A team of researchers from the Centre of Wildlife Studies, Bengaluru, have shot down the existing methods of monitoring elephant populations as unscientific. They have instead batted for line transect sampling based on visual detection of elephant clusters to obtain reliable estimates of elephant populations.
Researchers – including Devcharan Jathanna, K Ullas Karanth, N Samba Kumar, Varun R Goswami, Divya Vasudev and Krithi K Karanth – believe the available estimates of elephant populations, particularly in Asia, are often unreliable and misleading.
They have recommended that rigorous line transect surveys with random transect placement, sufficient spatial replication and several other careful field practices can address many of the problems faced by biologists attempting to estimate elephant numbers.
Line transect surveys involve observing chosen paths and manually counting the samples, in this case the elephants. Lead author of the study Devcharan Jathanna said line transect surveys are not new. They have been successfully used by researchers worldwide to estimate wildlife densities. The government and related agencies must change their approach towards elephant monitoring.
The paper, published in the latest edition of Biological Conservation, states that the surveys were conducted from November 2014 to May 2015 and the study areas included Nalkeri, Sunkadakatte and Arikeri located within the Nagarahole, Bhadra, Bandipur, Biligiri Rangaswamy Temple WLS and Kaziranga.
Field work was carried out with permits from Karnataka and Assam forest departments.
Indian forests have nurtured the largest population of Asian elephants. Elephants are severely threatened by conflict with humans as well as habitat loss and degradation. It is therefore essential that the elephant populations are reliably monitored to permit assessments of their dynamics, for the prioritisation of protection efforts and for conflict mitigation efforts at important conservation sites. “Coming up with numbers on elephant population sizes that are not based on carefully collected data is a serious concern from the conservation point of view – especially if those ‘estimates’ affect management decisions,” said Jathanna.
Alternatively, many wildlife researchers in India and Asia prefer indirect methods of surveying population through sign surveys over visual counts of animals. In the indirect methods the density of elephant dung is estimated using standard line transect sampling.
This estimate is thereafter converted to elephant density using estimated rates of defecation and dung decay that are seldom estimated specifically for survey area. Using borrowed rates, or estimating these rates based on small samples can introduce substantial biases into the final density estimate. This could lead to errors in figures.
In the direct transect line method the data is collected by two trained observers walking along the transect line. On detecting elephants, observers record group size, sighting distance, azimuths along the transect line and to the centre of the elephant cluster. As long as certain design, field and analytical prerequisites are met, this approach can give accurate estimates of elephant density.
The authors point out: “Progressing beyond current practices which ignore the best available monitoring approaches appears to be a key management priority at this point for Asian elephant populations that are under serious threat.”
TRANSECT LINE METHOD
In the direct transect line method the data is collected by two trained observers walking along the transect line. On detecting elephants, observers record group size, sighting distance, azimuths along the transect line and to the centre of the elephant cluster. As long as certain design, field and analytical prerequisites are met, this approach can give accurate estimates of elephant density.