Let’s Count Tigers: Census of Tiger and Leopard

1. What they did

This chapter, based on a note by L. A. K. Singh, describes how the Orissa Forest Department counted tigers and leopards by “pugmark tracking”, and reports the results. The method was first proposed by Saroj Raj Choudhury, used for India’s first all-India tiger estimate in 1972, and refined from 1987 onwards through long-term work in Similipal Tiger Reserve.

It covers:

• Preparation (about 2 months). Census routes are chosen in October and November from earlier censuses, new surveys and the knowledge of forest guards, trackers and villagers. Census units and leaders are assigned, trainers train staff, and non-official volunteers (around 25 in each Similipal census) are trained too. Pug Impression Pads (PIPs) are laid across the routes: patches of sieved dust 2 cm deep and 2 m long, covering the full width of the track, laid in clusters of 3 to 4 at road junctions and every 500 to 1000 m.
• Fieldwork (6 days, 5 to 10 January). Teams walk the routes, checking PIPs, river banks, dry river beds, water-holes, salt-licks and paths. For each pugmark they trace the left hind print onto a glass “Tiger Tracer” and transfer it to a field form, recording location, direction of travel, age of the track and stride. They also make plaster casts.
• Analysis (about 3 months). Tracings are measured for pugmark length (PML) and breadth (PMB), sorted by species, sex and age, and checked against maps to remove duplicate records of the same animal.

The chapter then gives the census results for Orissa and Similipal, and describes the new tiger monitoring method that Project Tiger and the Wildlife Institute of India (WII) began in 2004 and 2005, comparing its results with the 2004 pugmark census.

2. What they found

Reading pugmarks

• Cat pugmarks show a three-lobed pad and four toes; the dew claw on the front foot does not touch the ground. Dog footprints show claw marks and a relatively smaller pad.
• Front pugmarks are larger than hind ones. In a front pugmark the two middle toes reach about the same level; in a hind pugmark they do not.
• Left and right: in a left print the third toe counted from the left leads; in a right print, the third toe counted from the right.
• An adult leopard print is compact, with smaller, narrower toes. A tiger cub print of similar size is more splayed. Leopard stride is longer relative to print length, and cubs’ prints are usually found near their mother’s.
• Sex: a male tiger’s hind pugmark fits nearly into a square (PML minus PMB under 1.5 cm); a tigress’s fits a rectangle (over 1.5 cm). For male leopards the difference is under 1 cm. A front print wider than it is long is a male tiger’s.
• Neighbouring tigers of the same sex and size are only counted as separate animals when peculiarities confirm it, such as a lost toe, heel notch angles or toe spread.

Scale of the work

In 2002, 71 census units in Similipal laid 8946 PIPs over 1773 km of routes and collected 764 tracings and 316 plaster casts.

Population results

• Orissa tigers ranged from 142 (1972) to a high of 243 (1989), then 192 in 2004 (57 males, 75 females, 60 cubs).
• Orissa leopards rose from 260 (1984) to 487 (2004).
• Similipal tigers rose from 17 (1972) to 101 (2004); Similipal leopards from 70 (1989) to 132 (2004).
• The result of each census lists every tiger with its print size, stride and movement area, and links males to females and females to cubs.

The new method

• In January 2006, field data came from 3618 forest beats across 50 divisions. Staff, though new to the method, found 11.6 carnivore signs per km (1647 signs over three days), with a tiger-to-leopard sign ratio of 1 to 1.29.
• Camera traps (15 pairs over 114 km² of southern Similipal, from March 2007) photographed seven tigers and two leopards, and showed melanistic tigers.
• The new method projected 37 to 53 adult tigers in Orissa (pugmark census 2004: 132 adults) and 17 to 23 in Similipal (pugmark census: 69).

3. What they concluded

• Pugmark tracking gives the minimum number of tigers and leopards, the make-up of the population (males, females and cubs), and a map of movement areas that shows where pressure on the habitat is.
• Its success depends on good PIPs, complete field forms, accurate tracings, good plaster casts, and the analyst’s knowledge of tiger biology and the terrain.
• The author lists its advantages: used for over 30 years and improved through research, used in all tiger-range countries, understood by all staff, economical and quick, and it uses and keeps alive people’s traditional skill.
• Leopards may take over places tigers have left, adapt to change and keep up the overall number of large carnivores in a habitat.
• How the new method’s state-wide projections were made is not clear, and the method needs further testing in different habitats. Its camera-trap photos of melanistic tigers support earlier research in Similipal on colour variation in tigers.

4. How tracking was or was not used

Tracking is the core of the method. Teams searched routes and prepared dust pads for tiger and leopard footprints, identified species, front or hind, left or right foot, sex and age from print shape and measurements, read walking gaits and stride, estimated track age and direction of travel, and identified individuals from print peculiarities. Other tiger signs named include kills, claw marks on roads and trees, urine marks, scat and calls. In the 2006 method, carnivore signs were recorded along walked routes.

5. Tracker or observer certification

Not reported. Census unit leaders (forest guards in the example), assistants and non-official volunteers were trained before each census, and the chapter notes that staff who are poor at tracing bring plaster casts instead, but no test of their skill is described. The author states that results depend on the analyst’s knowledge.

6. Other technologies, skills or innovations

• Pug Impression Pads, made with a fine wire-mesh sieve and wire brushes, using local soil.
• The “Tiger Tracer”: a 25 x 20 cm glass pane in a wooden frame for tracing prints.
• Plaster-of-Paris casts, with a recipe and steps.
• A standard census kit and field forms; a database on computer for analysis.
• Refinements made in Similipal in the 1990s: habitat and herbivore data forms, standard season, units, routes and PIPs, and training material in English, Hindi and Oriya.
• The 2006 method: line transects, vegetation and dung plots, Geographic Information System (GIS) mapping, and camera traps (Trailmaster and Deercam).

7. Implications for conservation (from the paper)

• Maps of tiger movement areas show the pressure areas in tiger habitat.
• Tiger numbers naturally fluctuate, but some human impacts could set trends that cannot be reversed.
• The new monitoring method needs more testing before its projections can be relied on.