Stress in adult female Asian elephants is influenced by number of calves, finds study

Higher stress observed among jumbo herds that had many calves and few adults

December 04, 2019 10:20 pm | Updated 10:34 pm IST - Kolkata

Social structure in elephant herds is important.

Social structure in elephant herds is important.

Stress in adult female Asian elephants is directly proportional to the number of calves and inversely proportional to the number of adult females in a herd, reveals a study by scientists from Indian Institute of Science, Bengaluru.

The study states that physiological stress on female elephants is significantly influenced by the number of calves and adult females present in the herd, seasonality, and lactational status.

Sanjeeta Sharma Pokharel, co-author of the paper, said, “With a higher number of calves, there’s greater danger of predation, so female elephants have to be more vigilant, whereas a higher number of female elephants in a herd may mean better social bonds, as the presence of experienced adult females or the matriarch results in more effective competitive and defence behaviours to perceived threats.” The other authors of the paper include Polani B. Seshagiri from the Department of Molecular Reproduction and Developmental Genetics, IISc, Bengaluru, and biologist Raman Sukumar.

The scientists recorded stress in female elephants by measuring their faecal glucocorticoid metabolite (fGCM). Glucocorticoids are hormones secreted by mammals during periods of stress.

A total of 145 fresh faecal samples were collected from 123 identified adult female elephants inhabiting the Bandipur and Nagarhole National Parks in south India, between the years 2013 and 2015. “fGCM levels were negatively correlated with the number of adult females (herd size) and positively correlated with the number of calves in a herd and the active lactational status of an adult female. fGCM levels of adult female elephants were higher during the dry season (February to May) than the wet season (August to December),” the study said.

Another interesting observation made in the study was that the levels of fGCM were higher in lactating females than in non-lactating females.

Ms. Sharma Pokharel said that the findings of the study “highlight the importance of maintaining the social structure of elephants in the wild to avoid detrimental effects on their physiological health”.

Insights from such assessments could be used to evaluate the stress in elephants that are involved in direct conflict with humans to take steps for mitigating conflicts, she added. “Management of elephant-human conflicts, such as through selective capture of elephants from herds or splitting herds through chase, could potentially increase stress levels directly as well as through disruption in the social structure of the herd,” the paper states.

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