(ORDO NEWS) — For any child, the appearance of a brother or sister is a time of struggle for parental attention! As it turns out, this behavior also exists in the animal kingdom.
Scientists at the Max Planck Institute for Evolutionary Anthropology, Germany, have found that bonobos, a species of great apes, are also jealous of their parents for their siblings.
Biologists studied monkeys in Salonga National Park, an isolated rainforest reserve in the Democratic Republic of the Congo, Central Africa.
According to the data, young bonobos experience a lot of stress when they have a brother or sister, and cannot get rid of this feeling for seven months.
It has long been known that young bonobos have a strong bond with their mothers; if they are separated too early, there is a great risk that the cubs may even die.
How was the study conducted?
“In mammals with slow ontogeny [approx. ed .: the development of the body] the birth of a brother or sister marks an important transition in their development, ”say the authors of the work.
“Behavioral studies indicate that this event is stressful for older offspring, but the physiological evidence for this is insufficient, and it remains unknown whether the birth of a sibling is stressful beyond simple weaning.
Our findings indicate that the transition to extended family life is stressful beyond nutritional and social weaning.”
As part of the project, the team studied the offspring of 20 female and six male bonobos, aged two to eight years, living in the wild.
Scientists closely monitored both physiological and behavioral changes in children’s behavior after the appearance of a brother or sister.
Physiological changes included changes in levels of cortisol, a key stress hormone, as well as neopterin, a marker of immunity found in urine, indicating presence in the blood.
Other behavioral changes related to the mother-infant relationship and feeding outcomes (sucking, riding on the mother (embracing her), closeness, body contact, self-foraging).
The team found that with the birth of a new sibling, neopterin levels dropped and cortisol levels in older offspring increased five-fold. These cortisol levels remained elevated for seven months, regardless of age.
Scientists conclude that animals have a long time to adapt, because they used to live in a world where they had almost unlimited access to parental time and attention, and now they have to share it.
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