in the premises because the literature did not support them. Some of the basic premises were:
(a) S.R. Choudhury had argued that every tiger could be individually identified from its pugmarks.
Choudhury neither denied, nor argued in favor of pugmarks; he is on record having cautioned the users that “Much rigorous and prolonged practice in the field is necessary to be able to distinguishing from similar looking pugmarks, different tigers in the same
or contiguous localities…A pugmark on sand or deep fluffy soil often looks very different from its true shape and size…if true tracings of pugmarks were taken from comparable soil conditions then it is one of the very confident parameters to be collected.”
(b) The investigator asserted there was no validation carried out of the field method.
The literature shows that the Co-operation Census Technique was validated by S.R. CHOUDHURY by carrying out control and field trials in Delhi Zoological Park on Nov 21 & 22 1970; in Khara and Chilla forests from Dec 2 to 17, 1970; in Nandankanan Biological
Park on Dec 28, 1970; and again in Khara and Chilla forests from Jan 27 to Feb 11, 1971 (Choudhury, 1970b, 1971).
(c) The investigator treated two different methods as one and the same:
-To be Continued
Monitoring Tigers in the Twenty-First Century India-Part VII
Here is the seventh part of an article published by Shri Vinod Rishi in The Indian Forester. Vol.136:10. Wild Life Special. Shri Vinod Rishi is IFS – retd. and a Former Additional Director General of Forests (Wildlife), Govt. of India; E-mail: email@example.com
(Continued from last month)
S.R. Choudhury’s Co-operation Tiger Census method (Choudhury, 1970a, 1970b. 1971, 1972a, 1979b) and Pugmark method (Panwar, 1979a) differed on several counts. The apparent similarity of the two methods is superficial and
it ceases at the use of tiger-tracer for tracing pugmarks. The literature based comparison between the two indicates:
i. Co-operation Tiger Census used spatio-temporal analysis of the signs and evidences of tigers and their territorial behavior to estimate status of tiger populations: “The parameters of the census are the strong territorial habit and the methodical movements
of the average individual” (Choudhury, 1970b); the Pugmark Census method used tiger pugmarks as the primary index for estimating tiger populations in an area (Panwar, 1979a).
ii. The tools used in Co-operation Tiger Census included a network of serially numbered Pad-impression Pads (PIPs) for providing uniform soil and ground conditions at all data collection sites to avoid the problem of tracing of representative pugmarks from
variable soil substrates, and to facilitate transfer of data to a processing map; standardized Counting Sheets provided, besides other data entry spaces, a small rectangular frame on its front to mark the presence and absence in, or movement of tigers in the
direction of the adjacent Counting Units; and carrying on its reverse a history matrix for the enumerator to log in, by place, date and time, the evidences or sighting of tigers over the week prior to the census exercise. Pugmark Census technique had done
away with such an elaborate field level system of checks and cross-checks.
iii. The Co-operation Tiger Census used bunching of tracing sheets by serial numbers of pad-impression pads and of Counting Sheets, which reduced the number of tracings to be compared at a time for elimination of duplication of counts. Pugmark Census method
depended on personal judgment of skilled enumerators to eliminate duplication in counts from the examination of shape, length and breadth of pugmarks, and average stride and straddle of tiger, and required comparison of a large number of pugmarks at a time
for eliminating duplication in counts.
(2) Evaluation of the Census Data
A revisit to the Review revealed that there were basic errors committed in the analysis of the data. These were:
i. Error in the Use Of 1972 Figures As A Bench-Mark
for Calculation of Growth Rates:
a. The census of 1972 did not give a complete picture of tiger population in India. It had missed quite a few tiger populations in the eastern and the north-eastern parts of India. Sankhala, the first Director of Project Tiger, made an estimate in 1972 placing
the figure at 2,000 tigers in India (Sankhala, 1978). The tiger census of 1972 could not be completed in the Sunderban tiger reserve of West Bengal (4/5th of Sunderbans not covered), the Manas tiger reserve in Assam and the Simlipal tiger reserve of Orissa
in eastern India. There were other areas in north-eastern India, too, where census had missed tiger populations, e.g., Mizoram recorded the presence of 15 tigers in 1977 as against no information in 1972; Manipur registered presence of 16 tigers in 1977 as
against 1 reported in 1972. (Srivastava, 1979).
b. New areas had been added to some tiger reserves after the 1972 census. For instance, Kanha National Park was expanded to 940 km2 by 1974 from an initial area of 318 km2 at the time of first all India census in 1972 (Panwar, 1979b). The numbers of tigers
in such areas in 1972 as happened to get added to the earlier figure of 1972 for tiger reserves were not adjusted.
Because of the indeterminate, but substantial number of missed out tiger populations in the 1972 census, the use of incomplete census figures for calculation of growth rates from the complete census figures of 1984 was scientifically unsound.
-To be Continued