There’s no doubt that elephants are extremely sociable. Orphaned calves are able to console themselves for the loss of their mothers thanks to life in a herd, according to a study carried out on groups living in the wild in Kenya.
Thanks to the stress hormones present in their dung, they have enabled scientists to investigate the consequences of an elephant’s death for her calf, with whom the bond is reputedly strong, even after weaning. The idea came from a young doctoral student at Colorado State University (USA), Jenna Parker, who is passionate about elephants.
“The overall impact of poaching on these extremely social animals is poorly understood,” explains this ecology researcher, lead author of the study published in Communications Biology. “When you observe a herd, you realize how much the family counts. The members are always side by side – the cubs rarely less than 10 m from their mother – they touch each other when they eat, rest, watch each other’s comings and goings… And the reunion ceremonies extended to the whole group, after separations of only a few hours, are incredible”, she elaborates.
Also, when poachers (or hunters) kill an individual, this cohesion shatters, threatening “the well-being of the elephants, especially the calves whose mothers have been killed”.
Jenna Parker and her colleagues wanted to find out how the orphans felt about this bereavement on a physiological level, by studying their stress response. More precisely, by measuring their levels of glucocorticoid hormones, which the adrenal glands of vertebrate animals (including humans) release in response to a stress factor, for example, if an individual feels his or her well-being is at risk in the absence of a secure environment.
These markers are found in blood, saliva, urine… and feces. “Fecal glucocorticoids (fGCM) are a widespread and reliable way of measuring stress in wild animals, as they are non-invasive”, stresses the researcher.
Between 2015 and 2016, she and her team patiently tracked the dung of small pachyderms in the path of herds in the Samburu and Buffalo Springs Reserves (northern Kenya).
This work resulted in the collection of 496 manure samples from 37 baby elephants, 25 of which had lost their mothers. These were exclusively young females (males are harder to spot, as they are less loyal to their herd of origin), aged between 2 and 20 years (around the age of first calving).
The orphans had lost their mothers between 1 and 19 years previously, due to poaching or drought, particularly high between 2009 and 2014. Twenty had remained in the same family unit after death, five had joined an unrelated unit.
The authors found that glucocorticoid levels were similar, over the long term, between orphans and non-orphans. A “pleasant surprise”, recalls the researcher, who had expected orphans to show more stress in the absence of maternal care. This does not prevent them, notes Jenna Parker, from experiencing higher stress in the short term, as has been observed in chimpanzees in the two years following their mother’s death, and even in rats, guinea pigs and certain birds.” But at least these effects don’t last, which shows resilience,” she comments.
The powerful social support of the elephant group would play this regulatory role, known as the “buffer effect”. And there’s more: the researchers found lower stress levels in youngsters growing up in groups with more conspecifics of a similar age, whether orphaned or not. The study suggests that “playmates”, especially siblings, are essential in elephants. These data could shed light on the management of captive elephant orphanages: providing orphans with companions of the same age could help them, and then releasing groups of orphans bonded together during their captivity could ease their transition to the
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