As more and more elephant habitats are falling under the ever-growing influence of humans, elephants are often coming into contact with people, whether they are passing through human-inhabited landscapes, or directly interacting with them.
But how do these iconic, endangered giants cope in human-modified habitats such as plantations? Are they stressed in the presence of humans, just like some of us are when we face them? And how do they react to negative conflicts with humans?
To answer these questions, researchers assessed the physiological stress responses of wild Asian elephants in the Western Ghats of southern India. Their findings were both promising and concerning. The good news is that the elephants appeared to adapt to human plantations; the bad news is that they were stressed after being aggressively driven away by villagers. “While they could adapt to changing environments, we show that negative interactions such as drives can be a major cause of stress in these animals,” said Sreedhar Vijayakrishnan, a Ph.D. scholar at Bengaluru’s National Institute of Advanced Studies and the lead author of the study.
Sreedhar Vijayakrishnan’s team measured the concentrations of glucocorticoids, a class of steroid hormones, in the faeces of elephants, which are released when the animals are stressed.
During November 2013 and April 2014, the team scooped up dung samples from 69 elephants belonging either to herds, groups, or solitary individuals, living in two types of neighbouring habitats in the Anamalai Hills: Vazhachal Reserve Forest, a relatively undisturbed evergreen forest, and Valparai plateau, consisting mainly of tea, coffee, and cardamom plantations, along with small forest fragments.
Each year up to 100 elephants use the Valparai plateau. While traversing the plantations, the elephants are sometimes driven away by residents. In these ‘drives,’ elephants are forced back “using tractors, trucks or other loud vehicles, sirens and other noise-making equipment” such as crackers, Vijayakrishnan described. “In Valparai,” he said, “it’s mostly done using vehicles and sirens.” His team compared the glucocorticoid levels before and after the elephant drives to understand how the elephants cope with these intense conflicts.
They found some encouraging results. In the absence of any direct human conflicts such as drives, the stress levels of elephants from the plantation-covered Valparai plateau did not differ from those inhabiting the undisturbed Vazhachal Forest Reserve.
According to Vijayakrishnan, this could be because of adaptation. “These elephants in Valparai have been using this human-use landscape for a long time,” he said. It has been more than a century since the plantation was established and it is likely that the elephants would have come across humans regularly. “In fact, several of these individuals were born in these plantations,” he noted.
But there was a worrying finding as well. The stress levels of the elephants shot up following the aggressive drives. Calves and sub-adults showed the largest increase with glucocorticoid concentrations spiking by 106 and 55 percent respectively, whereas adults displayed an increase of 24 percent.
This might be because adults are more experienced in dealing with these stressful situations than calves and sub-adults, said Vijayakrishnan. The younger elephants, he believes, are “perhaps learning to deal with these situations as they habituate to the changing environments.”IANS/Mongabay
Prolonged stress or chronic stress can pose a threat to their fitness and survival. High levels of stress can disrupt immune responses, digestive processes, and the reproductive system of the elephants.