The Kodaikanal wildlife sanctuary is approximately 650 sq km, which is quite large considering 18 countries on Earth are smaller in area. Surveying an area larger than some countries is not an easy job, and doing so systematically is an added challenge. You may ask how you even go about organising yourself…. the answer is a four letter word…..MAPS!
In the survey business, maps are everything. Knowing how to read and interpret what maps tell us about realities on the ground is absolutely vital. Once we have demarcated an area to be studied on a map, we then break it into smaller bite-sized pieces… quite like how we break up a dosa instead of stuffing it whole down our throats. In our case, we divided the Kodaikanal Sanctuary into roughly 100 cells, each an area of 9 sq km or 2200 acres.
We then looked at individual grid cells and carefully studied their terrain to decide how to approach and survey each cell. Once this was done, the next step was to walk a specifically shaped path or transect through each cell and record signs of mammals along the way.
We would also systematically record data about the nature of habitats and vegetation during the survey. Combining all these data would then give us a more complete picture of how the forests and its inhabitants were faring.
Due to the large size of our cells, it is not possible to cover enough ground with the typical diagonal line transect. We thus decided to use S- shaped transects oriented along specific reference points called centroids to help us navigate each cell in the field.
In this study we placed centroids a kilometre from each other. This meant that to finish surveying a grid cell, we had to walk an eight kilometre long S-shaped path collecting data for eight segments, each 1 km long. Some grid cells needed to be only partially surveyed as parts of a cell sometimes overlapped with farms or other human habitation.
In total we have a hundred grid cells to cover and I’ve got my work cut out for me. With the map and the grid cells superimposed, all that’s needed are some navigation tools and then we’re good to go!
Stay tuned for more on navigation and its importance in a survey in my next post.
1. Dhruv Athreye in February 2018 began a survey of mammals in the Palani Hills and is publishing notes of his field work.