New research on wild Sumatran orangutans reveals that mothers have distinct, consistent parenting styles—hinting at individual maternal personalities in one of our closest relatives.
Key Points at a Glance
- Sumatran orangutan mothers show stable, individual differences in how they care for their infants.
- These differences persist across multiple offspring and years of observation.
- Mothers vary in how flexibly they adapt their behaviors as their infants grow.
- The findings suggest orangutans may possess individual maternal personalities.
- Further research is needed to determine how these differences affect infant development.
In the dense rainforests of Sumatra, where the canopy forms a world of its own, orangutan mothers cradle, carry, and guide their infants through years of slow, deliberate development. Now, a 15-year observational study from the Max Planck Institute of Animal Behavior has uncovered a surprising truth: not all orangutan mothers parent the same way.
The study, conducted at the Suaq Balimbing research site in Indonesia, followed 22 mother-infant pairs over more than 6,000 hours of observation. The results show that maternal behaviors like carrying, maintaining body contact, staying in proximity, and feeding near the infant vary significantly between individuals. And these behavioral patterns remain consistent—not only across time but also across multiple infants born to the same mother.
“We found that some mothers consistently carried their infants more, while others were more likely to end body contact or allow their infants greater distance,” explains lead author Dr. Revathe Thillaikumar. “What was most striking is that these patterns were stable even when accounting for external influences like environmental conditions or infant age.”
Orangutans are known for having the longest dependency period of any nonhuman animal, with infants staying close to their mothers for up to eight years. This prolonged developmental phase offers a rare opportunity to study parenting over an extended timeline. The researchers focused on six maternal behaviors critical to the safety and social learning of the infants: staying close, body contact, carrying, initiating proximity, feeding nearby, and terminating contact.
While all mothers gradually gave their infants more space as they matured—a natural progression in development—the rate and extent of these changes differed from one mother to another. Some remained more hands-on well into their offspring’s later juvenile stages, while others encouraged independence earlier.
“These differences hint at what we could call maternal personality,” says senior author Dr. Caroline Schuppli. “We’re seeing not just flexibility in behavior but consistency in individual styles of caregiving.”
What makes this study especially significant is that such consistency suggests a deeper cognitive or emotional basis to orangutan parenting—potentially shedding light on the roots of human maternal behavior. Could personality in mothering be an evolutionary trait, not exclusive to our species but shared with other great apes?
The researchers are cautious about drawing conclusions too soon. While the findings confirm individual variation in maternal behavior, it remains unclear whether these differences affect the outcomes of infant development. Do more hands-on mothers raise more socially adept or independent young? Do infants learn differently depending on their mother’s parenting style? To answer these questions, researchers say they’ll need another decade of follow-up data.
This study adds to a growing body of evidence that nonhuman animals, especially great apes, are far more individually complex than once believed. It challenges the idea of uniform “instinctual” mothering in primates and opens the door to examining maternal care as a nuanced, personal expression—even in the rainforest.
As the scientific team continues their work in collaboration with Universitas Nasional Jakarta (UNAS) and local field researchers, their findings underscore the value of long-term behavioral studies in the wild. “It’s only through patient, years-long observation,” says Schuppli, “that we can begin to uncover the hidden textures of animal life and the personalities that shape it.”
