Most National Parks in the country hold their individual tiger counting operations almost every year. The All India census is however, held less frequently. The last was held in the year 1999 and the next is to be held in May 2001. The tiger census is an operation of huge proportions. Each park is first divided into numerous zones. It is kept in mind that it should be possible to completely cover each of these by the staff and volunteers during the 8 -10 day period. The main factors on the basis of which the counting is done are pugmarks. This method is now under a lot of discussion as many experts feel that it is not a very accurate means of determining the true number of tigers in the country. They feel the same tiger can leave a variety of pugmarks, depending on factors such as the speed of travel, the slope of the ground, the hardness of the ground, the tiger carrying a kill, etc. Until a concensus is arrived upon by the authorities on the best alternative method, pugmarks will continue to be the main indicators of how many tigers survive in the wild.