Improved Approach to Tiger Counting through Pugmarks

1. What they did

Tigers are hard to see, so their numbers cannot be counted directly. In India they have been counted from their pugmarks (footprints) since the first All India Census of Tigers in 1972. In the 1990s the method was attacked in the media, and in 1996 the WWF Tiger Conservation Programme asked the author, then Research Officer at Similipal Tiger Reserve, to write guidelines for pugmark tracking that could be relied on across the country.

In this short paper, written up from a seminar talk in Calcutta in January 2000, the author:

• Traces the history of the method, from F. W. Champion, who tracked tigers in the 1920s, to S. R. Choudhury’s Tiger Tracer of 1970, a device for copying a pugmark onto paper so it can be taken from the field for storage and analysis.
• Lists why the method was criticised, and answers each main criticism.
• Sets out the improvements made since 1990, the subjects still needing research, and what the pugmark technique can achieve.

2. What they found

Why the method drew criticism

The author sees the pugmark technique as reasonably sound, but some criticism was genuine and some came from avoidable situations:

• Wildlife management was new and known to only a few people high in the hierarchy.
• Answers to the criticisms did not reach field staff, and some field workers were unclear about the concept.
• The procedures were not written simply (for example, telling left from right, front from hind, and male from female).
• The method was not transparent.
• Managers wanted to present an “all is well” picture.
• People tried to interpret tracings or plaster casts without enough skill or field information.

Main criticisms and the author’s answers

• Population growth seemed too fast. About ten years after Project Tiger began, tiger numbers had risen in almost all habitats, and people doubted the estimates. The author says it is now agreed that such growth was possible under strict protection and habitat management.
• Identifying individual tigers. The claim that all individual tigers are identified from pugmarks is “a little premature”. Individual identification is only needed in a few cases, such as pugmarks of equal size from two neighbouring census units. Where two sets of tracks cannot be told apart, it is safe to count them as one tiger, because the aim is the minimum number of tigers.
• Ground conditions. Pugmarks vary in depth, size and clarity with the soil. Pug Impression Pads (PIPs), with about 1 cm of fine dust, give a stable, uniform surface. In deeper soil or mud the outline is drawn along the middle line between the upper and lower levels of the print, which can also be done from a plaster cast.
• Tracings vary from person to person. Field staff of the Forest Departments do the tracking and tracing, and they are not always good at tracing. Staff are now asked to bring a plaster cast as well as a tracing, so the print can be retraced to a uniform standard.
• Interpretation varies from person to person. The most cited criticism is an experiment in which a few people counted tigers from a set of plaster casts and got different results. The author says this happened because field data were incomplete: information on field conditions and the tiger’s movement is needed for analysis, and is now recorded on a set format (Form-D).
• Cubs are undercounted. Usually only one cub, rarely up to three, can be identified from pugmarks, so cubs are underestimated. The author repeats that the aim is a minimum population size.
• Telling male from female. The traditional rule is that a hind pugmark that fits a square is male, otherwise female. Since a perfect square is rare, this caused arguments. A ready-to-use table now gives sex from the length and width of the hind pugmark, and sex can also be identified from the front pugmark.
• Tiger cubs and adult leopards. Their pugmarks are almost the same size but differ in the relative size and arrangement of the toes, which takes experience to judge. Stride is now also being considered.
• Awareness of what the figures mean. Media criticism, better standardisation and staff training have changed this, and the author says the change shows in tiger figures from different parts of the country.

Improvements since 1990

• Clarity and transparency through “non-official participation”.
• Simpler procedures that all field staff can understand.
• Verification through PIPs.
• Standardised season, census unit, route and PIP placement, data collection, training, analysis and presentation of data.
• The full procedure in print in English and Hindi, and in Oriya, the local language; illustrated pocket books for field workers in progress; a training video in Oriya being tried; and trainers’ reference sheets, tracking guidelines and a pictorial field guide.

Still needing research

Avoiding the undercount of tiger cubs, telling leopard cubs from lesser cats, and improving on the present under-coverage of the area.

3. What they concluded

• The author concludes that the pugmark technique, well practised, can identify species, sex and major age class, link males with females and mothers with cubs, and map territories and movement areas: all parts of a tiger population’s dynamics and biology.
• The technique also gives local employment and protects a traditional skill.
• Understanding of the technique improves every year, but it still needs further research and may need refining for particular sites.

4. How tracking was or was not used

The whole paper is about tracking: counting tigers from their pugmarks, recording prints by tracing and plaster casts, laying Pug Impression Pads on routes to get clear prints, and reading pugmarks for species, sex, age class and individual identity. The author also lists kills, scat, ground scratches and tree scratches as evidence of tigers, but says pugmarks are the most common and the easiest to use, verify and interpret. No new tracking data are reported.

5. Tracker or observer certification

Not reported. The author says field staff of the Forest Departments do the tracking and tracing, and that they “are not always good at tracings”, which is why plaster casts are now asked for and training has been introduced at all levels. The acknowledgements thank “local skilled trackers of the country”. No certification or test of skill is described.

6. Other technologies, skills or innovations

• The Tiger Tracer (S. R. Choudhury, 1970), for tracing pugmarks in the field.
• Pug Impression Pads (PIPs): patches of about 1 cm of fine dust laid on routes to give uniform prints that can be checked.
• Plaster casts of pugmarks, used to retrace prints to a uniform standard.
• A standard field format (Form-D) recording field conditions and tiger movement.
• A ready-to-use table for sexing tigers from hind pugmark length and width.
• Training material in English, Hindi and Oriya, including pocket books and a training video in Oriya.

7. Implications for conservation (from the paper)

• Sound data on population status give conservation its base and direction; tiger numbers are a measure of how well conservation actions are working.
• The author reports that tigers and their habitat responded well to strict protection and habitat management in the first 10 to 15 years of Project Tiger, and that the situation is now stabilising as tigers compete with people for space and resources.