India: WCS suggests reliable method of monitoring endangered Asian elephant population

Researchers from Wildlife Conservation Society India Program have identified a reliable method to monitor populations of the Asian elephant in the country.

Using the method, they have estimated healthy populations of elephants in some of the well-protected Western Ghats landscape in the south Indian state of Karnataka.

This approach based on direct sighting, as opposed to existing methods, can result in credible and crucial information required to help conserve the country's national heritage animal, say the scientists.

Over 60% of the Asian elephant (Elephas maximus) populations are found in India.

Estimates from the 2012 census spoke of a total number ranging between 29,391 to 30,711 across the 28 elephant reserves. These are based on the dung count method and random block method.

The Elephant Task Force also has recommended that the prevailing census methods be discarded but it continues to be used, say WCS scientists.

Under the method, two survey personnel walk along pre-marked transect lines counting elephants and also recording simple additional information such as distances and compass bearings of the observed animals from their survey lines.

"Visual counts of elephants along line transects works on the assumption that the detection of elephants drops as the distance from the line transect increases. Therefore, by using measurements of distances at which elephants were sighted from the line, we can count them while accounting for detection probability, or in simpler words, the possibility that some animals may be missed while walking the line," Varun Goswami, senior scientific consultant with WCS, and one of the co-authors of the study told IBTimes UK.

WCS India Program has been carrying out long-term monitoring of large mammals, including elephants in the Western Ghats landscape using the method.

Their study estimated elephant population densities in Bhadra, Biligiri Ranganatha Temple, Bandipur and Nagarahole Tiger Reserves in Karnataka.

Devcharan Jathanna, the lead author of the study says, "We examine our own data derived from line transect surveys across a range of habitats, specifically focusing on improvements we made to the survey design and analytical protocols over time… we believe it is practical to implement line transect surveys in many of the elephant reserves in the country, where accurate estimates of elephant population size are important for conservation planning and action."

Most of the currently used methods lack the necessary scientific rigour, says Goswami.

For example, they do not account for imperfect detection of elephants, but instead assume that all animals are seen and counted. This is seldom true, even perhaps in the open savannah of Africa.

Dung extrapolation

To extrapolate dung counts to elephant numbers, there is also need for estimates of dung defecation rates by elephants and rates at which these dung piles decay. Both of these can be difficult to measure and highly variable, thereby leading to potential biases in population estimates.

Only a handful of practitioners use transects to directly count elephants based on visual sightings.

However even the direct sighting method requires to incorporate study design aspects.

"A sound understanding of the distribution and abundance of a species is a prerequisite for devising appropriate policies at the national level and for implementing on-ground conservation actions at the level of each reserve," says Dr K Ullas Karanth, director of Science in Asia, WCS, and a co-author.

The results showed a range of densities from an average of 0.3 elephants per sq km in Bhadra to 2.2 elephants per sq km in Nagarahole.

Elephantine challenges

Rapid industrialisation and human encroachment into forests have shrunk the range of habitat of the 25,000 or so elephants by as much as 70% since 1960, according to environment ministry data.

According to the ministry over 1,177 elephant deaths were reported between 1999 and 2009. Of these, 434 elephants died of electrocution and 106 in train accidents.

Every year, 100-300 humans and 40-50 elephants are killed in human-animal conflicts in India as vital corridors linking patches of forest are taken over by infrastructure projects and human settlements.

Poaching also contributes to elephant deaths, but not on the scale seen in Africa.

Better monitoring would be the first step. Experts tend to look at census numbers as 'guess estimates' at best. A reliable population estimation survey across the country alone can give an accurate picture of the pachyderm.

"We recommend that surveys involving reliable methodology be conducted in primary habitat (protected areas), while elephant occupancy be used as a measure of population/conservation status of elephants in habitats outside protected areas," says Goswami.

The study authored by Devcharan Jathanna, Ullas Karanth, Samba Kumar, Varun Goswami, Divya Vasudev and Krithi Karanth was published in May in the international journal Biological Conservation.

There were believed to be more than 100,000 Asian elephants at the start of the 20th century. Their population is estimated to have fallen by at least 50% over the last 60-75 years, and resulted in the IUCN listing the animal as endangered.