Wild Sumatran orangutan mothers display distinct and consistent parenting behaviors, a new study by the Max Planck Institute of Animal Behavior (MPI-AB) has found. Over 15 years of research revealed that these differences persist across multiple infants, even after accounting for biological, social, and environmental factors. The findings, published in the Proceedings of the Royal Society B Biological Sciences, suggest that orangutan mothers may possess individual “maternal personalities.”
The study analyzed six maternal behaviors, including body contact, carrying, and feeding proximity, in 22 mother-infant pairs at Indonesia’s Suaq Balimbing research site. Researchers observed that some mothers carried their infants more frequently, while others terminated body contact sooner. These tendencies remained consistent across different offspring, highlighting individualized parenting styles.
As infants grew, mothers adjusted their behaviors flexibly, but the degree of adjustment varied. For example, all mothers reduced proximity as infants aged, but some did so more markedly than others. “These differences stayed consistent across the different infants of a mother,” said lead author Revathe Thillaikumar, emphasizing the uniqueness of each mother’s approach.
Sumatran orangutans have the longest infant dependency period among nonhuman animals, making maternal behavior critical for offspring survival and skill development. The study’s senior author, Caroline Schuppli, noted that the findings open questions about how these parenting differences might affect infant development, a topic requiring further long-term research.
“Orangutan mothers are not all the same when it comes to parenting behaviors,” said Thillaikumar. Schuppli added, “The consistent differences among mothers suggest they may possess individual maternal personalities.”
The study underscores the complexity of orangutan parenting and its potential impact on infant development. Future research will explore whether these behavioral differences influence offspring outcomes, but answers may take another decade of data collection. For now, the findings offer a fascinating glimpse into the diversity of maternal care in one of humans’ closest relatives.
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