Elephants graze in Kenya's Amboseli National Park.
One more proof of the extreme sociability of elephants: the little orphan pachyderms manage to console themselves for the loss of their mother thanks to life in a herd, according to a study carried out on groups living in freedom in Kenya.
It was stress hormones found in feces that allowed scientists to investigate the consequences of an elephant dying in her calf, with which the link is reputed to be powerful, even after weaning.
The idea came from a young doctoral student from Colorado State University (United States), Jenna Parker, who is passionate about African savannah elephants, a species classified as endangered on the United States' red list. #x27;International Union for Conservation of Nature (IUCN), due to poaching and habitat destruction.
The overall impact of poaching is poorly known on these extremely social animals, explains to AFP this researcher in ecology, main author of the study published this week in Communications Biology.
“When you look at a herd, you realize how much family matters. The members are always side by side – the little ones rarely within 10 meters of their mother – they touch each other when they eat, rest, watch the comings and goings… And the reunion ceremonies extended to the whole group , after separations of only a few hours, are incredible.
— Jenna Parker, ecology researcher, lead author of the study
Also, when poachers (or hunters) kill an individual, this cohesion is shattered, threatening the well-being of elephants, especially in the calves whose mothers have been killed.
Jenna Parker and her colleagues wanted to know how orphans feel this grief on a physiological level, by studying their response to stress. More specifically, by measuring their level of glucocorticoid hormones, which the adrenal glands of vertebrate animals (including humans) release in the face of a stressor, for example if an individual feels their well-being is in danger due to lack of energy. a safe environment.
These markers are found in blood, saliva, urine… and excrement. Fecal glucocorticoids (fGCM) are a widespread and reliable way to measure stress in wild animals, because they are non-invasive, the researcher points out.
With her team, she therefore patiently tracked, between 2015 and 2016, the manure of small pachyderms on the passage of herds from the Samburu and Buffalo Springs reserves (northern Kenya).
A work that made it possible to collect 496 samples of manure from 37 baby elephants, 25 of which had lost their mothers. Young females exclusively (males are harder to spot because they are less loyal to their herd of origin), aged 2 to 20 years old (approximately the age of the first calving).
Researchers found lower stress in young people growing up in groups with more peers of a similar age.
The orphans had lost their mothers between 1 and 19 years previously, due to poaching or drought, which were particularly high between 2009 and 2014. Twenty of them had remained in the same family unit after the death and 5 had joined an unrelated unit.
The authors found that glucocorticoid levels were similar over the long term between orphans and non-orphans. A good surprise, recalls the researcher, who expected that the orphans would 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 the death of their mother, and even in rats, pigs d'India and some birds.
But at least these effects do not last, which shows resilience, she comments. The powerful social support of the group of elephants would come to play this regulatory role called the buffer effect.
And there is more: the researchers found lower stress in the young 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 findings could inform the management of captive elephant orphanages: providing similar-aged orphans could help them, and releasing bonded groups of orphans together during captivity could ease their transition back to the wild, the study concludes.