BENGALURU: A new research study in Nagarhole National Park has revealed that dung-based method of counting elephants and other herbivores is not so effective and needs to be replaced by more robust approaches. According to scientist Ullas Karanth, this study has raised concerns about the reliability of elephant population monitoring using dung-based methods which are presently in use in India and many parts of Africa.
The research conducted by the Centre for Wildlife Studies (CWS) urges evaluating the effectiveness of dung-based approaches in surveying population densities of elephants and other herbivores like gaur, muntjac (barking deer), sambar, deer and wild pig. In collaboration with Foundation for Ecological Research, Advocacy and Learning and Conservation Research (FERAL),UK, the CWS scientists, who tested this dung-based method, found that the estimates were significantly higher than the numbers measured by sighting-based distance sampling.
The study estimated and compared large herbivore densities for chital, elephant, gaur, muntjac, sambar and wild pig. Dung pile counts, decay rates estimated from field experiments, and defecation rates derived from literature were analysed to construct models using a programme.
Dung survey in moist/dry deciduous forests
Wild pig densities were found to be similar in moist and dry deciduous forests, while Sambar were found in a higher concentration in the dry deciduous terrain. The other four species -- gaur, chital, muntjac and elephant -- were found to be higher in moist deciduous forests. The dung survey density estimates were found to be significantly higher than the line transect results in both types of forests.
Senior doctoral fellow, FERAL, and lead author, Ahrestani, said, “Large ungulates are a highly threatened group of animals, and this study was an attempt to calibrate a widely-used, dung-count base monitoring methodology against the rigorous well-established method of line transect sampling. We used large, rigorously gathered data sets on both approaches collected by CWS and performed advanced analysis using statistical models of dung decay rates to derive our conclusions.”
Director, CWS, and co-author K Ullas Karanth said, “The study reinforced earlier research methods that involve counts of animal spoor that these have inherently low information content. It is hard to extract reliable information from such data and calibrate them against rigorous methods which are reliable but very intensive and difficult to implement at extensive scales. “
The study concludes that despite the infeasibility of using direct sightings for population estimates, the simplistic application of dung-based approaches could lead to inaccurate results. So this team of scientists strongly recommend that the use of dung-based techniques must be done by careful consideration of factors. They further urged caution and suggested more robust approaches as density estimates of threatened herbivores need to be reliable for successful conservation action.