Taking A Census: - Page 1: Census Frequency & Methods | 2: Accuracy | 3: What Does A Census Show?
India has both an All India Wild Animal Census, and a formal tiger census. On top of this, most National Parks carry out their own count each year. The All India Wild Animal Census takes place every four years and was last done in May 2001. In Project Tiger Reserves the formal tiger census is carried out every two years and is a massive undertaking.
Firstly, the area to be covered is divided into smaller zones, for instance, Kaziranga National Park, is split into 52 compartments. The normal period of any census is 8-10 days and each area is carefully calculated so as to be thoroughly covered during that time.
Staff and volunteers are searching for more than how many tigers are in any given area. They also need to know the sex, age, ratio and density. Using these figures, and the figures from a count of the prey base, staff can calculate how many carnivores a given area can sustain.
Not all parks carry out their census duties at the same time of year. Many used to be carried out in the height of the summer period; this was based on the theory that when the waterholes dried up animals would congregate around the remaining water pockets. It was thought this simplified the task of counting as tigers would naturally follow prey to the water. The system is now considered flawed as it depends upon a couple of false premises:
Neither of these is right and in summer it tends to be even less correct than at other times of the year. Though a few places still use this technique it is increasingly being replaced by taking the census at a time of year when the tiger is at its most active; this is during winter.
The practice of taking a regular census count is well-established within India. For counts of other tiger subspecies it is less often done, though Amur tigers were being counted using the pug mark method over two decades ago. The Hornocker Wildlife Institute also carried out a much needed census of Amur tigers in 1995-1996. It showed somewhere between 330 and 371 cats.
Different counting methods are applied to different animals. For large animals like elephant and rhino the Direct Count method is utilised, while the Specific Sampling method is applied to small and medium-sized herbivores.
In 1932, the world?s first tiger census was carried out in the Palamau forests. It was based on a pug mark count, and is the system still preferred today for both tigers and leopards. This is not because it is considered accurate, but because it is the best of a limited choice of options.
Staff and volunteers are usually supplied with a kit bag containing data sheets, a pug mark tracing board and sheets, a measuring scale, marker pens, adhesive tape, plaster of Paris, and a map showing their pre-determined route.
Pug marks are commonly located near riverbeds, bodies of water, and well-travelled paths. They are followed until a clear imprint is spotted, then traced. If the pug mark is well-defined liquid plaster of Paris is used to take an impression. Up to 18 parameters may be used to determine the individuality of a pug mark.
At the same time the following information is noted:
A back-up method to pug mark tracing involves the use of infrared cameras. These are traps are placed late in the evening on trails known to be used by tigers. They are usually removed each morning for examination and to prevent damage.
An organisation has suggested the use of cameras be extended, especially in the more difficult to count areas like the Sundarbans. The cameras would be placed at different angles along water sources. Photographs of the same tiger taken at different angles would assist in identifying each and every animal. So far no interest has been shown in carrying this out due to the very high costs.
At the end of the census period reports are sent for collation and a final figure arrived at. The documents may then be analysed by a committee and will go on to be used for developing wildlife management strategies in the area.
With Thanks To Aditya Singh